HighRise Building Construction Profile

High-rise buildings in the course of history Technology of high-rise buildings Risk potential Insurance

High-Rise Buildings

Münchener Rück

Munich Re GroupM

ContentsPage Page

1 Introduction 4

2 High-rise buildings in the course of his-

tory, technology and the environment 8

2.1 Historical development 92.2 Architectural aspects and urban

development today 122.3 Financing models 142.4 Infrastructural aspects 172.5 Economic aspects 212.6 Social and ecological aspects 21

3 Technology of high-rise construction 24

3.1 Planning 253.1.1 Planners 253.1.2 Regulations and directives 253.1.3 Technical analyses and special

questions 263.1.4 Construction licensing procedure 263.1.5 Other constraints 293.2 Execution 313.2.1 Foundations 313.2.2 Supporting structure 353.2.2.1 Load-bearing parts 353.2.2.2 Special construction methods 423.2.2.3 Facade 453.2.2.4 Roof 463.2.3 Interior finishing 463.2.4 Service systems 483.2.4.1 Installations 483.2.4.2 Deliveries, vehicles 493.2.4.3 Passenger transport, vertical

development 493.2.4.4 Waste disposal 503.3 Occupancy 513.3.1 Maintenance, administration 513.3.2 Conversions 533.3.3 Rehabilitation 533.4 High-rise construction in the future 54

4 Risk potential 84

4.1 Design errors 854.2 Fire 864.2.1 Examples of losses during the

construction phase 864.2.2 Fire protection on construction sites 894.2.3 Examples of losses during the

occupancy phase 994.2.4 Fire-protection regulations, loss

prevention 1074.2.4.1 Regulations 1074.2.4.2 Structural fire protection 1074.2.4.3 Active loss-prevention measures 108

4.2.4.4 Fire fighting 1104.2.4.5 Organizational measures 1114.2.4.6 Atriums 1114.3 Windstorm 1114.4 Earthquakes 1154.5 Foundations, settlement and

subsidence 1194.5.1 Foundations 1194.5.2 Settlement and subsidence 1214.6 Water 1224.7 Special structural measures 1224.7.1 Conversions 1224.7.2 Rehabilitation 1224.7.3 Demolition 1234.7.4 Disposal 1264.8 Other risks 1264.8.1 Terrorism 1264.8.2 Impact 1274.8.3 Collapse 1324.8.4 Wear 1324.9 Loss of profit 132

5 Insurance 138

5.1 Property insurance 1395.1.1 Contractors’ and erection all risks

insurance 1395.1.2 Advance loss of profit insurance 1415.1.3 Insurance of contractors’ plant

and machinery 1425.1.4 Decennial liability insurance 1445.1.5 Insurance of buildings, fire insurance 1445.1.6 Loss of profit insurance 1455.1.6.1 Loss of rent 1455.1.6.2 Additional costs 1455.1.6.3 Contingency planning 1455.1.6.4 Prevention of access 1455.2 Third-party liability insurance 1475.2.1 Insurance of the designer’s risk 1475.2.2 Insurance of the construction risk 1475.2.3 Insurance of the operational risk 1485.3 Problem of maximum loss 1495.3.1 Construction phase 1495.3.2 Decennial liability insurance 1495.3.3 Operating phase 1495.3.4 Accumulation control 1525.4 Underwriting considerations 1535.4.1 Contractors’ and erection all risks

insurance 1535.4.2 Contractors’ plant and machinery 1535.4.3 Decennial liability insurance 1535.4.4 Insurance of buildings, fire insurance 1535.5 Reinsurance 155

6 Summary and outlook 156

1 Introduction

1

1 Introduction

1 Introduction

From their beginning in the middle of the last century and right up to the present day, high-rise buildings havealways been a dominant landmark in the townscape, visible from far and wide, like the towers of Antiquity andthe Middle Ages. At the same time, this sky-scraping con-struction method has always been an ideal means of dis-playing power and influence in the community. In the lightof this goal, reasonable economic considerations often recede into the background during the erection and sub-sequent use of these high-rise buildings.A prestige object for the builder, these edifices not onlyhave an effect on their immediate neighbours, but also influence many areas of urban life in very different ways.These aspects will also be taken up in this publication.In the early years, the builders’ urge to rise to dizzyingheights was limited by unsolved technical problems. In recent years, however, a real competition has developedamong the builders of skyscrapers to be world championat least for a few months before being outdone by a rivalwith an even higher building. Even seemingly Utopianprojects now stand a good chance of becoming reality.This rapid development has only become possible be-cause the technical conditions and methods used in con-structing high-rise buildings have improved decisively and in some cases changed fundamentally in the last fewyears.

Up until the end of the last century, high-rise buildingswere still made of solid brick masonry, which ultimatelyrequired foundation walls up to 1.8 m thick. When steelframes adapted from steel bridge construction were intro-duced, with their increased strength and lower weight,builders and architects were able to soar to greaterheights. With this steel skeleton, the net weight of thestructure was considerably lower than that of a solid masonry building; it thus not only cut the costs of con-struction, but also gave wings to the architects’ imagin-ation. By the turn of the century, they were designing build-ings that also looked light and delicate as even at that time the skeleton structure permitted a large proportion of windows on the outer facade.

Since then, the construction of high-rise buildings hascontinued to change with the requirements imposed byair-conditioning and particularly office communications.The high-rise office buildings of the nineties have little in common with their predecessors. Instead of compact walls and ceilings, we now have a high-tech structure made up of largely prefabricated elements whichare welded and bonded together on site. The buildingcomprises a skeleton of steel or reinforced concrete whichis rounded off by suspended ceilings and false floorscreating the space required for installations. The originally

High-rise buildings have always triggered major debates and aroused emotion. That is hardly surprising, considering that this type of building radiates more symbolic power than almost any other.

1 Introduction

load-bearing outer wall has been replaced by a pre-fabricated facade.However, this complex method of construction promotesthe spread of fire and fumes, and therefore, in conjunctionwith the considerable concentration of values involved,represents an extremely sensitive risk both during con-struction and throughout the service life of the building. The major fires which broke out in a number of high-riseoffice buildings shortly before their completion in the earlynineties show how correct the appraisal of the fire risk inhigh-rise buildings is. The losses incurred through thesefires are several times higher than the amounts of indem-nity known to date. This is consequently one of the main reasons why high-rise buildings constitute a new dimension of risk for theinsurance industry, one which has made it necessary todraw up new concepts for underwriting, loss assessmentand PML determination throughout every phase of con-struction and subsequent use.We therefore believe that this publication on high-risebuildings is an appropriate addition to our comprehensiveseries of special publications, particularly those on under-ground railways and bridges.We are fully aware of the fact that many of the aspectsconsidered with regard to the construction, use and insur-ance of high-rise buildings naturally apply in the case oflower buildings too. Nevertheless, we do not wish to limitourselves to aspects which only apply specifically to high-rise buildings. After a brief historical overview, we willtherefore consider in detail all the risks and problems

associated with high-rise buildings and the techniques thatare applied in order to illuminate possible solutions fromthe point of view of both construction technology and insurance.

Moreover, the more broadly based general informationavailable will make it easier not only to assess the risk ofhigh-rise building projects but also to arrive at a price for insuring such projects.The definition of a high-rise building differs from onecountry to the next. For our purposes, we will proceed on the basis of a minimum height of 30 m and will restrictourselves to buildings used for residential or office pur-poses.Despite the various critical voices raised, the constructionof high-rise buildings has by no means reached its zenith.The problem of high-rise buildings is one which we – asinsurers and reinsurers – will also have to consider in thefuture.This special publication is also intended, last but not least,as a means of passing on to others our experience fromthe major losses that have occurred in the recent past.

02 SAN GIMIGNANO

03 MONADNOCK BUILDING

2 High-rise buildings in the course of history, technology and the environment

22.1 Historical development 2.3 Financing models 2.5 Economic aspects

2.2 Architectural aspects 2.4 Infrastructural aspects 2.6 Social and ecological aspects

04 THE TOWER OF BABEL


2.1 Historical development

What could be a more appropriate point to begin our con-sideration of high-rise buildings than with the Tower ofBabel and then to trace their historical development overthe centuries. However, a distinction must be madebetween “high buildings” and “high-rise buildings”: “highbuildings” have only a few floors and not uncommonlyonly one, albeit very high floor. They are crowned by ahigh roof and turrets (in the manner typical of medievaland Gothic cathedrals). “High-rise buildings”, on the otherhand, have many, usually identical floors of normal heightone above the other. Seen in this light, high-rise buildingshave their origins in the towers of San Gimignano ratherthan in the Tower of Babel or ecclesiastical structures.The first high-rise office building according to this defin-ition was built in Chicago in 1885: the Home InsuranceBuilding. It still stands on the corner of La Salle andAdams Street, a witness of its times. It has twelve floors –there were originally ten, but two were subsequentlyadded – and was built in roughly eighteen months. Thearchitect W. L. B. Jenney used an uncommon new methodfor the construction of his building: the weight of the wallswas borne by a framework of cast-iron columns and rolledI-sections which were bolted together via L-bars and theentire “skeleton” embedded in the masonry.The early Equitable Life Building in New York, which wascompleted in 1872, also contributed towards the develop-ment of high-rise buildings, for it was the first tall buildingto have an elevator. Although it only had six floors, the

edge of the roof was no less than 130 feet (roughly 38 m)above the road surface. Due to its elevator, the upperfloors were in greater demand than the lower floors. Fol-lowing completion of the “Equitable” building, it was thedone thing to reside on one of the “top” floors.Burnham and Roof’s Monadnock building, which wascompleted in Chicago in 1891, must also be mentioned asone of the last witnesses of a whole generation of solidmasonry high-rise buildings. Sixteen floors of robust brickmasonry rise skywards in stern, clear lines: an astonishingsight to eyes accustomed to the frills and fancies of thelate 19th century. Standing on an oblong base measuring59 m � 20 m, the building is reminiscent of a thin sliceand not only recalls the industrial brick buildings of thelate 19th century, but also anticipates the formal simplifi-cation of the later 1920s.The buildings rose higher and higher with the spread ofpioneering construction methods – such as the steel skeleton or reliable deep foundation methods – as well as the invention and development of the elevator. Thehighly spectacular skylines of North American cities, particularly Chicago and New York, originated in the earlyyears of the 20th century.Glancing over Manhattan’s stony profile, the silhouettesdotting the first 12 km of the 22-km-long island bear vociferous testimony to this dynamic development:– the World Trade Center, currently the tallest building in

New York, 417 m high,– the legendary Empire State Building, built in 1931,

381 m,

According to the Bible, the Tower of Babel was to “reach unto heaven” (Genesis 11).But when the Lord saw what the people had done, He confused their language and scattered them abroad over the faceof all the earth so that they left off building the city.


Top left: 05 EQUITABLE LIFE BUILDINGBottom left: 06 HOME INSURANCE BUILDING

Right: 07 NEW YORK PANORAMA

2 High-rise buildings in the course of history,

technology and the environment


– the United Nations building erected in 1953, 215 m, – the Chrysler Building dated 1930, 320 m, – the former Pan Am Building completed in 1963, 246 m, – the Rockefeller Center (1931–1940), a complex of

19 buildings,– the Citicorp Center built in 1978, 279 m, and– the AT&T Building opened in 1984, a pioneering

building by the post-modern architect Philip Johnson,with an overall height of 197 m.

It is only recently that attention has also turned to interest-ing high-rise buildings outside North America: NormanFoster’s Hong Kong and Shanghai Bank, Ieoh Ming Pei’sBank of China in Hong Kong and the twin tops of the Petronas Towers in Kuala Lumpur, currently the tallestbuilding in the world at 452 m.High-rise buildings in Germany are a modern develop-ment and are concentrated particularly in Frankfurt amMain: today, Frankfurt is the only German city with a skyline dominated by skyscrapers. One of the tallest build-ings in the city is the Messeturm built in 1991 with aheight of 259 m, which is not much more than half theheight of the Sears Tower in Chicago, currently the tallestoffice and business tower in North America with a totalheight of 443 m.It was the rapid growth in population that originally pro-moted the construction of high-rise buildings. New Yorkonce again provides a striking example: land becamescarce well over a hundred years ago as more and moreEuropean immigrants streamed into the city. From roughlyhalf a million in 1850, the city’s population grew to 1.4 million by 1899.More and more skyscrapers rose higher and higher on the solid ground in Manhattan, as buildings could only beerected with great difficulty on the boggy land to the right and left of the Hudson River and East River. In thisway, New York demonstrated what was meant by “urbandensification” despite the considerable doubts originallyvoiced by experts in conjunction with this development.The first area development code to come into force inNew York was the so-called “zoning law” of 1916, accord-

ing to which the height of a building must not exceed two-and-a-half times the width of the road running alongsidethe building. The building mass was further limited by therequirement that the floor space index must not exceedtwelve times the area of the site. Among other things, thezoning law stipulated that only the first twelve floors of abuilding were allowed to occupy the full area of the siteand that all subsequent floors must then recede in zonedterraces – a requirement of major aesthetic significance,for this terraced form still dominates the silhouette ofAmerican skyscrapers today.All doubts as to the profitability of high-rise buildingswere set aside with completion of the Empire State Build-ing, the Chrysler Building and other skyscrapers in the1930s, for they would never have been built if they couldnot have turned a profit. Although rentals proceeded slow-ly at first when the Empire State Building was completedin the heart of the recession in the 1930s and it was there-fore known as the “Empty State Building” for many years,it subsequently generated satisfactory revenues once allthe premises had been let.

Cities in Europe and Asia grew horizontally and it wasonly when production and services acquired greater eco-nomic significance throughout the world and the price ofland rose higher and higher in economic centres after theSecond World War that they also began to grow vertically.Modern Hong Kong is a striking case in point: it encom-passes an area of 1,037 km2 (Victoria, Kowloon and theNew Territories), of which only one-quarter has been de-veloped, but with maximum density and impressive effi-ciency. Almost all the new buildings, office towers andparticularly residential towers in the New Territories havemore than thirty floors.

2.2 Architectural aspects and urban development today

As the historical development of high-rise buildings hasalready shown, the construction of edifices reaching higher

08 HONGKONGBANK 09 MESSETURM, FRANKFURT AM MAINHEADQUARTERS BUILDING, HONG KONG

10 PETRONAS TOWERS


and higher into the sky was – and to a certain extent still is – an expression of power and strength. This isequally true of both ecclesiastical and secular buildings:the power, strength and influence of entire families – i.e.their standing in society – is mirrored in the erection ofever taller buildings culminating in a battle to build. Thetowers of San Gimignano are one of the best preservedexamples of this development. In many North African cit-ies, too, this attitude has moulded the townscape for many centuries and will no doubt continue to do so in the future.

The names of the builders and architects have only beenknown since the high Middle Ages around 1000 AD. Theycreated new stylistic elements and added their “signature”to entire periods. Looking back, this makes it difficult forus today to decide whether these master craftsmenshaped the various stylistic developments or whether anumber of master builders only became so well known because their work reflected the contemporary fashiontrends most accurately. That still holds true today, the onlydifference being that tastes change very much more rapid-ly and “degenerate” into short-lived fashions. A buildingthat reflects the spirit of the times when it is finished canappear “old” within only a few years. The brevity of thevarious stylistic trends is one of the reasons for the in-homogeneous appearance of modern towns and cities.Since architects must expect that later buildings will havetheir own, completely different formal identity, they do notsee any reason why they should base their own designson existing standards, particularly as this would merelycause them to be considered “unimaginative”.Three points become clear if we take a closer look at mod-ern trends in high-rise construction:– The dictate of tastes mentioned above is expressive of

the egotism prevalent in modern society with its desirefor status symbols and designer brands. Unfortunately,the public not uncommonly bows to this dictate, aswhen town councillors set aside major urban develop-ment considerations and with seeming generosity setup public areas in the form of lobbies and plazas inhigh-rise buildings.

– The sheer magnitude of the projects forces all plannersto adopt a scale totally out of proportion to all naturaldimensions and particularly to the people concernedwhen planning their buildings. In the past, urban devel-opment plans were easily drawn up on a scale of 1:100or at most 1:200, a scale which could still be directly related to the size of a human being. With today’s high-rise buildings, however, a scale of at least 1:1000 is required simply in order to depict the building on paper.This is illustrated by the example of the Sears Tower in Chicago: completed in 1974, the Tower measures 443 m in height. Drawn to a scale of 1:2000, a humanbeing is represented by a minute dot measuring barely0.9 mm.

– In the past, it was the master builder and architect whodefined the construction and consequently the appear-ance of a building; today, on the other hand, technicaldevelopments determine what can and cannot be done;

the appropriate and basically essential symbiosisbetween engineering designer and artist has been aban-doned.

This critical discourse on the architectural, urban develop-ment and economic background is not basically to castdoubt on high-rise buildings as such, but it does illuminatesome of the facets that are central to considering the riskpotential inherent in high-rise buildings.This almost inevitably raises the question why high-risebuildings should have to be built in today’s dimensions.– One reason is indisputably the need for a “landmark”. In

other words, to express economic and corporate powerand domination in impressive visual terms. Nothing haschanged in this respect since the very first high-risebuildings were erected.

– The steadily rising price of land in prime locations andan increasingly scarce supply have made it essential tomake optimum use of the air space. Prices in excess ofDM 50,000 per square metre are not uncommon for landin conurbations and economic centres. Despite theirheight, however, high-rise buildings still occupy areas oftruly gigantic proportions: the ratio of height-to-basewidth of the cubes in the 417-m-high World Trade Cen-ter, for example, is 6:1.

– Connections to the infrastructure are improved by con-centrating so many people in such a small area. TheWorld Trade Center alone provides jobs for over 50,000people – that is the equivalent of a medium-sized town.All institutions of public life are united under a singleroof and the distances between them have been min-imized.

However, high-rise buildings do little to prevent land beingsealed on a large scale. The suburbs of modern Americancities are a prime example: as far as the eye can see, thelandscape is covered with single-family homes, swimmingpools and artificially designed gardens simply to providesufficient private residential land for all the people work-ing in a high-rise building occupying only a few thousandsquare metres.– Many of the techniques and materials which are also

used for “normal” buildings today would never havebeen invented and would never have become estab-lished if high-rise construction had not presented a challenge in terms of technical feasibility. Rationalized,automated sequences are beneficial to high-rise build-ings; at no time in the past were such huge buildingserected in such a short space of time. Short constructionperiods also mean shorter financing periods and conse-quently profits which partly compensate for the add-itional costs incurred in the construction and finishing ofthe building.

2.3 Financing models

The construction costs for high-rise buildings often runinto hundreds of millions of dollars. The owner of thebuilding will rarely be willing or able to bear these costs

11 HIGH DENSITY: HONG KONG SKYLINE

12 FLATIRON BUILDING, NEW YORK


without outside assistance. On the other hand, however,debt service and exhausted credit lines will then constricthis operative freedom. Alternative financing models aretherefore frequently sought; the best known models arebriefly outlined below.

LEASINGLeasing of buildings, particularly high-rise buildings, canto a large extent be compared with rentals. This alternativeis commonly chosen when a company finds itself in finan-cial straits and needs cash. Selling the building – often aprestige object in a prime location – to a leasing companyis of two-fold advantage to the company: firstly, it acquiresthe urgently needed capital, and secondly, it can continueto use the building in return for a monthly leasing feewhich, however, amounts to no more than a fraction of thepurchase price received.The composition of corporate assets is changed by such atransaction. This can be a disadvantage when new loansare needed, for the building is then no longer shown onthe assets side as a property secured by entry in the landregister.

BOTBOT stands for “build, operate and transfer” (there areother variations but these will not be discussed in furtherdetail here). In the case of this financing model, the ownerof the land places his land at the disposal of a contractorwho then erects a building on it, such as an office tower.The owner of the land can exert a certain influence on theplanning and intended use, but does not share in the con-struction costs. The contractor must organize the project’sfinancing himself, be it with own funds or with the aid ofloans (“build”).In return, the owner of the land waives all or some of theincome from occupancy of the building for a certainperiod of time, usually 25 years. During this time, thebuilder must obtain rents that are calculated to cover hisdebt service and draw a profit from the invested capital(“operate”). The builder’s risk with regard to rents anddebt interest is often considerable. At the end of theagreed occupancy period, both the land and the officetower become the property of the landowner (“transfer”).

There are differences between these financing models: al-though the BOT model grants the landowner the right toownership, he is for a long time excluded from occupancyof the property. With the leasing model, the high capitalinvestment required is transferred to the lessor and thefinancing costs are replaced by monthly payments akinto rent by the lessee.

DEVELOPERThe developer is a new profession born out of the explo-sive rise in construction costs which has been intensifiedby increasingly large buildings and structures. This wastriggered by urban renewal programmes and changes intax regulations for large construction projects for whichnew financing models were developed in the USA in thesixties and seventies.

The developer usually draws up what is known as a mas-ter plan for complete districts and then retains (usuallyprominent) architects to design the various components ofthe master plan independently of one another. The devel-oper then seeks to find tenants or lessees for the buildingwhich at this stage only exists on paper. Constructionwork begins when tenants or lessees have been found.La Défense in the Paris Basin is a typical example of sucha development.This suburb was created on the drawing board in the1950s. A dilapidated district was demolished and com-pletely redesigned. The traffic systems, such as Metro,urban railway, motorway and access roads were movedbelow ground level and covered by a concrete slab 1.2 kmlong.

Mostly office towers were erected on this slab with opensquares and green areas in between. The ensemble isrounded off by the Grande Arche de la Défense designedby the Danish architect Johann Otto von Spreckelsen andcompleted in 1989. The Grande Arche is a huge cubewhich is open on two sides with 37 office floors and aheight of 110 m equal to its ground lengths. All the capitalinvested on the site came from private sources and wascontrolled by a public-law community of interests.

In times of sluggish investment activity, however, it is notuncommon to find that only certain parts of the masterplan are actually realized. Originally planned as a homoge-neous townscape, the result is then nothing more than anunrelated fragment and areas that should have been filledwith life appear to be deserted and uninhabited instead. Inthe mid-nineties London’s Docklands provided a dramaticexample of such a development: the transformation of theWest India Docks built between 1802 and 1806 resulted inwhat was for a while the highest mountain of debt in theworld with the high-rise obelisk on Canary Wharf. Afterhaving consumed roughly US$ 3bn, the half-finished pro-ject was temporarily abandoned before finally being com-pleted and let following a variety of financial transactions.

2.4 Infrastructural aspects

The different fates of La Défense and Canary Wharf arenot (only) due to the extremely different planning periodsof 30 years (La Défense) and 8 years (Canary Wharf), butabove all to the manner in which the necessary infrastruc-ture for the two projects was tackled.In the case of La Défense, the entire necessary infrastruc-ture was completed before the construction work actuallystarted: underground railway lines and roads, servicesystems were all planned and built beforehand. As a re-sult, a fully functional and above all adequately dimen-sioned infrastructure was consequently available when thebuildings were taken into service. This made La Défenseattractive to investors and tenants alike; the new districtsoon pulsated with life as an economically sound basis forthe entire project.

13 LA GRANDE ARCHE

14 CANARY WHARF

15 TRADITIONAL AND MODERN BUILDINGS IN PEACEFUL CO-EXISTENCE


A jungle of political, economic and investment difficultiesmust be overcome for such prospective planning becausethe owner of the high-rise complex bears no direct respon-sibility for the large majority of these far-reaching infra-structural measures. The project’s progress is consequent-ly controlled by the municipal authorities, as well as bysupply and operating companies and not by the owner ofthe complex.The situation of Canary Wharf in London’s Docklands is exactly the opposite and proves that the La Défensetype of planning is the economically more appropriate approach, despite the associated delay in starting con-struction work and the longer preliminary financing required.A second City of London was to be created in the heart ofthe Docklands within the shortest possible space of time,with thousands of square metres of tailor-made officespace, hotels, shops and apartments for high-income ten-ants. A rail-bound fully automatic cabin railway known asthe Docklands Light Railway was to ensure the necessaryaccess.However, this transport system fell far short of meetingthe requirements, as its capacity was far too low and itlacked the essential connection to the London Under-ground. The road connections for private traffic and publicbuses were similarly inadequate. This made the Docklandsunattractive to both commercial and private tenants. AnUnderground link was finally built after extensive planningand at the enormous cost of roughly US$ 1.7bn; the roadconnections were likewise improved at the cost of almostUS$ 1bn. Only then did the precarious economic situationof Canary Wharf improve.As these examples show, almost every high-rise construc-tion project is doomed to at least economic failure if theinfrastructure is not considered, planned and actually in-stalled down to the very last detail.

2.5 Economic aspects

Hundreds of companies and thousands of people dependon the smooth operation of a high-rise building, from theone-man business of a newspaper vendor or shoeshinerand corporations with thousands of employees, such asbanks, brokers or global players with a daily turnover inthe order of several billions to radio, television and tele-communications companies which use the roofs and topsof high-rise buildings for the transmission and receivinginstallations. In addition, there are innumerable other busi-nesses and workers with their families whose economicsituation is directly or indirectly linked with the high-risebuilding. These range from transport companies andcatering firms to tradesmen under long-term contract inthe building.Nor should it be overlooked that even the municipal au-thorities and the service companies are also affected bythe “failure” of a high-rise building and that its effects canbe felt nationwide or even worldwide in the worst case. This scenario not only applies to such total failure as a

major fire or collapse of the building. Despite (or preciselybecause of) its size, a high-rise building is an incrediblysensitive and vulnerable system. Even a brief power fail-ure can result in operational and economic chaos. Thesame applies to outside disturbances in the form of strikesby public transport corporations or a malfunction in theunderground or urban railway system.

2.6 Social and ecological aspects

Criticism today focuses particularly on the social and eco-logical effects of high-rise buildings.The most commonly voiced reservations with regard tohigh-rise apartment blocks concern the social aspect. It isclaimed – and there are probably a number of studies toprove – that cohabitation in high-rise buildings does notwork as smoothly as in homogeneous, historically growndistricts with numerous small, manageable dwellings. Theanonymity suffered by the people in these “residential fac-tories” is criticized in particular – above all on account ofthe total isolation from other residents in order to avoidthe stress of permanent contact.Organic, homogeneous population structures with theirpositive effects on social conduct are rarely found and thecharge that high-rise apartment blocks are hostile to fam-ilies and children is consequently not entirely unfounded.Two diametrically opposed ghetto situations can easilyarise in high-rise apartment blocks: since the costs for con-struction and maintenance of these buildings are dispro-portionately high, correspondingly high rents must becharged, with the result that these blocks are more or lessreserved for the well-off, while the socially weaker classesare excluded. Conversely, however, high-rise apartmentblocks can rapidly cease to be attractive if compromisesare made with regard to the building quality, maintenanceor infrastructure on account of the high investment costsentailed. A building in disrepair will soon drive away the“good” tenants and become a slum.The ghetto situation is intensified when high-rise apart-ment blocks are built in newly developed fringe areas – faraway from cultural and social centres – on account of thehigh cost of land in inner city areas. It is not without goodcause that these areas are commonly referred to as “dor-mitory towns”.Studies have also proved beyond all doubt that criminalactivity is promoted by huge apartment blocks and particu-larly high-rise buildings. According to these studies, thisphenomenon is attributable to the anonymity of the resi-dents, as well as to the “pro-crime” environment with ele-vators, poorly lit corridors devoid of human beings, refusecollection rooms and bicycle garages, laundries and aboveall underground parking lots. It is a proven fact that con-siderably more murders, burglaries, muggings, rapes andother crimes are committed in such buildings than in resi-dential areas with smaller rented or private homes.Not only high-rise apartment blocks have a usually nega-tive effect on people’s social environment: office towersare equally disadvantageous. The vertical structure of the


buildings simultaneously underlines the vertical hierarchy:the location of the office space becomes an indicator of acompany’s “importance” and, if the company occupiesseveral or all the floors in a high-rise building, it may alsobe indicative of the employee’s standing in the company.The company’s top executives reside on the uppermostfloors with the best views; the floors below provide ashield and every employee can positively see the distancebetween himself and “them up there“. It is therefore notwrong to question whether high-rise office towers arereally appropriate to modern organizational structureswith their emphasis on team work and interdisciplinarycooperation.

Excessive energy consumption is a major shortcoming ofhigh-rise buildings and one which could possibly lead totheir demise one day. High-rise buildings are the farthestremoved from the ideal form as regards energy efficiency– namely the sphere, or the cube in the case of houses.That applies to both heating and cooling: some skyscraperfacades have to be cooled by day and heated by night inorder to avoid undue stresses and the resultant damage.The World Trade Center, for example, consumes some680,000 kWh/day electricity for air-conditioning duringperiods of strong solar irradiation; the Messeturm inFrankfurt burns up energy worth DM 40 per square metreof useful floor space for heating and cooling every month.A well insulated low-energy house, by comparison, usesenergy worth less than DM 1 per square metre. The “energybalance” of high-rise buildings is also poor in otherrespects such as the water supply, which usually onlyoperates with the aid of booster pumps, as well as in termsof the disposal systems and operation of the elevators, etc.From the point of construction economy in general, high-rise buildings will probably always be the poorest conceiv-able solution, from the particularly energy-intensive andtherefore expensive construction as such to the dispropor-tionately high demolition costs. Moreover, high-rise build-ings are made almost exclusively of materials which aconstruction biologist would take great pains to avoid,namely concrete, steel, light metal, plastics and a widevariety of chemicals.Although subjectively unaware of the fact, the residentsare frequently exposed to constant stresses in the form ofpollutant emissions and electrosmog. High-rise buildingsare sometimes described as microcosms; that is no doubtmeant in a positive sense, but the reality is different. Thepeople in a high-rise building are totally cut off from theworld around them, from wind and weather, from tem-perature, from smells, sounds and moods. They live in anartificial world.At the same time, however, the high-rise buildings alsohave a negative effect on the world around them, for theynot uncommonly generate air turbulence and downdraftsin their immediate vicinity; they can be a source of un-pleasant reflections and some adjacent areas remain per-manently in the shade. Illuminated facades and large glassfronts are a death trap for many birds.The people outside the high-rise buildings also often havethe feeling that they are being observed or threatened by

the possibility of falling objects. That fear is surely not en-tirely unfounded, for there have been cases in which partsof buildings, such as glass panes, have been torn out oftheir anchorage by strong winds and injured or even killedpeople on the street below.Our love-hate relationship with high-rise buildings is final-ly also revealed in such recent box-office hits from Holly-wood as “Deep Impact”, “Godzilla” or “IndependenceDay”. It seems that their directors simply cannot avoid thetemptation of reducing one of New York’s most beautifulbuildings – the Chrysler Building – to a smouldering heapof rubble with the help of floods, monsters or meteorites.As a result, these skyscrapers more or less become thereal stars of the film on account of their magic attractionand immediate recognizability.

16 CHRYSLER BUILDING, NEW YORK

3 Technology of high-rise construction

33.1 Planning 3.2 Execution 3.3 Occupancy 3.4 High-rise construction in the future


3.1 Planning

3.1.1 Planners

The complexity of the trades to be coordinated has be-come several times greater since then. Take, for example,the new block built for Südwest-Landesbank in Stuttgart:many disciplines and different experts were involved sole-ly in the project planning:– Architects – Planning engineers for the supporting structures (engi-

neering design and structural analyses)– Construction and site management (resident engineer)– Planning of the technical building services (particularly

heating, ventilation, sanitation, cooling and air-conditioning)

– Interior designers– Construction physics and construction biology– Planning and site management for data networks– Planning of the lighting and materials handling– Planning of the electrical and electronic systems– Planning of the facades– Surveying engineers– Geotechnology, hydrogeology and environmental

protection– Design of outdoor facilities and vegetation– Surveying of the actual situation in surrounding build-

ings

If we were to include all the contractors and specialists in-volved in the project as well, the list would probably beten times longer. And if we then consider that bankers,construction authorities, legal advisers and even advertis-ing agencies or brokers must also be coordinated in the

course of the entire planning and construction of a sky-scraper project, it soon becomes clear that highly profes-sional management is essential for such a project. Projectmanagement companies have come to play an increasing-ly important role in recent years as they take over the en-tire organization, structurization and coordination of con-struction projects. They act as professional representativesfor the client and embody the frequently voiced desire forthe entire project to be coordinated by a single partner.

3.1.2 Regulations and directives

The various laws, regulations, directives and standards inforce must be taken into account when planning and erect-ing a building. The planning engineers are also obliged toobserve what are known in Germany, for instance, as the“generally accepted technical rules for construction“; inother words, generally applicable technical and trade rulesmust be taken into account and observed in addition tothe standards and regulations.Although each country has its own regulations and dir-ectives governing the construction of high-rise buildings,they are all basically similar in content with a few differ-ences depending on the local circumstances. It is standardpractice in some countries to base the bidding and plan-ning phase for projects on foreign standards (particularlyon the American ANSI Codes and UL Standards, BritishStandards or the German DIN standards) or to include var-ious elements of these foreign standards in the nationalsystem of standards.As a rule, these regulations are primarily designed to en-sure personal safety and then to protect the buildingagainst damage and defects. In addition to the require-ments imposed by public authorities, there are also re-

Skyscrapers are gigantic projects demanding incred-ible logistics, management and strong nerves amongall concerned in their planning and construction. As long ago as 1928, the American Colonel William A. Starrett wrote that no peacetime activity bore greater resemblance to a military strategy than theconstruction of a skyscraper.



quirements imposed by insurance companies with the aimof ensuring greater protection for property. These require-ments can be classified in four groups:

FIRE PROTECTION AND OPERATIONAL SECURITY

Many of the construction regulations concern fire protec-tion. There can be many thousands of people in a high-rise building at any one time. If a fire breaks out, theymust all be able to leave the building in the shortest possible space of time and without risk of injury. This iswhy regulations concerning the number and execution of escape routes and fire escapes, fire compartments and the choice of materials must be observed (see Section 4.2.5).Operational security encompasses regulations governingthe safety of elevators and escalators, the execution ofstairs, railings and parapets or the installation of emer-gency lighting. Some regulations also include CO2 alarmsystems for underground parking lots; indeed, there areeven regulations governing the non-slip nature of floorcoverings in traffic areas, sanitary rooms and kitchens.

STABILITY AND CONSTRUCTION PHYSICS

The regulations governing the stability of a building areusually met by the requisite structural analyses. In add-ition to demonstrating the internal structural strength ofthe construction and safe transfer of loads to the subsoil,the stability calculations must also include possible de-formation due to thermal expansion, wind loads and liveloads or dead weight, for example. This is closely relatedwith demonstrating the safety of the construction, for in-stance by taking steps to limit the (unavoidable) cracks inconcrete elements.

PROTECTION AGAINST NATURAL HAZARDS

The regulations and directives governing protectionagainst natural hazards are usually closely associated withthe demonstration of stability. Windstorms and earth-quakes are the most serious natural hazards for high-risebuildings. As a rule, the assumed loads and design rulesfor the “load cases” of earthquake and windstorm will bespecified by the regulations in order to ensure that thebuilding will withstand windstorms or earthquakes up tocertain load limits. At the same time, this will serve to ruleout the risk of bodily injury due to falling parts of thebuilding, especially parts of the facade.

SOCIAL ASPECTS AND PROTECTION OF THE SURROUNDINGS

The regulations governing social aspects and protection ofthe area surrounding high-rise buildings are designedabove all to prevent any indirect risk or threat to people.Such regulations may concern planning aspects, such asthe minimum distance between a high-rise building andneighbouring buildings, or they may take the form of rulesdefining the maximum permissible influence that a build-ing can have on the microcosm surrounding it.Depending on the location of the high-rise building, cor-responding statutory instruments may also govern theeffects on air traffic safety or the building’s influence ofradio communications.

This exceedingly concise outline of applicable regulationsilluminates only some of the rules to be observed whenbuilding a skyscraper. If all the regulations governing high-rise construction were to be stacked one on top of theother in printed form, they would themselves be as highas a multi-storey building.

3.1.3 Technical analyses and special questions

Planning a high-rise building would be inconceivabletoday without the help of experts and technical consult-ants. Extensive soil analyses are required to determine thestrength of the subsoil before deciding on the location fora high-rise building. In the majority of cases, cores aredrilled into the load-bearing subsoil to obtain soil samples.The drilling profile of the geological strata making up thesubsoil and laboratory analyses of the soil samples pro-vide the basic data for the soil report which is in turn usedas the basis for planning the supporting structures andchoosing a suitable foundation structure with due regardfor the loads exerted by the high-rise building. The forces acting on the high-rise structure in the event ofan earthquake must be taken into account when erectinghigh-rise buildings in areas prone to seismic activity. Thesame applies to wind loads and particularly to the dynamiceffects of windstorm or earthquake loads. The additionalvibration loads can result in overall loads of the sameorder of magnitude as the load exerted by the deadweight of the structure. The situation is particularly criticalif the vibrations reach the resonant frequency of the build-ing: in such a case, the vibrations can intensify until theentire building collapses. The collapse of the TacomaBridge in Washington State, USA, was probably the mostspectacular case of destruction due to resonant vibrationin a man-made structure.In many cases, these effects cannot be determined by or-dinary computation. Even computer simulation cannot al-ways help. Sometimes a decisive element may be lackingto obtain a mathematical approximation; in other cases,the computer may be too slow or the storage capacity in-adequate.This frequently makes it necessary to carry out modelexperiments in a scientific laboratory. Models of the high-rise buildings are exposed to artificial earthquakes on a vi-bratory table or subjected to a simulated hurricane in thewind tunnel. A detailed knowledge of mathematics andphysics is necessary to ensure that the same physicalproperties and serviceable results are obtained despite thereduction in scale. For this reason, these studies can onlybe carried out by highly specialized test institutes.

3.1.4 Construction licensing procedure

The construction licensing procedure is normally specifiedin the construction laws of the country concerned. As arule, the principal will file an application with all the requis-ite documents (description, plans, analyses, etc.) to the relevant construction supervisory authority. The involve-ment of specialists is obligatory in the case of larger andmore complicated projects, such as those involving high-

17 DETAILS FROM PLANNING DOCUMENTSNext page: 18 EXTRACT FROM A TECHNICAL REPORT


rise buildings. Such specialists include experts from themunicipal fire brigade, water authorities, trade supervisoryoffices, environment protection agencies or similar officesin other specific fields.These specialists review the applications for a constructionlicence and specify any additional requirements to be met.The licence is then sent to the principal together with therequirements specified by the specialists; responsibility forcomplying with these requirements rests with the principalor owner of the building.

3.1.5 Other constraints

Even in our high-tech era, the planning and constructionof a high-rise building are not dictated only by naked fac-tual constraints. Tradition, religion and even the belief inspirits and demons still play a not insignificant part inmany countries.Take, for example, the Hong Kong and Shanghai Bankbuilding in Hong Kong: during the planning phase, a geo-mancer or expert on “fung shui” (i.e. “wind and water“)repositioned the escalators and moved executive officesand conference rooms to the other side of the building onthe basis of astrological investigations and measurementsin order to guarantee an optimum sense of well-being forclients and employees. However, it must be said that suchintervention is limited by technical and structural require-ments.In western countries, too, the owners are guided by similar considerations when the 13th floor is omitted from the planning or the technical installations are deliber-ately located on this floor in order to avoid the unluckynumber 13.

19 OPENING IN AN APARTMENT COMPLEX ALLOWING NEGATIVE VIBES TO PASSTHROUGH


3.2 Execution

3.2.1 Foundations

Although the foundations are out of sight once the build-ing is completed, they are of immense importance for en-suring that the dead weight and live loads of the buildingare safely transmitted to the native subsoil.These loads are not inconsiderable. The dead weight of ahigh-rise building can amount to several hundred thou-sand tonnes. This value may be exceeded several timesover by the live loads which are taken as the basis for de-signing the building and include the loads from equipmentand furnishings, people or moving objects, as well as windor earthquake loads. Moreover, these loads often exert dif-ferent pressures on the subsoil, thus resulting in unevensettlement of the building. In order to avoid such develop-ments where possible, these buildings must be erected onsubsoil of high load-bearing capacity, such as solid rock.Yet even if a strong native subsoil is found near the sur-face, shallow foundations will frequently be disregarded infavour a system that transfers the load to deeper layers onaccount of the high bending moments to be absorbedfrom horizontal forces.This can be done in several ways. One is to produce roundor rectangular caissons which are lowered to the requireddepth and bear the foundation structure. Pile foundationsare probably the most widely used method, however. Thepiles can either be prefabricated and then inserted in thenative soil or they can be produced on site in the form ofconcrete drilling piles. Which method is chosen will ultim-ately depend on both the structural concept and the soil

conditions prevailing on site. Drilling piles in a whole var-iety of forms can be used when working with large pile diameters and very long piles. Modern equipment caneasily ram piles measuring up to 2 m in diameter todepths of well over 50 m. The piles are then combinedinto appropriate pile groups in accordance with the loadsto be transmitted by the building.Although the load-bearing capacity can be roughly calcu-lated on the basis of soil characteristics, the maximumpermissible pile load is determined by applying test loadsto the finished piles with the aid of hydraulic presses andcomparing the resultant settlement with the permissiblesettlement.Diaphragm walls are another means of producing deepfoundations. These walls are produced directly in theground and are between 60 and 100 cm thick. They areproduced in sections with the aid of special equipmentand a stabilizing bentonite slurry. The result is a continu-ous wall in the ground. This method is used in particularwhen subsoil of high load-bearing capacity is only foundat considerable depth. Diaphragm walls and piles are also used to safeguard thefoundation pit required for construction of the under-ground part of the building. The effort entailed can be con-siderable, particularly if the neighbouring buildings arevery close. Rotating drills are mostly used today to minim-ize vibrations when installing the retaining wall. Founda-tion pits can easily be produced to depths of 30 m or moreusing this method.

20 LARGE-BORE PILE FOUNDATION PROCESSBottom: VARIOUS STAGES IN THE DIAPHRAGM WALL PROCESS21 Following page: DIAPHRAGM WALL ROTARY CUTTER


22 RETAINING WALL TO PROTECT NEIGHBOURING BUILDINGS

23 VIEW OF A BUILDING PIT WITH COMPLETED RETAINING WALL


3.2.2 Supporting structure

3.2.2.1 Load-bearing parts

The steel skeleton permitted hitherto inconceivable flexi-bility in construction and layout planning. It also permittedseries construction up to great heights, since the verticaldead weight was considerably lower than when usingsolid masonry and did not make it necessary to grade thesectional steel profiles in these areas. The tradition of steelskeleton structures predates the first high-rise building tohave been erected by this method, namely the Home In-surance Building in Chicago (1885): mills and granaries, aswell as engineering structures (bridges, silos) had alreadybeen built in England with an iron framework towards theend of the 18th century.The first frame structures used for the steel skeleton were flexurally rigid frames corresponding in height toone floor. New York’s Empire State Building, which wascompleted in 1932, is one example which clearly shows the advantage of this new method, namely the short time required for the construction work. Moreover, thecomplete separation of outside wall and supporting structure permitted absolute freedom of design for the facade. Instead of requiring around 300 kg of steel persquare metre of base area as in the past, modern support-ing structures only require roughly 125 kg of steel on average.As the buildings became taller and taller, however, themain problem was no longer the vertical loads but suchhorizontal loads as wind and earthquake forces, as well astheir transmission.This led to the development of what was known as thecore method. The individual floors with their secondarysupporting structure, namely the columns, are suspendedfrom a central core as the primary supporting element,normally in the form of a reinforced concrete or steelstructure with reinforcing shear walls. The columns merelytransmit vertical loads, while the core transmits both verti-cal and horizontal loads. Its primary function is to rein-force the building in horizontal direction. The cores andtheir surrounding walls normally accommodate verticalservice installations, such as elevators, stairs, primary ser-vice shafts for electric power and HLS (heating, lighting,sanitation). A similar supporting effect is obtained with theaid of horizontal reinforcing elements in the form of shearwalls, which may be considered as an “open core“. How-ever, such supporting structures are rarely found in tallerbuildings.Since the middle of the 20th century, a number of im-provements in the supporting structures for skyscrapershave been introduced by the architects Skidmore, Owings& Merrill (SOM) in Chicago. One such development bySOM is the “outrigger truss”: a rigid superstructure knownas the outrigger is mounted at the top of a reinforcing corewith movably connected floors and columns. The outrig-ger connects the columns to the core. They are suspendedfrom the outrigger and are therefore under tension, thuseliminating the risk of buckling that is associated withpressure elements. A supporting system in the form of

such an outrigger truss yields further advantages over asimple core construction when it comes to transmission ofthe horizontal loads. The bending stress applied to thecore area in the lower floors is considerably reduced whenusing an outrigger truss. The outrigger itself usually ac-commodates such technical floors as the heating and ven-tilation systems.The Fort Wisconsin Center built in Milwaukee in 1962 isone example of an outrigger truss structure. The produc-tion of such suspended structures gave rise to a numberof innovations, such as the lift-slab process for concretestructures. The load-bearing cores are first of all erectedwith the outrigger on top; the individual floors are thenconcreted on the ground, one above the other (separatedby a release spray). Finally, they are raised to their installa-tion position by means of hydraulic jacks and then con-nected to the core (see Section 3.2.2.2).Supporting steel structures in the form of tubes are oftenused for extremely tall buildings. In this case, the support-ing structure is located in the outer facade, which is conse-quently designed in the form of a load-bearing facade withsmall openings. The result is an enclosed, intrinsicallyrigid tube without any unnecessary space-filling columnsinside. The World Trade Center in New York is an exampleof such a structure. The outer walls are studded with verti-cal steel columns roughly one metre apart. A generouslydimensioned development area was obtained on theground floor by “collecting” the descending columns.America’s tallest skyscraper, the Sears Tower in Chicago(443 m high), is a further development of the conventionaltube: it is a “bundled” tube. The layout of the building issubdivided into a number of tubes to relieve the columnsin the corners of the building when subjected to horizontalloads; this results in more uniform distribution of the loadover the facade columns. In this case, however, the inter-ior can no longer be designed with the same flexibility aswhen using a single tube.The “truss tubes” perfected by Fazlar Khan (SOM) in theJohn Hancock Center in Chicago are another further devel-opment of the basic tube. These tubes are additionally re-inforced by diagonal struts in the facade plane and are astructural feature that has almost become a hallmark ofSOM buildings.It was only in the mid-1970s that concrete began to bemore widely used in constructing skyscrapers. Until then,the length of time required for concrete construction andthe associated financing problems were the main reasonsfor the predominant use of steel structures in the construc-tion of high-rise buildings. New developments in shutter-ing, however, resulted in dramatically shorter constructiontimes. The octagonal concrete core of the Messeturm inFrankfurt, for example, was erected with the aid of a slip-form which was hydraulically raised one metre every day.The latest developments in supporting structures for high-rise buildings include composite structures of steel andconcrete, for instance in the form of steel sections embed-ded in concrete.

24 EXAMPLES OF HIGH-RISE BUILDINGS WITH STEEL SKELETONS

25 DEFORMATION AND BENDING MOMENTUM DUE TO WIND WITH THE CORE CONSTRUCTION METHOD

26 Background: COMMERZBANK BUILDING

27 DEFORMATION AND BENDING MOMENTUM DUE TO WIND WITH THEOUTRIGGER TRUSS METHOD

Below: 28 EXAMPLES OF CORE CONSTRUCTION METHODS (A-E) AND BUNDLED TUBES (F-G)

A B C D E F G


29 VARYING LOAD DISTRIBUTION WITH TUBES AND BUNDLED TUBES

� Wind


Top: 30 EXAMPLE OF THE ARRANGEMENTOF BUNDLED TUBES

Right: 31 STEEL SKELETON


3.2.2.2 Special construction methods

BMW HEADQUARTERS, MUNICH

The headquarters of BMW A.G. differs from conventionalbuildings to create an impressive corporate symbol in theform of a 100-m-high four-cylinder structure. The require-ments for appropriate office organization yielded a basicoutline in the shape of a clover leaf. Stairways, elevatorsand sanitary areas are accommodated in the central core.In this way, all the offices can be reached by the shortestpossible route. Trendsetting methods were also used forthe construction work.

A reinforced concrete version was chosen as the most economical solution. According to the design concept, theentire building with 18 office floors and a technical floorwas to be suspended from a girder cross at the top of theroughly 100-m-high core via four central king posts. This isa modification of the outrigger truss (Section 3.2.2.1). Theentire load of the building is transmitted to the founda-tions via the core as the central element; it also absorbs all wind forces. A mighty girder cross with a projection of16 m is mounted at the top of the core.The four king posts are secured to this central girdercross, each king post comprising 105 threaded steel barswith a load-bearing capacity equal to a suspended weightof 4,600 Mp. Small outer columns are additionally locatedbetween the floors. These outer columns are designed ascompression columns above the technical floor (12thfloor) and as king posts below.Time and costs were the decisive reasons for choosingthis innovative construction method. All 19 floors weresuccessively produced at the foot of the shell and core; thefirst floors were even produced complete with facade and

glazing during construction of the supporting cross. Thefinished floors were then connected to the supportingcross via the king posts and raised one floor at a timeevery week with the aid of hoisting gear so that anotherfloor could be produced in the space vacated at the foot ofthe core and then connected to the floor above (lift-slabmethod). Completion of the facade, glazing, installationand interior finishing proceeded on the suspended floors,unimpeded by the structural works and lifting operations.In addition to reducing the construction time required, thismethod also eliminated the need for expensive toolingand assembly work.

LA GRANDE ARCHE, PARIS

This building, which has already been mentioned in Sec-tion 2, takes the form of a giant cube open on two sideswith edge lengths of 110 m. It was completed at the end of1989 on the 200th anniversary of the French Revolutionand took 5 years to build (see photo on page 18).The building has a weight of more than 300,000 Mp and ismounted on neoprene bearings, the loads being transmit-ted 30 m into the subsoil via twelve concrete pillars.The cube’s main support is in the form of four prestressedupright reinforced concrete frames 21 m apart. They arecomplemented by horizontal members measuring roughly70 m at ground and roof level. Each of these members is9 m high, the equivalent of a 3-storey building. Since thetwo vertical sides of the cube would be without roof-leveltransverse bracing during construction, the required stabil-ity for that phase of the work was produced by means ofhorizontal steel truss reinforcements.A total of 37 office floors are accommodated in the two 18-m-wide wings of the cube (each with an area of42,000 m2).

Top: VIEW FROM THE HEADQUARTERS BUILDINGBottom: 32 HEADQUARTERS OF BMW A.G. IN MUNICH


3.2.2.3 Facade

The skeleton construction which has increasingly beenused since the turn of the century has inevitably given riseto new possibilities for the facade. The size, shape andnumber of windows were no longer limited by structuralrequirements following the introduction of curtain facades,since the loads were now primarily transmitted by postsand columns.

PLANNING

Most facade designs today are still based on empiricalknow-how and are not tested until the design has been established in detail. The tests are carried out on true-to-scale models of individual facade elements in order to test adequate resistance to air and water, load-bearing capacity and the possibility of excessive deformation or glass breakage when subjected to corresponding loads,e.g. with the aid of firmly anchored aircraft engines.

DESIGN

Today’s modern facades are characterized by external wallelements equal to one floor in height and insertedbetween the respective structural floors. Non-supportingmetal facades suspended in front of the building have in-creasingly become established for economic reasons, par-ticularly in high-rise construction.The scope for design is enlarged by coloured or mirroredwindow panels and linings of natural stone, ceramic tiles or brick. Almost any desired appearance can be pro-duced.

TECHNICAL PROPERTIES

Modern facades must meet complex requirements as re-gards construction technology, engineering design andconstruction physics. Thanks to its lightness and almostunlimited possibilities for profile design, aluminium haslargely become the material of choice for the outer frame-work. The panes are made of high-grade glass filled withnoble gases or with a surface coating that reflects infraredlight. On the inside, modern facades are highly imperme-able to water and water vapour in order to prevent dam-age due to moisture.Despite the large areas of glass, protection against the sunis more important than heat loss today due to good ther-mal insulation of modern facades. Even where sound-proofing and fire protection are concerned, glass and

metal facades are at least the equal of conventional con-structions.Modern facades also require a sophisticated ventilationand cooling system. The air-conditioned or twin facade isa case in point. Here an additional facade of laminatedglass is arranged in front of the conventional facade, thuscreating a space through which air can circulate. Morecomplex ventilation concepts for routing air into and outof the building may be realized by including additionalvertical and horizontal bulkheads. Individually controlledventilation flaps are capable of providing a more naturaland far less complex exchange of air.

PRODUCTION AND ASSEMBLY

Due to the extensive know-how required with regard tomaterial properties and construction physics and on ac-count of the great manufacturing depth, modern facadesare only produced by specialized companies based on thearchitect’s design and in accordance with functional, aswell as structural aspects before subsequently being as-sembled.The degree of prefabrication in modern facades is consid-erable. The frames, glazing, parapet lining, sunshades andanti-glare finish, as well as thermal insulation and sealingare all assembled into single-storey facade elements in themanufacturer’s plant. In many cases, such technical equip-ment parts as radiators, air outlets and the ducting forelectrical and electronic equipment are also already inte-grated at this stage. In the meantime, fixing elements can be mounted on theshell of the high-rise building. These elements can usuallybe displaced in three planes to compensate the dimen-sional tolerances occurring in the shell. The facade elem-ents as such are fitted without the help of scaffolding, thus greatly reducing the time required for this work. Theframe profiles are assembled with labyrinthine indenta-tions to compensate the deformation arising in the build-ing as a result of wind and live loads, as well as tempera-ture differences. Permanently elastic rubber profiles en-sure that the facade remains impermeable to air andwater.

33 FACADE ASSEMBLY


3.2.2.4 Roof

There are no fixed rules governing the roofs of high-risebuildings. The roof design depends only on the architect’sdraft and on the purposes and functions to be fulfilled bythe roof.Most roofs are flat. The electromechanical drive systemfor the elevators is usually installed on the roof; in somecases, there is also a rail around the perimeter of thebuilding to accommodate the equipment required forcleaning the facade, as well as the pertinent connectionsand facilities.A heliport or parking space can also be set up on the flatroof of large high-rise buildings. It is sometimes even usedin Japan for golfing practice.Air-intake towers for air-conditioning systems, on theother hand, have become less common on modern high-rise buildings. Due to the great height of buildings, air-conditioning and heating systems are now decentralizedand spread over several individual floors. Moreover, everyinstallation and every superstructure on the roof meansanother opening in the intact roof skin and this can giverise to leakage problems, particularly on flat roofs. It istherefore advantageous to transfer such systems to lowerfloors.Overhead glazing is another type of roof commonly foundin high-rise buildings. Such roofs keep out the elementswhile at the same time creating spacious assembly areas,usually in the centre of the building. Atriums and conven-tion halls are two pertinent examples.High-rise buildings with a sloping roof are usually round-ed off by an antenna system with appropriate lightningprotection.

3.2.3 Interior finishing

Walls, ceilings and floors in high-rise buildings are no dif-ferent to those in other buildings. The choice of materialsand structures depends on the intended use of the build-ing rather than on its form (high-rise, low-level or cubic).Since particular importance is attached to flexible use ofhigh-rise buildings, the partition walls, floor structures and(usually suspended) ceilings will be of corresponding de-sign.When considering the interior finishing, a distinction mustbasically be made between load-bearing or supporting ele-ments which are required for structural reasons and thosewhich merely partition off the rooms and installations.Load-bearing elements are almost exclusively made ofconcrete or steel today, as well as of combinations ofthese materials.

Due to the relatively small area available per floor, fire-resistant elements (fire walls) are usually only to be foundin the core areas incorporating the elevators, stairwells,service and installation shafts, sanitary and ancillaryrooms. A vertical breakdown into fire compartments ismostly obtained with the aid of fire-resistant floor con-structions (for further details see Section 4.2.4).The installations for air-conditioning, ventilation, lightingand fire alarms are usually located between the load-bear-ing ceiling and a suspended false ceiling into which thelamps are normally integrated. Small-scale electrical in-stallations are contained in trunking in the screed flooring;elevated false floors are installed if numerous connectionsare required, such as in computer centres. Cables can thenbe routed as desired in the space below the floor; theequipment is connected to sockets in so-called floor tanks.False floors are to be found almost everywhere in modernoffice towers, since cables can be rerouted without diffi-culty, as is increasingly required on account of the rapidpace of change in office and communications technology.Moreover, the space below the floor can also be used forventilation and air-conditioning installations, particularly incomputer centres. Particular attention must be paid to thequestion of fire protection in such false floor construc-tions.Connection of the flexible partition walls to both the sus-pended ceiling and the elevated false floor can pose prob-lems. From the point of view of soundproofing and ther-mal insulation, it would be better to install the partitionwalls between the load-bearing floors. However, since thesuspended ceilings and false floors normally extend overthe entire area and are not confined to any single room onaccount of the technical installations, the partition wallsmust also be fitted between the suspended ceiling andfalse floor. This consequently makes it necessary to usesoundproofing and thermally insulating floor coverings,as well as ceiling materials.Facade elements into which technical components havealready been incorporated by the manufacturer (see Section 3.2.3) are conveniently linked to the remaining net-work by means of screw-in and plug-in connections. How-ever, it is becoming increasingly rare for such technicalservice connections to be installed in the external walls,as they do not permit as flexible use of the room as floortanks.

34 CEILING INSTALLATION35 DOUBLE FLOORING


3.2.4 Service systems

3.2.4.1 Installations

ENERGY AND WATER SUPPLY

Unlike the case with normal multi-storey buildings, thetechnical service components in high-rise buildings mustmeet special requirements – if only on account of theheight – since the required supply of energy, water and airand the effluent volume are incomparably larger. The twintowers of the World Trade Center in New York, for in-stance, with around 50,000 employees and 80,000 visitorsevery day, requires more than 25,000 kWh of electricityevery hour. These utilities must also be transported to thevery last floor in sufficient quantities, under adequatepressure and at sometimes totally different temperatures.The planning effort required on the part of the service en-gineers responsible for the supply and disposal services inhigh-rise buildings is therefore very much greater than in the case of smaller and medium-sized projects. Thecosts for electrical and electronic systems in the recentlycompleted Petronas Towers in Kuala Lumpur, currently thetallest building in the world, amount to more than US$ 90 per square metre – and that does not include any otherservices.The pressure load on the individual components is re-duced through subdivision into several pressure stageswith technical service centres in the basement or on theground floor, on intermediate floors and on the roof.

VENTILATION AND AIR-CONDITIONING

The systems should be designed in such a way as to en-sure flexible division of the areas (large rooms, individualrooms) so that their use can subsequently be changedwithout extensive conversions.A variety of ventilation and air-conditioning systems canbe installed, depending on the purpose for which thebuilding is used. The high-rise headquarters of the Deut-sche Bank in Frankfurt am Main, for instance, is supplied bya two-channel high-pressure system in which the air is in-jected from above and discharged through correspondingexhaust air windows. A second, independent two-channelhigh-pressure system additionally blows air into therooms from the false floors.The concept used in the Messeturm in Frankfurt am Mainis completely different: in this case the required air is sup-plied via what is known as a one-channel continuous-flowsystem in combination with a “fan-coil four-conductorsystem” in the outer facade.In principle, all air-conditioning and ventilation systemsmust meet the same basic requirements:

– The air in the room must be continuously renewed (athree to sixfold exchange of air is normally required perhour).

– The outside air flow must be guaranteed with a min-imum fresh air flow of 30 to 60 m3/h per person.

– The risk of drafts must be minimized and any nuisancedue to the transmission of sound eliminated.

– It must be possible to shut off individual plant segmentswhen the corresponding parts of the building are not inuse.

SUPPLY OF HEAT AND COOLING

Unlike the case with the majority of normal multi-storeybuildings in which the installed heating capacity is severaltimes the required cooling capacity, the ratio is normallyreversed completely in most high-rise buildings, dueabove all to the larger ratio of window area to total ex-terior area.The energy required for this purpose, such as heating,steam, refrigeration and electricity, must be supplied withdue regard to cost-efficiency and the minimum possibleenvironmental impact due to emissions. A number of alternative solutions are drawn up during the planningphase and compared in order to determine the most cost-efficient source of energy on the basis of the investmentcosts and expected annual costs for operation and main-tenance of the equipment.The essential difference between high-rise buildings andother buildings in terms of designing the components(particularly fittings, pumps, gaskets) lies in the higherpressure stage. A water column in a 300-m-tall building,for instance, exerts a stagnation pressure of 30 bar. Thefittings on the lower floors must therefore be dimensionedfor the maximum stagnation pressure (possibly with theaid of pressure reducers). This makes for a major differ-ence in costs.

SANITATION

Pressure stages are also required for the sanitation, thuspermitting the use of smaller pumps. Sanitary dispensingpoints must additionally be isolated from the building assuch for soundproofing reasons.The internal heat loads (e.g. hot exhaust air, exhaust heatfrom refrigeration systems) accumulated in high-risebuildings are commonly used to heat water with the aid ofheat pumps or heat recovery systems.Studies undertaken in the USA have shown that the heightdoes not have any effect on the flow rate and rate of fall,since faecal matter and effluent do not simply drop to theground under the force of gravity, but more or less windtheir way downwards along the pipe walls.

CONTROL SYSTEMS

Today’s complex, ultra-modern control systems are pri-marily based on intelligent digital controllers. This tech-nology permits a direct link between DDC (direct digitalcontrol) substations and the centralized instrumentationand control which also takes over energy managementfunctions, such as:– optimization of the overnight and weekend temperature

reduction,– linking the heating of service water with re-cooling of

the refrigeration system, – operation of the external blinds.


3.2.4.2 Deliveries, vehicles

Although most high-rise buildings are centrally locatedand within a convenient distance to public transportsystems, a sufficient number of parking spaces must stillbe provided for employees, suppliers and visitors. Thenumber of parking spaces required is usually stipulated inthe construction regulations in relation to the number ofjobs or useful office space; similar ratios also apply toother business premises, shops, restaurants and meetinghalls. The ratio may be more than 5:1 – i.e. one parkingspace for more than five jobs – if the building is well sup-plied by public transport, such as direct connection to theunderground railway. Even in such cases, however, sev-eral hundred or a few thousand parking spaces may stillbe required for large high-rise buildings. The recently com-pleted Petronas Towers in Malaysia, for instance, is set toaccommodate around 70,000 workers. In extreme cases, ifadequate public transport is not available, it may be ne-cessary to provide one parking space for every job.

For financial reasons, the size of a high-rise building isoften also dictated by the number of parking spaces re-quired. Depending on the nature, location and executionof the garages and on the building’s structural system (na-ture of the subsoil), the manufacturing costs for one park-ing space can easily amount to around DM 50,000. Thismeans that the cost of building 2,000 parking spaces canreach as much as DM 100m with complex engineering andlocation on several levels, including the required rampsand traffic areas.Traffic links must be created not only for the parking spaces, but also for delivery traffic to the building, as well as for refuse-collection vehicles. High-rise buildingsare commonly said to represent a “town under one roof“. That, however, also means that the traffic to, around and from the building is equal to that of a smalltown, the only difference being that the entire traffic isconcentrated on a handful of access roads and adjacenttraffic areas which must be able to handle this volumeof traffic at peak periods.

3.2.4.3 Passenger transport, vertical development

In addition to escalators and automatic walkways, whichusually only serve to connect a few floors convenientlyand without delays, passengers and goods are normallycarried up and down by elevators in high-rise buildings.The comparison made above between a high-rise buildingand a small town also applies with regard to the numberof people inside the building: in the course of a few hoursevery morning, tens of thousands of people stream into amegabuilding to start work and leave again within a veryshort space of time at the end of the day. They are supple-mented by visitors, guests and customers, with the resultthat the elevators often have to transport well over100,000 people every day.

It is therefore not unfair to assert that the American invent-or of our modern “safety elevator”, Elisha Graves Otis,was also one of the pioneers who paved the way in 1852for high-rise construction. Asked what they feared most ina high-rise building, the respondents claimed that theirgreatest horror scenario was not a fire, but a malfunctionin the elevator system. Such catastrophes may be exceed-ingly rare, but they cannot be excluded entirely. A fully oc-cupied elevator plummeted when a B25 bomber crashedinto the Empire State Building in 1945 (see Section 4.8.2).In the beginning, when the high-rise buildings had nomore than about 20 floors, every elevator led from the en-trance level (not necessarily the ground floor) to everyother floor in the building. The simple control technologywas offset by a number of disadvantages: numerous ele-vators and elevator shafts were needed. The numerousstops and, above all, the low speed (with frequent brakingand restarting) meant that it took a long time for the eleva-tor to reach its destination. It was soon found that eleva-tors – like every mass transit system – needed a sophisti-cated operating concept. The two operating systems com-monly used today – namely group and changeover opera-tion – only became possible with the development of powerful drive systems and controllers, as well as highlyeffective braking systems with multiple braking for safetyreasons.In group operation, for which a separate shaft is (still) re-quired for each elevator, the elevators or groups of eleva-tors only serve certain floors: one group of elevatorsserves the first ten floors, for example, while a secondgroup serves floors 10 to 20 from the entrance level, thenext group then serves floors 20 to 30, etc. The groupsmust overlap on at least one floor so that people cantransfer from the 17th to the 23rd floor, for example, al-though they must change elevators in the process. The advantage of this system is that the number of elevatorshafts decreases towards the top of the building, thuscounteracting the lower floor space frequently found onthe top floors.In changeover operation, large and very fast express ele-vators serve a small number of central floors which areoften also highlighted architecturally. In New York’s Em-pire State Building, these elevators take no more than aminute to travel from the ground floor to the 80th floor.“Local elevators” serve the floors between the “change-over floors“. Here too, the elevators may serve groups offloors in exceptionally large high-rise buildings. If theequipment rooms are located alongside the elevator shaft,a number of local elevators can be operated one abovethe other in the same shaft; in this way, the number ofshafts can be reduced while maintaining the transport capacity. Up to three elevators are contained one abovethe other in each of 36 open shafts in New York’s WorldTrade Center. The volume of traffic is analysed by micro-processors, thus avoiding long delays. The floor area hasbeen increased by 25% as a result of these sophisticatedsystems.


At least one goods elevator with high load-bearing cap-acity and therefore lower speed is usually required totransport goods and to serve the building. Depending on the size of the high-rise building, there must also be a sufficient number of elevator cabins largeenough to accommodate stretchers.Elevators should never be used to evacuate people follow-ing a catastrophe. It is therefore a statutory requirement inmost countries that a warning be affixed to all elevatorsprohibiting use of the elevator in the event of a fire. Eleva-tors are often directed automatically to the ground floorfollowing a fire alarm and remain there with their doorsopen. So-called firemen’s lifts are additionally installed inhigh-rise buildings for use in the event of a fire (see Sec-tion 4.2.4).Apart from the statics, there is no other structural part orequipment in a building subject to so many regulationsand technical controls as the elevator – and with good reason, too. Constant care and regular maintenance com-bined with stringent inspections by an independent test institution, such as the Technical Inspection Agencies (TÜV)in Germany, are an absolute must for the safe operation ofhigh-rise buildings.

3.2.4.4 Waste disposal

In the days when waste was collected without preliminarysorting on site, waste chutes were frequently installed inresidential and administrative buildings, as well as in high-rise buildings with up to 20 floors. Such waste chutes arenot advisable in taller buildings – due to the associatedgreater height of fall – for paper or plastic bags tear openas they fall and considerable noise is generated by thewaste as it falls and collides with the walls and bottom ofthe chute. The fire hazard is also enormous.Standard practice today is to collect the waste separatelyon each floor: paper, recyclable secondary materials, com-postable organic waste and residual household wastewhich is collected in large containers and then transferredvia the goods elevator (or service elevator) to a central col-lecting point (in the basement) alongside the delivery areaor to the underground parking deck. The waste is com-pressed to a fraction of its original volume in special con-tainers at the central collecting point. Mobile waste collect-ing bins are ready and waiting in the goods elevators inthe World Trade Center in New York, for instance. In add-ition, there are five filling hoppers which can comminuteall manner of objects, including desks.

36 ELEVATOR IN THE WORLD TRADE CENTER, NEW YORK


Too little attention is frequently paid to the problem ofwaste disposal when planning a building. The followingrough estimate illustrates just how much waste can accu-mulate in a high-rise building: if each of the 5,000 as-sumed employees in a high-rise building “produces” only2 kg of waste per day, that makes a total of no less then10 tonnes to be disposed of every day. In addition, there isthe waste from shops, kitchens and restaurants, as well asspecial waste from service facilities and filling stations formotor vehicles. A sophisticated logistical system is conse-quently needed simply to dispose of the waste.

3.3 Occupancy

3.3.1 Maintenance, administration

When the high-rise building is completed, it is taken intoservice and occupied by the owner or tenants. Costs arecontinuously incurred during this time for maintenanceand care of the building; these costs can have a significanteffect on the financial result of the building’s operator. Hemust decide whether to employ his own staff to deal withthe problems (e.g. cleaning, maintenance, security, admin-istration) or whether to assign intrinsic functions to exter-

nal service-providers (“outsourcing“). Both alternatives re-quire an efficient building management capable of takingover the following responsibilities, particularly in the caseof high-rise buildings:a) Technical building management – Energy supply – Disposal – Equipment operation – System communication b) Commercial building management – Cost accounting – Property accounting – Rentals – Contract management c) Infrastructural building management – Cleaning services – Caretaker services – Security services – Secretarial and postal services A new market segment known as “facility management”has developed in recent years and caters to the needs ofusers in larger properties in particular. It differs from clas-sic building management in that it is not limited solely tothe occupancy phase, but is already in action during theplanning phase and therefore covers the entire life cycle ofthe building right up to its demolition.

38 MAINTENANCE37 ELEVATOR DEMONSTRATION BY OTIS


Top: 39 RENOVATION OF A HIGH-RISE BUILDING

Bottom: 40 PILE-DRIVING MACHINERY FOR WORKING INBASEMENT FLOORS


Cost-efficient optimization of all processes during the occupancy phase of a high-rise building requires an effi-cient and powerful computer system including CAD (computer-aided design) applications. The latter is particularly important for internal planning changes, con-versions, rehabilitation and changes in occupancy, as wellas for permitting documentation of important information(e.g. layout drawings, general drawings of the building,security information, furniture inventories, telephone con-nections).New requirements are often imposed on the performanceof technical equipment in a high-rise building in thecourse of its occupancy phase. Different times of day andseasons, as well as changing tenants require rapid adapta-tion of the heat, cooling, electric power and lighting. In office buildings, manufacturing premises and high-risebuildings, this adjustment is handled by freely program-mable DDC systems which record all the data of the con-nected technical equipment, such as fans, burners, pumps,valves and external blinds, analyse these data and thenoptimize the corresponding process sequence. Unneces-sary energy consumption is avoided, consumers areswitched off when their offices are not in use andswitched on again shortly before occupancy recom-mences. The recorded data are forwarded to either thecentralized instrumentation and control in the building orvia the public telephone network to an external controlcentre. Expensive call-outs on site can be reduced through remote programming by the maintenance com-pany if faults arise or limit values change. If more com-plex maintenance work is required, the technician on dutycan immediately see which spare parts are requiredto remedy the fault.

3.3.2 Conversions

In the planning a high-rise building, care is normally takento ensure that the building can subsequently be used in arelatively flexible manner. Internal conversions due tochanges of use following a change of tenant or the chang-ing needs of the present user should not be a problem. Inthis way, the operator of the building can also respondmore effectively to changes in the property market.To ensure such flexibility, the service systems are centrallylocated in the building. The partition walls separating theindividual rooms are non-supporting and can be relocatedto permit subsequent changes in room size. As a rule, thebuilding’s supporting structure is totally isolated from thesystem of partition walls inside the building. Where pos-sible, reinforcing walls are located outside the useful floorarea, such as in the core area. The columns are conse-quently the only remaining load-bearing elements causinga “nuisance” in the useful area. A column spacing of 6 to7 m is widely used as a standard grid, meeting both archi-tectural and structural requirements.If the conversion nevertheless affects the load-bearingstructure of the high-rise building, it is essential to drawup a structural analysis for all building states during theconversion work in order to avoid damage. If other partsof the building remain in use during the conversion work,

special precautions must be taken and the work efficientlycoordinated to ensure that the conversion proceeds with-out a hitch.The only possibility for expansion in densely populatedcities is normally upwards – i.e. by adding floors – if add-itional space is required at a later date. In such cases, par-ticular care must be taken to ensure that the additionalloads can be absorbed by both the existing building andthe existing foundation structure. It may even prove ne-cessary to extend the foundations in such a case. This canbe achieved by a technically complex method using add-itional piles which must be produced with the aid of spe-cial drilling equipment in the underground parking levelson account of the low working height.Demolishing old skyscrapers in inner city areas is an ex-ceedingly complicated business. Such buildings are nor-mally demolished by blasting after months of preparationand a great deal of expert knowledge so that the explosivecharges are positioned at precisely the right points to en-sure that the building collapses like a stack of cards with-out a single piece of rubble leaving the site.

3.3.3 Rehabilitation

There are many reasons why a high-rise building shouldhave to be rehabilitated. The criteria to be met here arebasically the same as for conversions, i.e. the safety ofthe building and its residents or users must be assuredcompletely and at all times during the rehabilitation work.Particularly high safety standards must be maintained inconjunction with asbestos abatement – i.e. when removingthe asbestos installed as insulation or for fire-protectionpurposes and replacing it with physiologically safer materials. Asbestos fibres are considered to be highly carcinogenic and are released in particular during demolition work.The technical equipment in the building, such as heating,sanitation or elevators, must also be rehabilitated after acertain period of time. In many cases, however, such re-newal or modernization work is undertaken without shut-ting down the entire building. It is often sufficient to shutdown only part of the building, and sometimes the workcan even be carried out without interrupting operation ofthe building at all.


In view of the anticipated population explosion andthe concentration of dwellers in the conurbations, the need for high-rise buildings will continue to grow,especially with building land becoming increasinglyscarce and property prices soaring as a consequence.The Australian Embassy in Tokyo sold 500 m2 of itsgarden in return for DM 1.25m – per square metre!Such astronomical prices can be more easily understood if we consider that there are currently5,400 people per square kilometre in Tokyo and that the population in this conurbation is forecast to increase from 18.5 million at present to almost 30 million in the coming decades. In some regions, it will only be possible to settle new residents or busi-nesses if they can be accommodated in high-risebuildings.

It is already certain that today’s (1999) world record for thetallest building – the twin Petronas Towers in Kuala Lum-pur (452 m) – will not be held for long. A new record-breaking edifice, the Chongqing Tower, is already underconstruction in Shanghai. Specific plans have alreadybeen drawn up for an 800-m-high building in Tokyo (Mil-lennium Tower), and totally inconceivable, gigantic pro-jects involving heights of several kilometres are also underdiscussion. One of the most unusual is the Japanese pro-ject TRY 2004, a pyramid rising 2004 m into the sky. It is to be made up of 204 octahedral elements which can bemutually sealed off from one another if a fire breaks out.In this way, living space is to be created for one millionpeople over an area of 8 km2.Economic considerations could impose limits on these gi-gantic plans, for the costs for construction and operationof a high-rise building increase exponentially with its

height. It does not take a prophet to forecast that the future of high-rise buildings – these “architectural dino-saurs”, as one critic recently wrote – is highly uncertain intheir traditional form. The disproportionately large manu-facturing effort, the high operating costs due above all tothe excessive consumption of energy, and reservations asregards health and safety will result in a new kind of high-rise building totally different from today’s.Since technological progress is advancing steadily, how-ever, and the attitudes of both owners and architects willalso be of decisive importance, one would almost requirethe skills of a clairvoyant to predict with any accuracy thespecific changes which are impending. Nevertheless, weshall at least venture a rough prediction of possible futuredevelopments.

3.4 High-rise construction in the future

41 PETRONAS TOWER


MESSETURM259 m

LANDMARK TOWER296 m

CENTRAL PLAZA310 m

EMPIRE STATE BUILDING381 m

JIN MAO BUILDING381 m

42 TREND TOWARDS EVER-TALLER MODERN HIGH-RISE BUILDINGS


ASIA PLAZA431 m

SEARS TOWER443 m

PETRONAS TOWERS452 m

CHONGQING TOWER457 m (under construc-tion)

MILLENNIUM TOWER800 m (planned)

800m(2624 feet)

43 THE MILLENNIUM TOWER – a vision for the 3rd millennium

452(1482 feet)

2

22m

44 PETRONAS TOWERS, KUALA LUMPUR, MALAYSIA

443m(1453 feet)

45 SEARS TOWER, CHICAGO

381m(1250 feet)

46 EMPIRE STATE BUILDING, NEW YORK

259m

47 MESSETURM IN FRANKFURT AM MAIN

(850 feet)


48 ADDITIONAL HEAT RECOVERY VIA PILING FOUNDATIONS IN THE COMMERZBANK HIGH-RISE BUILDING

ENERGY SAVINGS

Consistent use of the savings potential already availabletoday will indisputably be the most important “source” ofenergy in the future. Numerous studies have proved thatenergy savings of up to 80% can be realized in both theprivate and the commercial sector without any loss ofcomfort or convenience. “Intelligent energy consumption”is a term that is increasingly being used in this context. Asa result, the foundations for a building’s future consump-tion of energy are already set in the planning stage: thetopographical surroundings are of importance here, as isconsideration of the prevailing wind strengths and direc-tions, and any shadows cast. An energy-efficient buildingwill be positioned with its “broadside” away from the sunin warmer climates, while every effort will be made to ensure that as much of the facade as possible faces thesun in colder climates. Windows facing the sun should beas large as possible, those facing way from the sun assmall as possible (the keyword is: passive solar architec-ture). A rotary building is another conceivable possibilityand could be turned towards or away from the sun as re-quired. Particular attention must be paid to thermal insula-tion of the facade. Northern European construction stand-ards are a positive example here, as they specify a thick-ness of several decimetres for the insulating layers. Trans-parent thermal insulation will probably become estab-lished in future, as it not only reduces the heat loss, butcan also attract additional heat by allowing the radiatedheat to reach the facade without obstruction. Thermopaneglazing with a k-value of less than 1 already represents thestate of the art today, as does solar glazing with almost100% reflection of the radiated heat.Considerable savings can also be achieved inside thebuilding, for instance by using a combined heat andpower generating unit instead of conventional heat andpower generation, or by using variable-speed forced-circu-lation pumps in the sanitation, heating and air-condition-ing sectors, or by using energy-efficient fluorescent tubeswhich require up to 80% less electricity than conventionalfilament lamps, or by controlling the lights via movementdetectors and naturally by ensuring the energy efficiencyof every single appliance used in flats or offices, from well insulated fridges to personal computers with lowpower consumption. Reusing the off-heat from air andwater will be a matter of greater importance in the future.Ideally, our future energy requirements should all be metby regenerative sources.

POWER GENERATION

High-rise buildings are positively ideal for generatingpower: the huge facades are usually exposed to the sunfrom dawn to dusk and the prevailing winds on the roofare considerably stronger and more persistent than thoseon the ground. And these are also the main sources of en-ergy to be used in the future: wind-operated plants to gen-erate electricity on the roof or particularly exposed edgesof the facade, collectors to heat air or water and photovol-taic systems to generate electricity on the facades andpossibly also for producing hydrogen at a later stage.Generation of heat via the deep-pile foundations asso-ciated with virtually every high-rise building is a less ob-vious possibility. When the building is complete, watercan be circulated through heat exchanger tubes integratedinto the pile reinforcements. Due to the feed and returnflow of the water, the different energy potential betweenfooting and building can be exploited and the subsoil used as a seasonal or temporary store of energy. One of the first projects of this type has already been realizedin the rebuilding of the Commerzbank headquarters in Frankfurt am Main.

CONSTRUCTION BIOLOGY

The more we know and learn about the harmful effects ofmodern materials and installations on health, the lessprobable it becomes that future generations will voluntar-ily accept this hazard. Research and industry must there-fore find acceptable alternatives, such as emission-freematerials, installations, insulating and isolating materials,adhesives and coatings, as well as avoiding the use ofchemicals which give off toxic gases in the event of a fire.


49 FULLY AUTOMATED BUILDING SITE

CONSTRUCTION PRACTICE

The construction of high-rise buildings will be dominated by four factors in future, namely: time savings, personnel savings and financial savings, in addition to the energy savings already mentioned above.As examples in Japan show, it is already possible to erect buildings with the help of assembly robots. The required ele-ments are designed and drawn with the aid of computers (CAD = computer-aided design). The computer automaticallyretrieves all the required (dimensional and design) data from the saved architectural and engineering drafts, as well asfrom detailed libraries. The parts are then manufactured by fully automatic machines on the basis of these productiondata (CAM = computer-aided manufacture) and transported to the site “just in time“. Assembly robots pick out the rightpart in the right sequence, transport it to the assembly point and install the finished element in the right place.

Thanks to the efficiency of the computers and robots,buildings erected in this way bear little resemblanceto the conventional edifices erected with prefabricatedparts: the precision and arithmetic accuracy of thesemachines permits a hitherto inconceivable variety offorms and even the most complex structural analysesare mastered with the help of computers.

If the engineers who developed and built these robot-controlled “construction machines” are to be believed, then thismethod can not only considerably cut the time required for construction work, but can also reduce the construction costsby up to 40% and reduce the workforce required for conventional construction projects by up to one-third (roughly one-half of these would then find work in the component manufacturing plants). Above all, the dangerous and physicallystrenuous work would be eliminated.In this way, something that was considered Utopian only a few years ago has already begun to become an everyday real-ity: huge edifices and even complete towns are erected by robots as if guided by a ghostly hand. In spite of this, how-ever – or perhaps for precisely this reason – highly qualified experts will be needed to develop, operate and control thenecessary computer programs, techniques and technologies.

50 JIN MAO BUILDING

51 SHANGHAI PUDONG

52 NEW YORK53 CHINA, GUANGZHOU

54 NEW YORK

55 NEW YORK: VIEW FROM THE WORLD TRADE CENTER

56 NEW YORK

4 Risk potential

44.1 Design errors 4.3 Windstorm 4.5 Foundations, settlement 4.7 Special structural measures 4.9 Loss of profit

4.2 Fire 4.4 Earthquakes 4.6 Water 4.8 Other risks

4 Risk potential

4.1 Design errors

Fortunately, no-one really knows just how many rumoureddesign errors by architects are actually true. They are saidto have forgotten not only the toilets, but even completestairwells in multi-storey buildings. And today’s construc-tion practice makes such design errors more probable thanever: since the supporting structure, shell and core, andinterior finishing are totally isolated from one another notonly during the design phase, but also during the subse-quent construction phase, errors may possibly not be dis-covered until the work has reached a fairly advanced stage.This leads to time-consuming and costly changes and cor-rections, usually at the expense of the professional indem-nity insurance prescribed for architects in many countries.The most commonly occurring design errors can be sub-divided into two groups: failure to observe building andplanning codes on the one hand, and errors in the choiceof materials and wrong or inadequate construction detailson the other.

FAILURE TO OBSERVE BUILDING AND PLANNING CODES

It may be assumed that, in the majority of countries, whena building exceeds a certain size – and this will certainlyapply to high-rise buildings – corresponding plans mustbe submitted to the construction licensing and supervisoryauthorities for inspection. The inspection and approvalprocedure not only encompasses aspects under the build-ing code, such as compliance with specified distances andthe specified height and size of a building or its type ofuse, but also the safety of the people inside the building.

Such aspects include compliance with fire protection re-quirements in the building, the position and number of escape routes and the number, location and execution ofstairwells and traffic areas. Even such seemingly less im-portant aspects as compliance with accident preventionregulations are reviewed, for instance as regards theheight of railings or the distance between bars in railingsand grids.In many cases, however, the design is changed at shortnotice during the construction phase, with the result thatthe plans submitted for inspection no longer reflect the actual situation. If errors are made by the designer at thisstage in violation of building and planning codes, they willonly be discovered (if at all) during final inspection of thebuilding by the construction supervisory authority as specified in many countries.Such changes frequently cannot be undone, and this forces both sides to accept compromises possibly at theexpense of the building’s safety. Despite the numerousstatutory instruments and court rulings in test cases, thecomplex legal relationship between principal and architectmakes it necessary for the courts to decide who is to bearthe costs incurred as a result of such errors. In most cases,both the architect’s legal protection insurer and his profes-sional indemnity insurer will be involved.If the errors are not discovered and the building is takeninto service, however, this may not only increase the prob-ability of a loss occurring, but also pose an acute risk tolife and limb for its users. Particularly grave defects onlybecome evident when the loss actually occurs, for in-stance when a fire occurs. Fire insurers, personal accident,

The following sections consider all of the hazards constituting the greatest risk potential during the construction and occupancy of a high-rise building.The commentaries will be illustrated by examples oflosses and rounded off by proposals which need to be implemented to minimize such risk potential andprevent losses.

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health and life insurers, occupational disability insurersand once again the liability insurers may all be calledupon to bear the costs once the courts have settled thequestion of blame. If a guilty party can be identified, thatparty can face considerable penalties for any shortcom-ings ascertained. It is irrelevant in this context whetherthis party was actually aware of these shortcomings ormerely must have been aware of them.For this reason, all insurers – and particularly fire insurers– are well advised to ascertain whether all of the safety re-quirements have been met before they conclude a policyfor buildings entailing high risk potential.

MATERIALS AND CONSTRUCTION DETAILS

Not only the legal relationship between principal and architect is exceedingly complex; just as complicated isthat between architect and (sub)contractors and particular-ly among the (sub)contractors themselves.Although the architect or specialist engineer specifieswhich materials are to be used or installed, the (sub)con-tractor must check whether these materials are indeedsuitable for such use. Modern and unconventional con-struction practices frequently make it difficult or even im-possible for (sub)contractors to determine whether thespecified materials or the execution intended by thedesigner are indeed suitable and correct.Unsuitable materials and connections in sanitary installa-tions, for instance, can rapidly result in water damage dueto burst pipes.Unsuitable insulating materials can give off toxic gases oracids in the event of a fire; incorrectly dimensioned fix-tures for suspended ceilings or facade elements can causebodily injury or property damage if they fall down.In extremely simplified terms, it could be said that most ofthe damage incurred in or on a building is ultimately at-tributable to design errors.

4.2 Fire

Fire is one of the greatest risks for every building and par-ticularly for high-rise buildings. Due to the spectacularphotographs and film sequences shown in the media,major fires have always made – and will continue to make – headline news not only during the constructionphase, but above all during the occupancy phase. They are a major headache to all insurers and reinsurers duein particular to the exorbitant rise in repair and restorationcosts, as well as the loss of human life.A few examples of major fires during the construction andoccupancy phases are provided below.

4.2.1 Examples of losses during the construction phase

GENERAL

It is not always easy for an insurer to determine whichrisks may be associated with technical improvements, newtechniques, new materials or combinations of differentmaterials. It is only when the loss occurs that the insurer

can be sure of having underwritten a completely new risk.As already mentioned in Sections 3.2.3 and 3.2.4, the con-struction of modern office towers has little in commonwith the construction methods employed in the past. In-stead of solid ceilings and walls, we now have a skeletonstructure – usually made of steel – with endless kilometresof wiring for telecommunications, switching, control andair-conditioning running vertically and horizontallythrough the entire structure. During both the constructionand the operating phases, this combination consequentlyposes an enormous risk for the spread of fire and smoke,as well as for the harmful effects of heat, fumes and water.

BROADGATE

This new 12-storey office tower is one of fourteen build-ings erected over the railway tracks of a station in the Cityof London. Due to the extremely confined conditions, thecontainers accommodating the construction workers wereinstalled on the first floor of the shell. During the evening of 22nd June 1990, an electrical appli-ance or short-circuit caused a smouldering fire in one ofthese containers. Undiscovered for several hours, thissmouldering fire charred the interior furnishings until itreached the polystyrene foam inside the steel walls of thecontainer. This resulted in major generation of smoke untilthe container literally burst apart around midnight andcaused a major fire.The fire was only discovered by a security patrol roughly30 minutes later after a smoke detector was tripped. Whenthe fire brigade arrived another seven minutes later, thetemperature around the container was apparently alreadyin excess of 1,100 °C. Twenty fire-fighting teams with over100 firemen fought for almost five hours to bring this diffi-cult fire under control.The extreme heat ultimately caused the steel skeleton anda number of ceilings to fail. A large area in the middle partof the roughly 40-m-high building subsequently droppedby between 0.6 and 1.2 m. The fire also destroyed materialwhich was stored on the first and second floors. This ledto even more intense smoke emission, which in turncaused extensive damage to the aluminium facade andvaluable interior fittings.The considerable property damage worth around £36mwas the highest fire loss to have been incurred in a high-rise building in the United Kingdom up to that time andwas due to the absence of an early-warning system, thewidespread propagation of fumes due to the chimney ef-fect of the atrium and the presence of numerous openingsin walls and ceilings. Moreover, neither the fire-alarmsystem nor the risers and sprinkler system had been acti-vated in this stage of the building’s construction.

LONDON UNDERWRITING CENTRE

A fire broke out during the interior finishing work in thisover 55-m-high office tower in London’s banking and in-surance centre in August 1991. The cost of repairing thedamage consumed £110m or around 75% of the insuredvalue of the building and was far higher than the cost ofrepairing the damage following the Broadgate fire in theprevious year. First estimates indicated that the loss would

57 FIRE IN THE BROADGATE BUILDING, LONDON: sunken roof support beams

Following page: 58 FIRE-PROTECTION INFORMATION

be no more than a fraction of the final cost, and to theman on the street the building appeared to have survivedlargely unscathed, at least from the outside, and merelyhad to be cleaned.The fire broke out on the ground floor at the beginning ofthe morning shift, near the atrium where it was extensive-ly nourished by the considerable material and packagingscrap which had been stored there. Although the fire bri-gade arrived within minutes despite the early morningrush-hour and narrow streets, it proved extremely difficultto bring the fire under control. Thanks to the atrium, theflames had already reached the roof and were reachingout towards the unsealed floors leading off to the sides.The atrium itself was difficult to reach since it was com-pletely encased in scaffolding for installation of 16 largeescalators. The stairwells were almost impassable on ac-count of the immense heat and smoke. It was only whenthe roof above the atrium broke and the smoke was dis-pelled that the firemen were able to make progress inbringing the fire under control.The considerable increases in the cost of repairing thebuilding during the ensuing months were due almost ex-clusively to the extreme spread of harmful fumes. Thesefumes (including chloride-laden fumes from burning PVCcable installations) had spread through openings in wallsand ceilings, as well as the false floors, to all floors aboveand below ground and had settled on most of the installa-tions and facade elements. Further damage was caused bycontaminated fire-fighting water in the false floors andbasement floors. The supporting structure, on the otherhand, suffered very little damage.In addition to requiring extensive decontamination, suchfires also raise questions with regard to warranties. Sup-pliers may have guaranteed the serviceability and appear-ance of their parts and installations over a period of sev-eral years, but no-one can judge how the frequently com-plex switchgear, for example, will respond over the yearsto the extreme heat and corrosive fumes produced by thefire. In addition, the commonly used PVC sheathing alsoproduces highly corrosive substances.

MERIDIEN PRESIDENT TOWER

This 36-storey hotel and shopping centre in Bangkok wasalmost complete and about to be inaugurated when a firebroke out following an explosion during installation ofparts of the air-conditioning. The fire very rapidly spreadthrough the air-conditioning shafts and soon reached the10th floor, as well as lower floors.When the fire broke out, more than 150 construction work-ers were adding the finishing touches to the inside of thebuilding. Since the workers on the upper floors were un-able to make their way downwards, roughly 40 fled ontothe roof while others used ropes to lower themselves ontoa veranda on the 5th floor so that they could escape fromthe flames.Despite the intense smoke, seven helicopters succeeded inrescuing the men on the roof, as well as another 50 fromlower floors with the aid of ladders and straps. One of thehelicopters was even forced to make an emergency land-ing after its tail rotor touched the building in the dense

smoke. Three men died in the fire or as a result of jump-ing out of a window.Altogether, 40 fire brigades with over 2,000 firemen foughtfor roughly six hours to bring the fire under control. Theirwork was impeded from the very beginning by the narrowaccess roads. The water pressure from their nozzles onlyreached up to the 10th floor.Subsequent investigations revealed that although all thefire-prevention requirements, such as smoke detectors,fire walls, firemen’s lifts and sprinkler systems, had beenmet, these systems had not been activated during the con-struction phase. It is assumed that the fire was most prob-ably caused by a bucket of thinners igniting on contactwith sparks from welding work being done on parts of theair-conditioning system.Despite the extensive damage, the hotel – which is locatedon the 17th to 36th floors of the building – was openedwithout undue delay. In the department store, around3,000 m2 out of more than 130,000 m2 was seriously damaged by the fire, but the supporting structures re-mained unscathed. Completion of the store is expected tobe delayed by several months. The total loss is estimatedto be in the region of DM 25m.

4.2.2 Fire protection on construction sites

Numerous similar major fires in the recent past have clear-ly shown that too little attention is still being paid to fireprevention on construction sites for buildings in generaland for high-rise buildings in particular. This has led todevastating fires and immense costs for the insurance in-dustry.These fires are more likely to be caused by human negli-gence than by technical defects, for example workers care-lessly throwing away glowing cigarette ends and the im-proper use of cooking appliances in the workers’ quarters,which are frequently located in the shell of the building.Moreover, as the fires in the Broadgate Building (1990)and the London Underwriting Centre (1991) clearlyshowed, an atrium in the building can have extremelynegative effects in the event of a fire, as its considerablearea positively invites misuse as a place for storing largequantities of material, particularly during the constructionwork. These materials are easily combustible on accountof their packaging, which is usually not removed before-hand and therefore constitutes an increased fire risk. In addition, the chimney effect (i.e. vertical draft) due to theatrium helps the fire to spread rapidly to the roof andother floors leading off from the atrium.The situation is further aggravated by the fact that, even ifthe risk potential is acknowledged, safety features are thefirst to be sacrificed under the rising pressure of time andcosts. The growing use of combustible materials, the high-er fire load and its distribution over all floors are thereforethe main reasons for catastrophic major fires.This trend has become unacceptable in the United King-dom. In an unrivalled campaign, fire brigades, insurancecompanies and the construction industry have drawn up a“Joint Code of Practice” for fire protection on constructionsites. Compliance with the regulations and requirements

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59 ESCALATOR DESTROYED BY FIRE

60 FIRE IN THE MERIDIEN PRESIDENT TOWER, BANGKOK

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61 MERIDIEN PRESIDENT TOWER, INCREASED RISK OF FIRE DURING THE FINAL FIT-OUT PHASE

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62 DIFFICULT FIRE-FIGHTING CONDITIONS IN THE MERIDIEN PRESIDENT TOWER

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contained in this Code has now become an indispensableelement in the terms of insurance for the construction ofmajor high-rise projects. This Code specifies in detail howfire protection is to be effectively organized and imple-mented in all the various areas and phases of construc-tion.Adequate protection against fires can only be guaranteedby clear instructions and standards which are implement-ed from the very beginning of the construction work andwhich are regularly monitored and supported with corres-ponding investments in time, money and material.Particularly in the case of high-rise construction, prevent-ive fire protection must be included from the planningphase onwards so that the various construction phasescan be taken into account accordingly. One of the essentialconditions for effective fire protection is the appointmentof a safety officer responsible for risk management on site.A whole team of safety officers may be appointed for ahigh-rise construction site; in such cases, they are often re-sponsible for personal and occupational safety, as well asfor fire protection. In addition to drawing up, implement-ing and verifying the fire-protection concept, it is import-ant to train the site personnel in fire-fighting techniquesand to familiarize the fire brigade with the site.Since the situation on site is subject to constant change inline with the progress made during the various construc-tion phases, the site drawings must be regularly updatedwith regard to access roads for the fire brigade, fire com-partments, water supply lines and fire loads in particularlyhigh concentrations. Such risks as combustible liquids,gas depots, cable ducts and temporary openings in wallsand ceilings must be highlighted in the same way as theavailable fire-fighting equipment.Above all, particular attention must be paid to preventivefire protection. The primary objective must be to reducethe fire load. Waste materials must be removed regularlyand combustible waste collected from the individual floorsevery day. The value of material stored for constructionand assembly work should be limited, the material spreadover several storage units and protected by special meas-ures, such as fire walls or sufficient distance, in order toreduce what is frequently a very high fire load.Specific control of all work constituting a fire hazard is an-other essential precaution. A special approval procedure isbeing introduced to ensure safer practices with grinding,cutting or welding work, for example, as well as work withsoldering lamps, application of hot asphalt or other workwith radiant heat. At least one person trained in fire-fight-ing techniques and equipped with a fire extinguisher mustalways be present during such work. Even when the workis complete, however, the area must be inspected again toensure that a fire cannot break out subsequently (e.g. as aresult of glowing welding slag).The site should be fenced off and access controlled inorder to minimize the risk of fires due to third parties.

4.2.3 Examples of losses during the occupancy phase

GARLEY BUILDING IN HONG KONG

“Elevator to hell”, “Trapped in a burning skyscraper”,“Towering inferno” – these are just a few of the headlinesin world press reports on one of the most devastating firesin Hong Kong in almost 40 years.During welding work in an elevator shaft in the 16-storeyGarley Building in Hong Kong’s Kowloon district on 21stNovember 1996, a fire broke out which killed 39 peopleand seriously injured around 80 others. More than 90 people were rescued, some of them in daring scenes inwhich a helicopter pilot risked his own life.Maintenance and repair work was in progress in the officeand business tower when highly flammable materialcaught fire during welding work in the basement. The firemade its way up through the elevator shafts and spreadlike lightning through the top three floors of the building.The immense heat and smoke made these floors a deathtrap for the people working there: the windows could notbe opened to let the heat and smoke out, and escaperoutes were filled with smoke or impassable on account ofthe fire. As a result, 22 charred bodies were subsequentlyfound in a single office on the 15th floor.The fire brigade was called shortly after the fire broke outand arrived on the scene shortly afterwards, so that manyof the people in the building were fortunately saved. Al-though hundreds of firemen were at the scene of the fire,it took over 20 hours to bring the fire under control.What were the reasons for the fire being able to spread sorapidly, for the magnitude of the loss and the numerousfatalities? The primary cause lay in the totally inadequatefire-protection installations in the 21-year-old Garley Build-ing. There was neither an automatic fire alarm nor asprinkler system. From the speed at which the fire spreadthrough the elevator shaft to the upper office floors, it maybe assumed that the structural fire protection was also in-adequate. It is claimed that plywood had been used asprovisional elevator doors.The Hong Kong Fire Prevention Act stipulates that all high-rise buildings licensed after 1973 must be equipped with asprinkler system, among other things, but this did notapply to the Garley Building. In view of the large numberof older buildings in a similar condition to that of the Gar-ley Building, the headline in one Hong Kong newspaper –“700 office buildings could become death traps” – is notso far-fetched.

FIRST INTERSTATE BANK BUILDING IN LOS ANGELES, USA

Once the tallest building in California, the 261-m-high, 62-storey office tower fell prey to what is considered tohave been one of the most destructive skyscraper fires inthe USA in recent years when, for reasons unknown, a firebroke out on the 12th floor on the evening of 4th May1988. From the fire-fighting point of view, it representedone of the biggest challenges for the Los Angeles City FireDepartment. With 383 firemen, almost one-half of the en-tire shift on duty in the city was called out to fight this fire.The fire was brought under control after 31/2 hours. The12th to 16th floors were gutted. The floors above suffered

63 COMBUSTIBLE WASTE INCREASES RISK OF FIRE

64 LIMITED EVACUATION ROUTES THROUGH SMOKE-FILLED STAIRWAYS

65 HONG KONG, FIRE IN THE GARLEY BUILDING

66 TOWERING INFERNO67 DIFFICULT FIRE-FIGHTING CONDITIONS

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considerable damage due to smoke and those below wereextensively damaged by fire-fighting water.One maintenance technician died when he took the eleva-tor to the floor in which the fire had broken out becausean open fire door had evidently jammed between theburning office area and the lobby in front of the elevator.Around 50 people were injured, including several firemen.The loss totalled more than US$ 50m, plus losses amount-ing to tens of millions for business interruption.The building had been completed in 1973 before thesprinkler regulation for high-rise buildings in Los Angelescame into force. This regulation stipulates that sprinklersmust be installed throughout the building. At the time ofthe fire, work was under way to install a sprinkler systemin the rest of the building to ensure better fire protectionfor the roughly 4,000 employees and tenants in the build-ing and to supplement the sprinkler system which wasoriginally only installed on the lower level of the under-ground car park. Work on the new sprinkler system was al-ready 90% completed at the time of the fire, even in thefloors affected by it, but the system had not yet been takeninto service. Parts of the riser had also been drained andfire pumps switched off in the building.The fire brigade was alerted by a neighbour, as there wasa delay before the alarm warned security personnel des-pite the fact that the automatic fire-detection system wasfunctioning correctly; this delay was due to human errorand incorrect regulations. As a result, the security person-nel disregarded a fire alarm triggered manually by the in-stallation workers in response to minor smoke emissions,as well as other alarms by smoke detectors on the 12thfloor.By the time the fire brigade arrived, most of the 12th floorwas already in flames. Since use of the elevators was pro-hibited by regulations, the firemen had to carry theirheavy equipment up the stairs to the scene of the fire. As a result, roughly half an hour passed before they wereactually able to start fighting the fire with water from therisers in the four stairwells.Fighting the fire proved to be a difficult matter. Onceagain, the excessively low water pressure had to be boost-ed with the aid of fire pumps and additional water sup-plied via the risers. Since the fire doors leading to thestairs had been opened, smoke and fumes soon spreadupwards.In the meantime, the fire had spread to floors above the12th floor with flames up to 10 m high leaping from broken windows on the outer facade. Fire and smoke alsopenetrated through incompletely sealed cable openingsand air-conditioning ducts, as well as through the 31 ele-vator shafts.In addition to the intense heat and smoke in the stairwells,the firemen’s work was further impeded by failure of thepower supply and of the emergency lighting in the stair-wells. The vital radio link was similarly impeded by theshielding effect of the building’s steel skeleton and thelarge number of firemen on the scene.Helicopters were called in to drop firemen onto the roof ofthe building to allow them to head down towards the seatof the fire via the stairwells. However, this attempt had to

be abandoned on account of the major smoke in the stair-wells with their chimney effect.Broken glass panes on the facade posed another problemas they fell down onto firemen and fire engines feedingwater into the fire connections at the foot of the building.Cut hoses had to be replaced more than once. The glasspanes also came down in large units, as they were bondedtogether by the reflecting plastic coating; even the coatingwas burning in some cases. As a precautionary measure, the newly installed sprinklergroups on floors 17 to 19 above the burning floors werealso activated so that they would have provided effectiveassistance had the fire spread above the 16th floor, butthis proved unnecessary.The defects and negative factors will be discussed in moredetail in the next section. The positive factors in this diffi-cult fight against a fire are summarized here:– Concentrated and well organized deployment of

firemen.– Resistant supporting steel framework thanks to the fire-

resistant spray-coating.– Sophisticated emergency plans by the bank made it

possible to continue bank operation without a hitch inan emergency centre on the morning following the fireand throughout the months of cleaning and repair workin the building.

– As a result of this fire, a regulation was issued specify-ing that sprinkler systems had to be retrofitted in all 450 high-rise buildings without such sprinkler protectionin Los Angeles within a transition period of three years.

ONE MERIDIAN PLAZA IN PHILADELPHIA, USA

On the evening of 23rd February 1991, a fire broke out onthe 21st floor of this office tower with 38 floors aboveground and three underground floors. Three firemen werekilled in action and 24 others injured.There were only a few people in the building when an automatic fire-detection system on the 21st floor triggeredan alarm on the central control panel on the ground floorat 20.23 hours. The fire brigade was called by neighboursbefore an alarm could be sent from there to the fire bri-gade.The first firemen arrived on the scene after seven minutesand took the elevator up to the 10th floor. From there, theytook the stairs up to the burning floor. Since the powersupply, including the emergency power supply, failed inthe entire building shortly afterwards, the firemen had tocarry all their equipment up the stairs, thus considerablydelaying the commencement of their fire-fighting efforts.Licensed in 1969 and completed in 1972, the building wasonly equipped with sprinklers in a few areas of the under-ground floors. In 1988, the building’s owner decided suc-cessively to install sprinklers throughout the whole build-ing. Only a few floors from the 29th upwards had beenequipped with sprinklers when the fire broke out.Originally dry risers had been converted into wet risers tosupply the sprinklers during the installation work. Twosprinkler pumps were similarly installed, as were pressure-reducing valves on the connections for the wall hydrantsinstalled on all floors. Following the fire, it was found that

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these valves had been wrongly set so that the water pres-sure from the wall hydrants was too low.This also explains why the firemen’s efforts proved unsuc-cessful – the fire on the 21st floor had turned into a conflag-ration in the meantime. Due to the excessively low waterpressure, both the volume of fire-fighting water and therange were inadequate. After four hours, the sprinkler in-staller succeeded in adjusting the pressure-reducingvalves with the aid of special tools so that the requiredwater supply could be guaranteed.In the meantime, the fire had spread to three other floorsand the stairwells were filled with smoke. The fire spreadparticularly along the outer facade. Three firemen died asthey tried to clear the smoke in one of the stairwells bysmashing windows.After roughly 11 hours fighting the fire, the firemen had toretreat from the burning floors because the ceilings threat-ened to collapse. It was therefore decided to fight the firevia the sprinkler system already installed on the 29th floor.The required water pressure was to be obtained by feed-ing water into the risers. Ten sprinkler heads were acti-vated by the heat of the fire and it was finally broughtunder control around 15.00 hours on 24th February.Altogether 19 hours were needed to put the fire out com-pletely. It is assumed that the fire was caused by spon-taneous ignition of oil-soaked rags. In addition to total destruction of the entire furnishings on the floors affected by the fire, the building’s structure and outer facade alsosuffered considerable damage.The owner of the building demanded over US$ 250m in-demnification from the insurers for the repair costs andother losses. In his view, the steel structure of the upperfloors from the 19th floor upwards had been so severelydamaged by the heat that the only alternative was to de-molish and subsequently rebuild the tower. An expert ap-pointed by the courts, however, agreed with the insurersthat the building could be repaired without demolishing it.After protracted negotiations, the claim was settled sixyears after the fire. The building had neither been repairednor was it partly occupied at that time. Barely a year laterit was demolished, probably on account of the significantdeterioration in its condition and on account of its contam-ination with asbestos and PCB (polychlorinated biphenyls).The robust roof and facade construction considerably im-peded the demolition work. The building’s location in thecity centre and adjacent buildings, as well as undergroundrapid-transit railways under the building, prohibited theuse of explosives. The demolition costs were estimated atUS$ 25m over a period of two years.

CONCLUSIONS

These fire catastrophes have once again shown that thethreat posed by fires in high-rise buildings still exists. Although in some cases exceedingly more stringent regu-lations and fire-protection requirements were introducedfor high-rise buildings in many countries throughout theworld in the 1960s and 70s after a series of devastatingfires in various countries with in some cases numerous fatalities (Brazil, Colombia, Venezuela, Korea and others),there are still a large number of older high-rise buildingswhich do not come under the more stringent regulationsor at least not fully – as the fire in Hong Kong proves –since separate statutory rules and regulations are requiredto retrofit structural changes and fire-protection equip-ment in existing buildings.The following list of negative features can be drawn up onthe basis of these fires during the occupancy phase, moreor less representative of numerous similar occurrences inhigh-rise buildings:– absence of fire compartments on large open-floor areas;– vertical spread of fire and smoke through stairwells and

air-conditioning ducts not sealed by fire dampers (chim-ney effect);

– lack of sealing on cable ducts in stairwell walls;– inadequate evacuation of people due to smoke-filled

stairwells;– impeded access to the actual seat of the fire;– absence of a suitably protected firemen’s lift with separ-

ate power supply in high-rise buildings with more than30 floors;

– threat of ceilings collapsing on account of inadequateresistance to fire;

– failure of the emergency power supply since it was notisolated from the shaft of the main power supply;

– no continuous, automatic fire-detection system to giveearly warning of a fire, to signal a fire and to permitrapid location of the fire;

– inadequate instruction and training of security person-nel regarding the action to be taken in the event of analarm and fire;

– lack of standardized procedures between the alarm regulations and the guidelines published by the fire brigade;

– inadequate supply of fire-fighting water due to exces-sively low pressure in the risers, often on account of apartly closed shutoff valve or incorrectly set pressure-reducing valves;

– external attempts to boost the water pressure thwartedby inappropriate marking of the fire connections;

– no automatic fire-fighting systems, such as sprinklers;– failure of the sprinkler systems installed to function

properly.

69 FIRE-DETECTION SYSTEM IN THE MESSETURM IN FRANKFURT

68 SPECIAL COATING ON THE STEEL SKELETON GUARANTEEING ADEQUATE FIRE RESISTANCE

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4.2.4 Fire-protection regulations, loss prevention

The facts and shortcomings outlined in the preceding sec-tion have significantly increased the magnitude of the firelosses described.For this reason, efforts are being made to limit the fire riskwith the aid of corresponding fire-protection regulationsand loss-prevention measures.A high-rise building does not constitute any extra risk withregard to occurrence of the fire, but it certainly does withregard to the spread of fire, smoke and fumes. This is dueto the vertical nature of the building, which greatly pro-motes the spread of fire in the main propagation direction,namely from the bottom upwards.Compared with buildings below the limit for a high-risebuilding – regardless of definition – a high-rise buildingwill always have significant disadvantages when it comesto rescuing people and fighting fires. People cannot berescued from outside the building if they are trapped onfloors out of range of the fire ladders; they can only be lo-cated and rescued via the stairwells. The same applies tofighting the fire, since outside intervention is impossible.The firemen must concentrate on tackling the fire from in-side the building and must make their way to the scene ofthe fire with their equipment through stairwells filled withsmoke and heat.

4.2.4.1 Regulations

Due to these difficulties, the standards and regulations inforce in the majority of countries include special provi-sions for high-rise buildings, with corresponding require-ments to be met in respect of fire prevention and protec-tion. In this way, they take account of the higher risk po-tential.In Germany, for instance, these requirements are laid outin the 1978 “directives”. Besides, compliance with all theprovisions of the Construction Codes in force in each fed-eral state is compulsory.

4.2.4.2 Structural fire protection

Most of these directives relate to the requirements forstructural fire protection, including the rescue routes. The examples described in the preceding section clearlyshow, both in a positive and negative sense, how import-ant it is to meet these requirements.

FIRE-RESISTANT MATERIALS

To ensure the stability of a high-rise building in the eventof a fire, the supporting structure and ceilings must be re-sistant to fire. The characteristic “fire resistant” must bedefined in the applicable standards. However, this meansthat the requirements to be met by fire-resistant parts caneasily differ from one country to the next, depending onthe standards applied. The same holds true for the inspec-tion procedures specified for verification.

The German directives specify a fire-resistance period of90 minutes for the supporting structure in high-rise build-ings and 120 minutes for buildings with a height of morethan 60 m. In both cases, only non-combustible materialsmay be used for the supporting elements.Since high-rise buildings are largely constructed with steelskeletons, unprotected steel cannot be used on account ofits inadequate resistance to fire. Composite structures ofconcrete and steel or fire-resistant coatings or fire-proofpanelling must be used instead.So that the building itself cannot contribute towards thespread of fire, non-combustible materials are largely stipu-lated for the structural parts and elements. Combustible,normally or barely flammable materials are only permittedif structural measures ensure that they cannot contributetowards a fire.

FIRE COMPARTMENTS

As already mentioned, fire can also spread via the outerfacade if windows have been shattered by the heat. It hasbeen found in such cases that the flashover distance of atleast 1 m between two floors as required by the directivesis frequently too short. The alternative possibility of partsprojecting from the facade is similarly not always effect-ive, and it is therefore perfectly appropriate to use fire-resistant glazing.In the cases described above, it was sometimes found thatthe fire had spread over the entire floor and also over sev-eral floors inside the building. Fire compartments with vertical and horizontal structural seals must be created toprevent fire spreading in this way:– The ceilings must be fire resistant and made of non-

combustible materials.– Partition walls must be made of non-combustible ma-

terials and must also be fire resistant for certain uses.– Doorways should at least be sealed with tightly closing,

fire-retardant doors; any other openings required in thewalls must be sealed in an equivalent manner.

– Partition walls in corridors should reach right up to thestructural ceiling.

STAIRWELLS

Stairwells are areas of particular importance, since theymust usually permit safe evacuation of the building in theevent of a fire. Their number depends on the area, heightand shape of the building. Several stairwells are normallyrequired.Stairwells must have fire-resistant walls of non-combust-ible materials. Internal stairwells may only be reached vialobbies sealed by smoke-tight self-closing and at least fire-retardant doors.Smoke vents must be installed at the top of all stairwells;internal stairwells must be equipped with a mechanical,automatically activated ventilation system connected to anemergency power supply. If a fire breaks out, excess pres-sure must be generated in the stairwells to prevent the in-gress of smoke.

4 Risk potential

VENTILATION AND AIR-CONDITIONING SYSTEMS

Ventilation and air-conditioning systems must be installedin such a way that fire or smoke cannot be transmitted tostairwells and other floors or fire compartments. Thecases outlined above clearly show how difficult it is tomeet this requirement. Stairwells, lobbies, safety locks andelevator lobbies must be equipped with ventilationsystems which are isolated from other systems.As a rule, several floors are normally combined into onearea for the ventilation and air-conditioning systems. Toprevent fire and smoke being transmitted via the ventila-tion ducts, fire dampers must be installed in the fresh airand exhaust air ducts on each floor; these fire dampersmust be activated automatically by smoke detectors aswell as manually.More stringent requirements must be imposed on thestairwells in taller buildings (safety stairwells). In particu-lar, the safety locks outside the stairwells must beequipped with mechanical ventilation systems.

SHAFTS AND ELEVATORS

To prevent fire and smoke spreading vertically inside abuilding, the continuous installation shafts for ventilation,electric power, telecommunications, sanitation and docu-ment conveyors must be of the same fire-resistant designas the stairwells. Cable ducts should be sealed with fire-resistant elements on every floor. Openings must besealed with fire-resistant doors or flaps. Automatically ac-tivated smoke and heat vents must be installed here too.Waste-disposal chutes must be protected in the same way.Elevator shafts must also be enclosed by fire-resistantwalls; access to the elevators must be restricted to the cor-ridors or enclosed lobbies. Elevators should be connectedto the standby power supply so that they can automatical-ly be lowered to the ground floor following a power failureor fire alarm.Firemen’s lifts must be installed so that the firemen can arrive at the scene of a fire without delay; this is alreadyspecified by public authorities in certain standards and directives. The time lost in fighting a fire due to the ab-sence of such firemen’s lifts has already been shown bythe cases described above.According to the German directives governing high-riseconstruction, a firemen’s lift is required for all buildingsover 30 m high. Additional firemen’s lifts may be specifiedfor buildings over 100 m high.Every firemen’s lift must be located in a separate fire-resistant elevator shaft. The associated equipment roomsmust likewise be of fire-resistant design and sealed by fire-resistant elements. In many cases, these lifts are addition-ally equipped with rescue materials and radio equipment.Lobbies with fire-resistant walls and at least fire-retardantdoors must be provided at the stopping points for thefiremen’s lifts. A mechanical ventilation system must alsobe provided. The required electrical switchgear and supplylines must be physically separated from other systemsand lines. It is also important to ensure that the firemen’slifts are connected to the standby power supply specifiedfor the building or that they can be operated via perman-ently charged batteries.

4.2.4.3 Active loss-prevention measures

STANDBY POWER SUPPLY

Standby or emergency power supplies must be installedin high-rise buildings from a specified height onwards.These power supplies operate independently of the publicgrid; following a power failure in the public grid, they auto-matically switch on to supply electric power to all safetyequipment:– fire-detection and gas-alert systems; – fire pumps and their control systems;– firemen’s lifts and passenger elevators;– ventilation systems, as well as smoke and heat vents;– fire-resistant sealings of openings; – emergency lighting for rescue routes;– electroacoustic alarm systems and/or paging systems.The equipment providing the standby power supply mustbe isolated from the general power supply and protectedby fire-resistant materials.

FIRE DETECTORS

The importance of rapid and reliable detection and report-ing of fires has already been highlighted in the precedingsection. In larger high-rise buildings, it is therefore essen-tial to install an area-wide automatic fire-detection systemwhich triggers a fire alert on the building’s central controlpanel. This central control panel should preferably be lo-cated on the ground floor or in a permanently manned se-curity centre. Automatic or manual signalling of an alarmto the local fire brigade – preferably via a direct line – de-pends on the conditions prevailing on site. The securityand maintenance personnel must have clear and preciserules of conduct; they must also be fully familiar withthese rules so that human error can largely be excluded.Automatic fire-detection systems should be installed in ad-dition to the existing sprinkler systems, since the latter’sfire-detection sensors are only tripped much later – by theheat of a fire – and trigger an alarm when the sprinklernozzles open.The type of smoke or heat detector to be used must be determined according to suitability in each individual in-stance. Manual detectors – e.g. push-button fire detectors– must be installed in addition to automatic detectors sothat fires can also be signalled by the people present.These detectors should preferably be located in a prom-inent position in the corridors and rescue routes, as wellas in the lobbies to stairwells.The installation of automatic fire or smoke detectors isproblematical due to the presence of ventilation and air-conditioning systems in high-rise buildings and the asso-ciated air streams. Appropriate specialist companies areconsequently considering the use of highly sensitivesmoke detectors (HSSD) and very early smoke detectionapparatus (VESDA). With such apparatus, detection of thesmoke at a very early stage in the fire could be used to activate the fire dampers and then to switch off the air-conditioning.

70 ATRIUM IN A BANK BUILDING

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4.2.4.4 Fire fighting

FIRE EXTINGUISHERS

Hand-operated fire extinguishers must be installed atclearly marked and generally accessible points in high-risebuildings in order to fight incipient fires. These extinguish-ers are intended for use by the building’s residents. How-ever, teams should be present on every floor made up ofthe people who work and live there; they must then be in-structed on what to do if a fire breaks out and also be fa-miliarized with the use of these hand-operated fire extin-guishers.

FIRE-FIGHTING WATER

The cases outlined above have shown how important it isto have an effective supply of fire-fighting water whencombatting a fire in a high-rise building. So that the fire-men can start to fight the fire as soon as they arrive on thescene, wet risers must be installed in every stairwell or intheir vicinity and a wall hydrant with hose line connectedto these risers on every floor. The hoses must be suffi-ciently long to direct fire-fighting water to every point onthat floor. An adequately dimensioned water line and ade-quate water pressure must be ensured when planning anddesigning the building. In very high buildings, boostersystems must be installed in the wet risers to increase thewater pressure.Whether the water for fire fighting can be taken from thepublic mains or from separate water reservoirs or tanksmust be decided in each individual instance in accordancewith local conditions and regulations.For greater safety, it may be useful to install not only wetrisers, but also dry risers into which the fire brigade canfeed water at the required pressure from the ground floor.

SPRINKLERS

An automatic sprinkler system is the most effective pro-tective measure for fighting and controlling a fire in a high-rise building. Care must be taken to ensure that the com-plete building is protected by such sprinklers. In the casesoutlined above, there were either no sprinklers at all or noactivated sprinklers on the burning floors. In the case of“One Meridian Plaza”, the fire was subsequently broughtunder control with the aid of the sprinkler system and anadditional supply of fire-fighting water.Based on past experience, the installation of sprinklersystems is in many countries prescribed by law for high-rise buildings from a certain height onwards – as from60 m in Germany, for example. In some cases, the statu-tory regulations even stipulate that sprinklers have to beinstalled retroactively in high-rise buildings erected be-fore the regulations came into force.Automatic sprinkler systems throughout the building areimportant since they must fight a fire as early as possibleand must either extinguish the fire directly or keep itunder control until the fire brigade arrives to finish off thejob. However, a sprinkler system will normally be unable

to control a fire in full flame, for instance if it leaps from afloor with no sprinklers to one with sprinklers. Sprinklersystems are simply not dimensioned to cope with such developments.Sprinkler systems must meet the following requirements:– they must rapidly control a fire in the fire compartment

in which it breaks out;– they must limit the emission and spread of flames, hot

fumes and smoke;– they must trigger an alarm in the building, preferably

also indicating to the central control panel where theseat of the fire is located;

– the alert must be forwarded to the fire brigade or otherauxiliary forces.

The ability of the system to indicate to the central controlpanel where the seat of the fire is located presupposesthat a separate sprinkler system with an alarm valve is assigned to each floor and to each fire compartment. Asalready mentioned in connection with fire-detectionsystems, the installation of an automatic fire-detectionsystem in addition to the sprinkler system is advisable sothat fires can be discovered and signalled more quickly.Sprinkler systems must be installed in accordance with theapplicable directives or standards, the best known ofwhich include NFPA, CEA, FOC and VdS. All the compon-ents used for installation must comply with the relevantstandards.The various directives and standards permit a variety ofsolutions with regard to the water supply:– water supply from the public mains – possibly via an

intermediate tank on the ground – via booster pumps onthe ground to supply several groups of floors with dif-ferent pressure levels

– intermediate tanks on various upper floors, under eithernormal pressure or excess pressure, to supply thesprinkler groups above or below

– deep tanks and pressurized tanks on the roof, as well asintermediate tanks in the middle of the building, to sup-ply the sprinklers below with static or high pressure

Tanks on upper floors can be replenished via low-capacitypumps. Depending on the type of supply selected, it maybe necessary to install pressure-reducing valves on the in-dividual floors.For a sprinkler system to operate smoothly, it must notonly be correctly installed and set, but also be regularly inspected and serviced by specialist personnel.

OTHER FIRE-FIGHTING EQUIPMENT

Other automatic fire-fighting equipment may be appropri-ate for certain systems in a high-rise building, such astransformers, electrical switchgear and control rooms,computer centres and telephone switchboards. Dependingon the systems concerned, CO2 or – if still permitted bylaw – halon fire extinguishers are two possibilities worthmentioning here, as well as extinguishing systems basedon inert gases.

4 Risk potential

4.2.4.5 Organizational measures

As already mentioned, emergency and alarm plans mustbe drawn up in consultation with the relevant authoritiesand auxiliary forces, especially the local fire brigade. Sothat all fire-protection facilities are fully functional whenrequired, they must be regularly inspected and serviced.The test and maintenance intervals applicable to the differ-ent facilities and systems must be scrupulously observed.It is also important to ensure that the maintenance and security personnel know what procedures to adopt in theevent of an alarm or fire, reinforced by recurrent staff fireand safety training at regular intervals. The catastrophicconsequences due to taking the wrong action have alreadybeen outlined in Section 4.2.4.

4.2.4.6 Atriums

The situation described in Section 4.2.2 with regard to at-riums also poses an additional risk for people during thebuilding’s occupancy as a hotel or department store, forexample. Atriums in particular have a magnetic effect anda concentration of visitors and customers is consequentlyto be found in these areas.A number of special requirements must be met in order toensure personal protection.The required rescue routes must not be directly linked tothe atrium. Instead, they must lead away from the atrium,towards the outside walls of the building. This conse-quently means that the stairwells should be located alongthe outside walls to keep them clear of smoke and to per-mit more effective illumination in the event of a powerfailure.Flashover from one floor to the next must be prevented inthe atrium area. This can be achieved, for example, by in-stalling fire-resistant glazing. The supporting elementsmust also be at least fire-retardant to prevent the top ofthe atrium crashing down onto the inner area.Care must also be taken to ensure that smoke is adequate-ly discharged in the event of a fire. This is particularly diffi-cult on account of the large volume and resultant dilutionand mixing of the smoke. Frequently, discharging thesmoke via a smoke and heat vent will suffice; in criticalcases, however, an additional mechanical means of dis-charging the smoke must also be installed.

4.3 Windstorm

Each of the two twin towers of New York’s World TradeCenter, which will be discussed in more detail in the fol-lowing sections, has a base area of roughly 4,200 m2. Thatis roughly equal to a square base measuring 65 m � 65 m.The towers are 417 m and 415 m high, respectively. Using the highly simplified wind load permitted by Ger-man standards, this yields a total static load of roughly4,500 tonnes per tower from dynamic pressure and windsuction.These values do not, however, include the conditions prevailing locally which must be taken into account whendesigning a high-rise building. The building’s surround-

ings, for example, have an immensely important effect onthe active wind and flow conditions. The location of thebuilding – on open ground or surrounded by other high-rise buildings – has a massive influence on the wind pro-file. The effect of wind separating off the edges of neigh-bouring buildings, reduced wind velocities due to obs-tacles at ground level and effects similar to friction or de-flection of the wind loads due to neighbouring buildingscannot be taken into account in the standard loads.Local wind effects have repeatedly been observed in thecanyons formed by skyscrapers in large cities. One sucheffect is known as the “spinning effect”, a tornado-like effect near ground level which affects pedestrians. In by-gone days, the strong upwinds encountered on the Flat-iron Building in New York used to cause not a few ladiesconsiderable problems as they strolled past. It is alsoknown as the Marilyn Monroe effect in construction aero-dynamics.The shape of the building is another factor influencing thewind forces actually at work. When wind meets an obs-tacle, it normally generates compressive forces on thewindward side of the building and suction forces on theleeward side. In addition, air streaming around the build-ing produces suction forces on the sides parallel to thewind direction. The shape of the corners and edges of thebuilding is particularly important. Separation effects cancause suction and compressive forces several times great-er than the original dynamic pressure. The magnitude ofthese edge and corner forces depends primarily on thegeometry of the building round which the air flows. Basic-ally, it may be said that the more sharp-edged and irregu-lar the building is, the more irregularly the wind forceswill be distributed.Suction forces cause major problems around the roof inparticular. If the roof structure has not been adequately an-chored, parts of the roof may be lifted off and catapultedaway unhindered. In addition to the roof, such elements aslight-metal facades, antennas, promotional signs andwater tanks are some of the parts most seriously threat-ened by wind on high-rise buildings. The risk of partsbeing blown away and flying around is greatest during theconstruction phase. Such parts can cause considerableproperty damage to their surroundings, and harbour potential for bodily injury which cannot be neglected.During the autumn gales in 1972, for example, severalhundred glass elements worked themselves loose fromthe outer facade of the John Hancock Tower in Boston andcrashed down onto the pavement. An area of 50,000 m2

had be reglazed. Facades and roofs are also exposed todriving rain and hail. “Updraughts”, which cause the rainto move upwards instead of down as a result of differentinner and outer pressures, can cause moisture to penetrateinside the building. No fewer than 5,000 panes had to bereplaced for this reason on the UN Secretariat Building inNew York in 1952.A purely structural consideration of the wind will not suf-fice in the case of larger building structures. Wind is aphenomenon which varies strongly in strength and direc-tion and can produce dynamic effects in combination withvortices separating off from the buildings around which

71 DYNAMIC-PRESSURE APPROACHES: effects from friction impact wind speed

72 TYPHOON TRACKS FOR JAPAN AND CALIFORNIA

Wind loadW (kN/m)

Height h (m)

Horizontal load H = W x H

Bending moment M = W x h2

2

73 REPRESENTATION OF WIND IMPACT ON A BUILDING’S GROUND-BEARING PRESSURE

WindCore to stiffenthe building

Foundation

Ground-bearing pressure from vertical load

Ground-bearing pressure from wind

Total

(Ground-bearing pressure from vertical load and wind)

4 Risk potential

the air flows. Particularly in the case of slim buildings cap-able of vibration, such as towers, smokestacks and sky-scrapers, this can lead to stresses which must not be neglected. These vibrations are particularly critical whenthe wind excites the building to vibrate at its resonant fre-quency, thus producing the resonant effects already men-tioned in Section 3.1.3. In response to these fluctuations inthe wind, the building begins to vibrate and can continueto do so until the vibrations reach an amplitude threaten-ing the building with collapse.There are also other, less spectacular problems to besolved by the planners. Depending on their frequency andamplitude, vibrations will be perceived by the building’susers. These vibrations can become unpleasant or even in-tolerable when they reach a certain limit which, however,is normally still far away from threatening the stability ofthe building. In the 1970s, for instance, this resulted in oneof the greatest “building losses” anywhere in the world:due to wind vibration, almost all the tenants moved out ofa high-rise building as if in panic, resulting in a loss ofroughly US$ 75m in lost rent.Such dynamic effects can be counteracted by changingthe rigidity of the building or by installing active or pas-sive damper systems. Passive dampers include baffleplates, for example, to reduce vortex formation. Activesystems can be made up of water tanks, movable weightsor rotating unbalanced flywheels.Shortly after completion of the John Hancock Tower inBoston in the early seventies, it was found that galescaused enormous vibrations in the tip of the tower. Adamping system comprising a 600-tonne counterweightwhich can be moved around as required in accordancewith the wind direction had to be installed on the 58thfloor. It was discovered that the building could have top-pled over at any time. To everyone’s surprise, however, itwould have fallen onto its narrow side, rather like a bookfalling onto its spine.Damping systems are always based on a similar principle.A large mass is moved by hydraulic computer-controlledequipment or pendulum constructions in the direction op-posite to the actual direction of vibration by the building.The vibration energy of the wind is absorbed in this way.The amplitudes and horizontal acceleration forces are re-duced considerably, thus also largely eliminating the effectof dynamic forces.It can be extremely complicated to take wind loads into ac-count in calculations, and it is therefore almost standardpractice today to test the response of a high-rise buildingin the wind tunnel first. As already mentioned in Section3.1.3, even computer simulations cannot always provide asatisfactory answer to the problem. Over the years, thishas given rise to a separate engineering discipline – modelanalysis – to solve the structural and dynamic problems ofa building on the basis of miniaturized models.The widespread belief that it is sufficient to divide all theparameters of the original by the same factor in order toobtain an adequate model is unfortunately not correct.Complex mathematical problems are frequently encoun-tered when drawing up models and it has taken a longtime for model-making to become a precise science.

The main problem for the planning engineers are not thehorizontal loads but the much more complicated questionof transmitting the bending moment due to these loads. Inthe case of a uniformly applied area load, for example, thehorizontal load acting inside the building will represent alinear function over the height of the building, while thebending moment increases quadratically in proportion tothe building height. This means that the bending momentincreases much more strongly than the horizontal loadwith every additional metre in height. More and more so-phisticated solutions must be found for these loads to becontrolled by the supporting structure of a skyscraper.Supporting structures of the type developed in particularby the architects Skidmore, Owings & Merrill (SOM), suchas the “tube” (e.g. World Trade Center, New York), the“bundled tube” (e.g. Sears Tower, Chicago) or the “trusstube” (e.g. John Hancock Center, Chicago), have been pro-duced as a result of the problem that conventional sup-porting structures are no longer in a position to transmitthe wind loads safely (see Section 3.2.2.1).In the subsoil, the bending moments caused by wind mustbe absorbed by soil pressures which can lead to consider-able pressure on the leeward side of the foundations.So far, we have only considered “normal windstormloads“. If we consider, however, that many of the metro-politan centres with skylines dotted with skyscrapers arelocated in areas exposed to severe windstorms – HongKong and Tokyo, for instance, are located in the track of typhoons and even New York can suffer a hurricane, whileChicago is exposed to tornadoes – then it becomes clearthat the planning engineers must also consider this prob-lem. The high wind speeds associated with typhoons, hur-ricanes and tornadoes are not the only problem: a tor-nado, for instance, can cause a sudden pressure drop ofup to 10% of the atmospheric pressure within only a fewseconds, with the result that the outer skin of “airtight”buildings literally bursts – and that applies particularly tothe windows.Compared with the simplified wind load assumed in ac-cordance with German standards, this would lead to anactual assumed wind load of around 10,000 to 13,000tonnes for New York’s World Trade Center if we were totake into account all the effects mentioned in this section.

PRECAUTIONS DURING CONSTRUCTION

The loss potential during construction is an aspect whichcannot be neglected.Although the stability of the building during the variousconstruction phases is documented by correspondingstructural analyses, such equipment items as facade elements or temporary structures are usually not takeninto account, or only inadequately.Additional precautions must therefore be taken during theconstruction work, particularly if the contractor is givensufficient advance warning of an impending windstorm.A loss of more than DM 5m was incurred during construc-tion of a 90-storey high-rise building in the Far East. Sub-contractors had temporarily stored such electrical installa-tion material as control cabinets and relays on the upperfloors of the building shell, but delivery bottlenecks led to

4 Risk potential

a delay in assembly of the facade elements on thesefloors. A considerable proportion of the electrical materialstored on these floors was soaked by Typhoon Herb as itpassed over in 1996 and consequently exposed to the riskof corrosion. Since the damage was foreseeable and pre-cautionary measures were not taken, the insurer was onlyobliged to indemnify part of the loss under the policy.

4.4 Earthquakes

The Richter scale is a logarithmic scale for determining theenergy dissipated in an earthquake. This means that anearthquake measuring 7 on the Richter scale dissipates 32 times the energy of a size-6 quake, while one measur-ing 8 dissipates roughly 1,000 times as much energy.The energy dissipated by these earthquakes is expressedin horizontal and vertical acceleration forces acting on theskyscrapers. The immense forces transmitted from under-ground must be absorbed by the supporting structures ofthe buildings. These dynamic loads are replaced by struc-tural equivalent loads in horizontal and vertical directionwhen a structural analysis of the building is performed.The highest acceleration forces measured to date in anearthquake were recorded during the Northridge earth-quake in Los Angeles (17th January 1994) and amountedto 2.3 times the acceleration due to gravity “g” (g = 9.81 m/s2) in horizontal direction and 1.7 times the accel-eration due to gravity in vertical direction. In simplifiedterms, this means that the planning engineers would add-itionally have to apply roughly 2.3 times the dead weightin horizontal direction and roughly 1.7 times the deadweight in vertical direction to the building when dimen-sioning the supporting structure so that these earthquakeforces can safely be absorbed. Such values are fortunatelyexceptional. Moreover, they only act on the supportingstructure very briefly and are subject to rapid changesof direction. The values assumed in the majority of stand-ards correspond to between 5% and 10% of the acceler-ation due to gravity. Assumed loads of up to 0.4 g are re-quired in extreme cases and US standards already includemore recent earthquake zones in which even higher valuesmust be assumed in certain frequency ranges. In spite ofthis, however, experts still doubt the adequacy of these assumed loads under certain conditions.

HOW DO SEISMIC LOADS ACT ON A BUILDING?

The horizontal and vertical acceleration of the subsoil dueto an earthquake causes the building to vibrate.In simplified form, these loads can be represented by hori-zontal and vertical equivalent loads acting on the masscentre of gravity of the building. The magnitude of theseequivalent loads depends directly on the mass of thebuilding. This leads to the conclusion that as the height ofthe building increases, the mass centre of gravity normallywanders upwards and the flexural effect on the building isintensified by the longer lever arm.The potential earthquake damage suffered by high-rise

buildings varies. The damage depends more on the rate ofmotion and magnitude of the displacement than on the acceleration. The most important and most serious effectsare outlined below, together with the possible protectivemeasures.

SUBSOIL

Natural rock is the best subsoil from the point of view ofits earthquake properties. Sandy soils saturated with waterand artificially backfilled land are considered to be particu-larly critical. The widely-feared liquefaction effects (plasti-cization of the soil) can occur if an earthquake coincideswith high groundwater levels. The building may subse-quently remain at a slant or both the building and the sur-rounding terrain may subside. The importance of the sub-soil was revealed in particular by the earthquake in Mexicoin 1985. The epicentre of the earthquake was located nearthe Pacific coast, at Lázaro Cárdenas. The intensity of theearthquake decreased rapidly as the distance from the epi-centre increased, but then rose strongly (up to 3 points onthe modified Mercalli scale) in Mexico City, some 350 kmfrom the epicentre. The main reason for this increase layin the fact that Mexico City is built on the soft sediment ofa dried-up lake, a subsoil that massively reinforces the effect of the incoming seismic waves through resonant vibration.

FOUNDATIONS

Deep foundations generally display better seismic resis-tance than shallow foundations. Floating foundations canprove advantageous on soft ground, since they may bebetter able to attenuate resonance action. The risk of sub-sidence is considerably greater with floating foundationsthan with deep foundations.“Base isolation” is an anti-seismic construction techniquethat uses the principle of attenuation to reduce vibrations.The building is isolated from the solid subsoil by dampingelements arranged on a foundation ring or foundationplate. Another version was employed for the Court of Ap-peals in San Francisco: the building was retroactivelymore or less mounted on ball bearings which are intendedto gently damp down the impact of a future earthquake.The requirements to be met by all the various anti-seismicbearings are set out, for example, in the Uniform BuildingCode (Division III, 1991).When using these methods, it is important to ensure thatthe damping system is correctly attuned to the applied frequency spectrum and to the resonant frequency of thebuilding. Resonance action can be avoided in this way.As in the case of wind loads, earthquakes can also giverise to resonant vibration. These are described in more detail in Section 4.3. The resonant frequency and conse-quently also the resonance effects can be influenced withthe aid of damping systems. In addition to the isolationsystems for foundations mentioned above, vibrations canalso be damped by using heavy moving counterweights.“Soft” skeleton structures have a period of fundamentalnatural oscillations equal to roughly one-tenth of the num-ber of floors in seconds. The period of a 15-storey buildingconsequently equals roughly 1.5 seconds. Higher edifices

74 IMPACT OF EARTHQUAKE LOADS ON THE CENTRE OF GRAVITY

75 50 T AND/OR 90 T HEAVY DAMPERS TO BE INSTALLED IN TWO JAPANESE HIGH-RISE BUILDINGS TO REDUCE RESONANCE VIBRATIONS CAUSED BY EARTHQUAKES

HIGH-RISE BUILDING

Static equivalent system

V = ay x g

H = aH x g

Horizontal (aH)+

Vertical (aV)

acceleration

H = horizontal equivalent load

which acts on the mass centre

of gravity

V = vertical equivalent load

which acts on the mass centre

of gravity

h = building’s own weight

Mass centre of gravity

76 EFFECTIVE ARRANGEMENT OF DAMPERS IN HIGH-RISE BUILDINGS

4 Risk potential

require a certain time before they oscillate at maximumamplitude. This excitation period lies between 20 and 30 seconds. Enduring earthquakes, such as that in MexicoCity in 1985 (around 3 minutes), consequently represent aparticularly high risk. A so-called whiplash effect was ob-served in the high-rise buildings in Mexico City, for ex-ample, as the buildings abruptly moved back from theirmaximum deflection. Extremely high acceleration forcesand consequently high horizontal forces were involvedhere and resulted in damage to the upper floors, includingsuch superstructures as tanks and antennas.

HEIGHT OF THE BUILDING

Tall buildings are more susceptible to damage from strongremote earthquakes than from weak earthquakes close athand. They normally have a lower resonant frequency anda lower attenuation than low buildings. Short-wave oscilla-tion components in earthquakes are rapidly damped, whilethe long-wave components (frequency f <1 Hz) can stillmake themselves felt at a distance of several hundred kilo-metres, particularly in the form of surface waves.

SUPPORTING STRUCTURE

A distinction can generally be made between rigid andelastic supporting systems. Rigid systems, such as solidwall and ceiling elements, are difficult to deform andtransmit the seismic loads through their rigidity. Due tothe stiffness and lack of ductility in the supporting struc-ture, however, shear cracks can develop in the building.The problem is that more and more energy must be ab-sorbed through the high rigidity and that more and morematerial is required for this purpose.Elastic supporting structures, such as reinforced concreteor steel frames, are highly deformable and absorb the ap-plied seismic energy in this way. The nodes connectingthe horizontal and vertical elements of the supportingstructure are highly stressed, however, and peak loadsoccur both here and on the reinforcing elements (bonds)which must be taken into account when producing theseconnections. However, integrated non-supporting partitionwalls may suffer excessive stresses and break out on ac-count of the major deformation of the frame structure.Skyscrapers with steel frames were hitherto considered tobe particularly resistant to earthquakes, but the Northridgeearthquake in January 1994 brought new insights. In anunexpectedly large part of the flexurally rigid steel framestructures, cracks were found in the welds in the corners ofthe frames. Comprehensive studies were undertaken to de-termine the causes and lay down rehabilitation measures.This strong earthquake also showed that steel supportingstructures do not immediately come crashing down whenoverstressed and that plastic supporting reserves are acti-vated first. The ductility and load-bearing capacity of rein-forced concrete frames, however, can be improved by in-creasing the percentage of reinforcement. When over-stressed, the concrete will usually fail at the risk of a totalcollapse.A number of systems based on the principle of flexibilityand energy absorption are currently being developed toprotect buildings against seismic activity.

The system of active variable stiffness (AVS) is one suchsystem. With this system, the rigidity of the building isspecifically varied by securing the bonds to the membersof the frame structure by means of a variable connectionwhich is essentially made up of hydraulic cylinders con-trolled via valves. An operating power of 20 W is sufficientfor this purpose.The incoming seismic vibrations are detected by sensorswhich transmit the information to a central computer. Thecomputer determines the required rigidity and opens thevalves at the individual points to increase the building’sflexibility in these areas. This ensures that the vibrationsare optimally damped and overstressing is avoided.

SYMMETRY

Symmetric layouts, rigidity and mass distribution lead to a considerably better seismic response than asymmetriclayouts, rigidity and mass distribution. This is becauseasymmetric buildings are subjected to stronger torsion(twisting) around the vertical axis by horizontal seismicloads.

SHAPE OF THE BUILDING

When parts of different height are permanently connectedto one another as, for example, is often found in high-risebuildings with atriums, then the various structures in the building can be subjected to considerable torsionalstresses by the seismic loads. Buildings of differentheights can also be subjected to a whole series of effectsin an earthquake, such as the jackscrew effect observedin Mexico City in 1985: higher buildings were literallyjammed in between lower buildings, thus extensivelydamaging the floors at the clamping point. In some cases,the buildings simply buckled over at the edge of the loweradjacent buildings. Resonance effects can also causebuildings to oscillate so strongly that they hammer againstone another. Another effect observed in high-rise build-ings is the soft-storey effect: due to lobbies, atriums orglazed shopping passages, some floors – usually near theground floor – are distinctly “softer” than those abovethem. These “soft” floors then collapse in an earthquake.A further source of loss potential relates to the standardsapplied. Many countries do not have their own earthquakestandards and simply adopt the corresponding regulationsfrom others, such as the Uniform Building Codes from theUSA. This means, however, that common local seismic ef-fects are not covered. Moreover, application of the stand-ards is not mandatory in many countries and their super-vision not sufficiently stringent. One of the main problemsthat is repeatedly found in conjunction with earthquakedamage lies in the quality of the work. Poor-quality mater-ials, poor training from the engineers to the workers, cor-ruption and the pressure of time must be mentioned inthis context.“Only fools, liars and charlatans predict earthquakes”, ac-cording to C. F. Richter, the man who gave his name to theRichter scale.New and potentially promising methods are being devel-oped in the meantime, but the question remains whetherthese methods can ever be properly applied in practice.

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Such predictions are naturally of subsidiary importancewhere physical losses are concerned, such as a cata-strophic loss estimated at up to US$ 3bn in the metro-politan district of Tokyo. Where personal protection is con-cerned – and up to 600,000 fatalities are assumed for theaforementioned scenario – such precise earthquake fore-casts would be of inestimable value.

4.5 Foundations, settlement and subsidence

4.5.1 FoundationsParticular attention must be paid to additional foundationmeasures (see Section 3.2.1) when erecting a high-risebuilding and above all if it is to be built on poor or dam-aged subsoil.Foundation structures up to 100 m deep and known as“barrettes”, each comprising four diaphragm wall elem-ents, were required to transmit the loads safely into nat-ural foundation soil under the Petronas Towers in KualaLumpur, Malaysia, which we have already mentionedabove. Load tests should really be performed on such foundation structures before starting the high-rise con-struction work, but they are economically unacceptable

and technically almost impossible on account of the highvertical loads to be applied.Instead, the load-bearing capacity of the deep foundationis determined in addition to routine investigation of thedrilling explorations (assessment of the soil strata encoun-tered). The integrity of the respective pile and diaphragmwalls can be continuously monitored with the aid of suchspecial methods as ultrasound; special pipelines are inte-grated into the foundation structures to permit a certaindegree of rework if defects arise, for instance by means ofsubsequent injection.Although such complex foundation work can only be undertaken by highly specialized and experienced civilengineering contractors, mishaps occur all the time. Whenproducing the trenches for the diaphragm walls, for in-stance, or when drilling holes, particularly at great depth,opened fissures or existing but undetected channels resultin loss of the bentonite supporting slurry, thus jeopardiz-ing the stability of the trench or hole or even causing it tocollapse.The long cages of reinforcing steel can become wedgedagainst the wall of the deep trench or drill hole, making itimpossible to lower them to the required depth. It is notuncommon for the freshly positioned reinforcing cage tobe pulled upwards a short distance when the casing string

77 EARTHQUAKE IN KOBE, JAPAN

78 CORRODED SUPPLY LINES79 TENSION CRACK IN A CROSSLINKED POLYETHYLENE PIPE

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is raised after completing the pile. This can impair the in-tended load-bearing capacity or even make it necessary toabandon the pile in question.The required load-bearing capacity may likewise not beachieved if deviations from the vertical axis exceeding thetheoretically permissible limit occur as a result of encoun-tering obstacles or due to carelessness while drilling (sinking). This is not uncommon, particularly in the case of long piles.Simple repairs or reworking are rarely possible in suchcases. Extensive supplementary measures, such as re-placement piles, pile bents or injections, will usually berequired on account of the simultaneous disturbance pro-duced in the subsoil. These supplementary measures mayprove considerably more expensive than the original foun-dation.In many cases, this will also give rise to the questionwhether a mere defect is involved or whether it is a phys-ical loss with corresponding consequences for indemnifica-tion under the policy. In the latter case, the indemnificationfor such supplementary costs should be suitably limitedby correspondingly worded clauses, limits or other restric-tions when concluding the policy before constructionstarts.

4.5.2 Settlement and subsidence

Settlement and subsidence are another risk. It must bepointed out, however, that a certain degree of settlementwill be unavoidable in all these projects. The equilibriumof forces originally present in the ground is disturbed byexcavation of the soil for the underground floors and byapplication of the structural loads. Depending on the typeof building, the soil conditions and the foundation select-ed, settlement will occur immediately or at a later date.Depending on the method selected (diaphragm wall, borediaphragms), the retaining wall can also cause the groundto settle and result in damage to third-party property. Forthis reason, it is advisable to record prior damage onneighbouring buildings as evidence before starting thework.The planning engineer is responsible for ensuring thatsuch settlement is determined correctly and for orderingappropriate structural precautions so that the settlementremains within tolerable limits. This can be achieved by acorresponding arrangement of joints in the building and

other structural measures, such as the use of hydraulicjacks.Problems only arise, however, if defective work, undetect-ed disturbances, subsequent changes in the subsoil or anincorrect appraisal of the load-bearing capacity lead toabrupt and extensive subsidence which may threaten thestability of the entire building.Such subsidence can occur during the construction phase,when the building has already reached a certain heightand consequently also a certain weight. It may also occurafter several years and may not only cause the building tocollapse, thus resulting in a total loss, but can also resultin devastating casualties.The spectacular collapse of a high-rise building will inmany cases be due to a combination of causes, such as acombination of design errors, inadequate workmanshipand problematical soil conditions.Attention must be devoted to the horizontal forces in par-ticular when designing the foundations for high-rise build-ings on sloping ground.In one case, reject railway tracks were used as the founda-tion element for a high-rise building instead of the usualsteel or reinforced concrete piles. Although the trackswere welded together to give them the requisite load-bearing capacity, they still did not conform to the ap-plicable regulations. When heavy rainfall subsequentlycaused a landslide on a nearby slope, these piles wereneither structurally nor theoretically in a position to ab-sorb the additional active horizontal earth pressure. Thepiles buckled and some sheared off, with the result thatthe high-rise apartment block literally tipped over andthen collapsed.It is very difficult to repair a high-rise building when itsstability has been jeopardized by such severe subsidence.The defective foundations can be reinforced with the aidof injections, supplementary piles or root piles if neces-sary on account of the limited height available on theunderground floors. However, such measures are almostimpossible in a completed high-rise building, due to itsimmense overall weight, and the only alternative is usual-ly to demolish the building.Even when high-rise buildings are still under construction,i.e. in a phase where repairs would still be possible onaccount of the lower dead weight, demolition of the shellwill usually prove to be the more economical, time-savingand generally better alternative for the principal.

4.6 Water

GENERAL

Like other buildings, high-rise buildings can also sufferdamage due to water. As a rule, this damage will be dueto soaking, soiling, discoloration, corrosion, shrinkage orexpansion and mould.

DEVELOPMENT OF LOSSES

The damage is due to the interplay between the nature ofthe media concerned (e.g. drinking water, heating water,effluent), the quality of the installation materials, designand execution of the plants and the prevailing operatingconditions.In the case of high-rise buildings, the risk is further aggra-vated by the fact that leaking water rapidly finds its way tofloors below the actual leakage point, with the result thatseveral floors may be affected, depending on the durationof the leak and the amount of water involved.The considerably larger size of the installations in compari-son to “normal” buildings is another risk factor: boostersystems and pumps, pressure reducers, etc., are all need-ed in order to distribute or discharge the drinking water,heating water and effluent horizontally and vertically, thusincreasing the number of possible leaks.

4.7 Special structural measures

Considerations on the conversion, rehabilitation and final-ly demolition of high-rise buildings have been subsumedunder this heading.

4.7.1 Conversions

Conversions are constantly being made to any high-risebuilding with thousands of square metres of useful floorspace. Redecoration and modernization are the common-est conversions, in addition to those necessitated bychanges in operational procedures and use of the build-ing.More stringent or additional requirements in respect offire protection, installations or computer systems can alsomake conversions necessary.On the one hand, conversions and changes of use are fa-cilitated by the separation of shell (= supporting structure),installations and interior finishing commonly applied inthe construction of modern high-rise buildings; at thesame time, however, it is precisely this separation that im-poses limits on what is economically acceptable. Even iftechnically feasible, conversions involving changes to theexisting structural system, i.e. to the supporting structures,will usually be rendered impossible on account of thecosts involved. For this reason, conversions will almost al-ways only affect the interior finishing and the installations.The range of possible conversions extends from simplyrelocating interior wall elements or fitting complete newfalse ceilings or laying new floor coverings to “gutting”the building completely. In such a case, all or part of the

building is restored to the condition of a shell and then refinished with corresponding installations and interior finishing in line with its new use.However, if these conversions result in considerably higher loads for the building, these loads will have to bedischarged via extended foundations in extreme cases.Particular attention will have to be paid to settlement inthis context. The problem can be minimized by providingadditional piles, for example. From a technical point ofview, however, this will prove fairly difficult as the workingheight of the drills is usually limited by the height of thevarious levels in the underground car parking.The fact that conversions are often undertaken while oper-ation continues without interruption in those parts of thebuilding and on those floors not affected by the work notonly makes the work more difficult, but also increases therisk for the insurer. The nuisance due to noise and un-pleasant odours or temporary failure of the sanitary instal-lations, heating or ventilation are relatively harmless phe-nomena. The dust inevitably generated by such conver-sions, on the other hand, can have serious consequencesif high standards of purity and hygiene must be met bythose areas still in operation, such as computer systems ordoctors’ offices.As in the case of “normal” building work, the use of suchflammable substances as adhesive and bituminous mater-ials or naked lights, for instance for soldering and welding,will be unavoidable when carrying out conversions. Ex-tremely stringent requirements must therefore be imposedon the fire-protection measures due to the incomparablygreater risk potential. In particular cases, the fire brigadewill have to be ready on site to take immediate action if anemergency arises.Another problem associated with conversions is that thenormally strict controls with regard to access and author-ization are often suspended for the conversions: workers,suppliers and the vehicles transporting materials andequipment need “open doors”. This naturally also in-creases the risk of unauthorized persons exploiting thesituation and simply marching into the building.Conclusion: all conversions, no matter how slight, must bethoroughly planned in advance and organized in detailwith due consideration given to all eventualities.

4.7.2 Rehabilitation

Rehabilitation is an extreme form of conversion. The twocommonest reasons making rehabilitation measures ne-cessary are– physiologically harmful materials, such as materials

containing asbestos or materials with excessive formal-dehyde concentrations, or

– potentially dangerous structures.

All the aspects already mentioned in the previous sectionalso apply here in particular. In addition, there is the prob-lem of disposing of the physiologically harmful materials.Correct disposal of contaminated materials and sub-stances not only poses a technical challenge, but is alsoone of the most difficult jobs for third-party liability insur-

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ers on account of the possible environmental impact andhealth hazard.In the majority of cases, it will be impossible to continuenormal operation of the building while the rehabilitationwork is in progress. For this reason, such rehabilitationwill usually also be associated with conversion and a completely new interior finish.An alternative method was employed when WintertonHouse in London was rehabilitated in the 1960s. All falseceilings and facade linings were removed first. The newbrick facade was then built up on its own foundationsaround the steel supporting structure. The facade wassecured to the supporting structure by means of steelbrackets for reinforcement. An active construction wasrequired to compensate the differences in thermal expan-sion of the facade and supporting structure. In this case,the roof structure links the inner skeleton with the outerwall via hydraulic presses. These presses are in continu-ous duty and maintain a constant compressive strain onthe upper edge of the masonry. The building’s outer andinner columns were reanchored in the roof structure, thusreducing the load in the columns. Ceilings in line withtoday’s state of the art were then installed.

4.7.3 Demolition

Demolition remains the method of last resort when evenchanges in use, conversion and rehabilitation can no long-er meet the more stringent requirements imposed on abuilding.It is no longer standard practice today and in many coun-tries even illegal simply to demolish a building – oftenwith the help of unskilled labourers. Experienced special-ists are needed not only in order to meet environmentalregulations requiring that all materials and parts accumu-lated in the course of the demolition work be carefullysorted, but also to judge how the complex supportingstructures will react during the demolition. Within only afew years, the demolition of a building has ceased to be a low-tech job and become a highly specialized technicaltask.Specialists often take over when the building has finallybeen gutted, i.e. when all interior finishings and installa-tions have been removed and duly disposed of (recycling)and when there are no further physiologically harmfulmaterials in the remaining supporting structure. Either thebuilding is then dismantled carefully and with as littlenoise and dust as possible, the reinforced concrete literallybeing “nibbled away” by special machines, or – if the cir-cumstances permit – explosives experts apply their pre-cisely primed charges to the predetermined points afteranalysing the drawings and inspecting the remainingbuilding. As spectacular explosions of high-rise buildingshave proved, experienced experts can make a buildingcollapse in such a way that the surrounding structuresremain undamaged. Less carefully planned explosions,on the other hand, have caused serious damage to thesurrounding areas.

80 BLASTING OF A HIGH-RISE OFFICE BUILDING

4.8 Other risks

For the sake of completeness, mention must also be madeof a few other risks which, although closely associatedwith high-rise buildings, either occur very rarely, such asterrorism, are unavoidable, such as wear, or are often un-derestimated, such as the consequential costs due to phys-ical damage.

4.8.1 Terrorism

High-rise buildings with their characteristic silhouette in acity’s skyline not only represent a magnet for tenants, customers and guests, but unfortunately also become a popular, sometimes inadvertent, target for terrorist attacks,as the 1998 bombing attacks in Nairobi and Dar es Salaamshow.A skyscraper’s famous name is enough to assure the ter-rorists of the desired media attention following an attack.In many cases, however, the dominant presence of a high-rise building will suffice to obstruct the devastating shockwaves of an explosion somewhere else.

OFFICE TOWER OF COMMERCIAL UNION INSURANCE IN

LONDON

Precisely that was the fate of the office tower of Commer-cial Union in London when a bomb exploded on the even-ing of Friday, 10th April 1992, in the immediate vicinity ofthis newly renovated tower with its completely new facade.The physical damage sustained by the building amountedto more than £40m, plus the loss of rental income duringthe tower’s restoration. Although there is no effective pro-tection against such indirect effects of terrorist attacks, thecrisis management set up by CU for such events passedits first test with flying colours and saved the companyfrom potentially ruinous loss of business.After corresponding reports in the national press andthanks to availability of the complete data in Croydon, thecompany was able to resume its business at 9 a.m. on thefollowing Monday. The problem of such business inter-ruptions will be discussed in the next section.

WORLD TRADE CENTER IN NEW YORK

The consequences of a car-bomb explosion in the under-ground car park of New York’s famous World Trade Centeron 26th February 1993 were even more devastating. Six people were killed in the explosion and more than1,000 were injured; the explosion caused immense physi-cal damage estimated at around US$ 500m. The bomb fortunately exploded around lunchtime when many of theoffices were empty. Around 50,000 people normally workin the skyscraper and over 80,000 visitors are additionallyrecorded every day.Contrary to the recommendations of experts, there wereno special precautions against such terrorist attacks on theWorld Trade Center with its 417-m and 415-m-tall twin towers and the 22-storey Vista Hotel between them. Theemergency power generators and central water supplywere located on the uppermost of the six underground floors immediately above the parking decks and therefore

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In addition to taking into account the existing supportingstructure, it is also important to investigate the effect ofconversions, rehabilitation and demolition work on the ex-isting supporting structure, neighbouring buildings andthe site environment.The most appropriate methods are then selected on thebasis of such influencing factors as– vibrations, – noise, – dust, – site traffic, – contamination. The work is preceded by detailed analyses of the existingstructures.

4.7.4 Disposal

As already mentioned in the preceding section, particularattention must be paid to disposal of the materials accu-mulated in conjunction with conversions, rehabilitationmeasures and demolition jobs. Specific reuse of the ma-terials will be unavoidable as contaminated materials mustbe dumped on special landfills in some regions and land-fill space for construction rubble becomes scarcer and in-creasingly more expensive.The materials must be analysed before starting the workand classified according to their contamination, suitabilityfor disposal and reusability.The primary objective is to reduce the volume of contam-inated rubble so that it can be decontaminated (if possible),for instance by washing the soil. If this is not possible, thematerial must be dumped on special landfills.The degree to which the materials can ultimately be sorteddepends on the local regulations and on the landfill capa-bilities and costs. Separating and sorting the contaminatedmaterials often entails a great deal of work.Such reusable materials as concrete, steel and PVC aresorted, delivered to recycling plants and reprocessed. Inthe case of concrete or masonry, this can also be done onsite using mobile plants. The resultant materials (crushedstone, etc.) can then be used in the construction of a newhigh-rise building, thus also reducing the volume of trafficon site.

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highly vulnerable, as this underground car park was opento all users. Three underground railway lines also havetheir own stations on two of these parking decks.When the bomb concealed in a delivery van detonated, itblasted a hole in the concrete floors of the decks aboveand below and left a crater roughly 30 m deep. Numerousfires broke out on the three levels affected. Caustic smokerapidly spread through service and elevator shafts in thetwo towers and in the hotel.

FEDERAL BUILDING IN OKLAHOMA

The world was even more deeply shocked by the explosi-on of a car bomb outside the Alfred P. Murrah FederalBuilding in Oklahoma City, USA, on the morning of 19th April 1995.The nine-storey office building accommodated not onlyseveral federal authorities, but also a daycare centre foryoung children. The blast killed 168 people and injured475. The bomb with almost two tonnes of explosive hadbeen concealed in a small closed pick-up truck parked nearthe main entrance to the building. The building was posi-tively “lifted” by the shock wave from the detonation andthe supporting structure so severely damaged that almostone-half of every floor collapsed and the glass facade wassheared off. The people inside the building were buriedunder the rubble. Several nearby buildings also sufferedconsiderable damage and numerous cars caught fire. Win-dows shattered even at a distance of several kilometres.Altogether 43 fire brigades and auxiliary organizations,many of them from other federal states, took part in therescue operation which commenced immediately. Manypeople were recovered alive from the rubble. The completeloss was estimated at more than US$ 300m, but the dam-aged building itself was not insured. It had to be complete-ly demolished on account of the major damage suffered.What insights and conclusions can be drawn from theseoccurrences? There is naturally no such thing as completeprotection against the inventiveness and fanatical destruc-tive urge of terrorist attackers. Nevertheless, appropriatesecurity and fire-protection measures should make it moredifficult for them to achieve their objectives.One such measure would be total control of all incomingand outgoing people and vehicles. Thanks to the attentive-ness of the security personnel, for example, it was pos-sible to defuse the bomb placed by a terrorist organizationin a delivery van outside the new office tower on London’sCanary Wharf. If such an attack cannot be prevented, how-ever, it is extremely important that the emergency plansand fire-fighting measures already discussed in the pre-ceding sections be applied and function smoothly.

4.8.2 Impact

The risk of an “impact or crash of a manned flying objector parts thereof or its cargo” which is normally included inthe insurance cover for buildings, is considered a neces-sary but rarely claimed insurance element. The number oflosses of this type reported to date is admittedly small, al-though the media frequently feature such “near misses”.When an accident of this type does occur, however, it is al-

most always a genuine catastrophe, possibly with numer-ous fatalities and enormous losses.Two of the most spectacular cases in which an aircraft col-lided with a high-rise building occurred in New York andnear Amsterdam.

EMPIRE STATE BUILDING, NEW YORK CITY

A light fog lay over the city on the morning of Saturday,28th July 1945. Visibility was no more than 2 miles, the cloud ceiling had dropped to roughly 500 m. Shortlybefore 10 a.m. a B25 bomber of the US Air Force with acrew of three approached Newark airport, New Jersey, justa few miles from the centre of Manhattan. The 12-ton aircraft was scheduled to land at Newark a few minuteslater. At a cruising speed of roughly 320 km/h, the bombercrossed the East River and Manhattan above 42nd Street.Witnesses saw the aircraft heading directly towards ahigh-rise building on Park Avenue at a height of roughly2,000 ft. Pedestrians and shoppers saw how the aircraftjust managed to evade this building at roughly the level ofthe 22nd floor and then avoided colliding with anotherskyscraper on Fifth Avenue. Most of the witnesses subsequently said that it seemed as if the pilot was having technical problems. Whether that was indeed thecase is still unknown today.What is known is that, for whatever reason, the aircraftcould not be pulled up in good time and drilled its wayinto the 78th and 79th floors of the Empire State Buildingat precisely 9.52 a.m. Fire broke out immediately in thebuilding. The bomber’s wings broke off first. The fuselageripped a 6-m hole into the facade and penetrated morethan 25 m into the building. One engine continued rightthrough the 79th floor and emerged through the outer wall on the southern side of the building, from where itdropped onto the roof of a 12-storey building which alsocaught fire. The 800 gallons of kerosene in the tanks ex-ploded and totally destroyed the western half of the twofloors concerned.The other engine made its way through an elevator shaftand ultimately came to rest in a stairwell, blocking this escape route. The suspensions on several elevators weredestroyed and two cabins crashed 300 m to the bottombasement floor. By a miracle, two people in the lifts survived the crash with serious injuries, while 14 peoplewere killed in the offices directly affected by the explosionon the 79th floor. The 78th floor was fortunately only usedas a store and there were no further fatalities there.All in all, the catastrophe could have been even worse.Hundreds of people would probably have been killed inthe offices and on the surrounding streets on a normalworking day. The physical loss totalled around US$ 1m –an immense sum in those days and the equivalent of 4%of the contract price – and it took over a year to repair thebuilding.

81 INTERIOR OF A HIGH-RISE BUILDING FOLLOWING A BOMB ATTACK

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82 Left: WOODEN PANELS ON A GLASS FACADE DESTROYED BY A CAR-BOMB ATTACKTop: INTERIOR VIEW OF ONE FLOOR

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BIJLMERMEER NEAR AMSTERDAM

A Boeing 747-200 F operated by the Israeli airline El Alwith a crew of four and 320 tonnes of freight on boardwas on its way from New York to Tel Aviv via Amsterdamon 4th October 1992. Ten minutes after taking off fromSchipol Airport, the fully laden aircraft had evidently notgained sufficient height and crashed into the two high-risebuildings “Groenevenen” and “Kruitberg” in a modernsatellite town near Amsterdam. Both buildings caught firewithin seconds of the crash as a result of the full tanks. According to official figures, 43 people were killed in add-ition to the crew; 233 flats were destroyed. Insiders as-sume, however, that many more people were actuallykilled, since these flats were inhabited by numerous immi-grants and asylum seekers, and not all residents may havebeen officially registered.Not long before the accident, experts at Schipol airporthad considered the risk of an aircraft crashing into thisresidential area to be “negligible” – a disastrously false assessment, as it turned out.Despite adequate lighting, inclusion in flight maps anddesignation of air corridors with sufficient distance, high-rise buildings will always constitute a certain impact risk ifonly on account of their height.

4.8.3 Collapse

The collapse of a building could be considered the “worstcase” for everyone involved in its planning and realization.The financial consequences for its owner and the expos-ure risk for the people inside the building and in its vicinitywhen it collapses are devastating.The possible causes are often complex and difficult to as-certain retrospectively, but risk potential can be identifiedand corresponding precautions taken.The following risks are a potential source of errors duringthe planning and construction phases:– Flawed analysis of the subsoil– Flawed structural analyses– Lack of coordination between the parties involved in the

planning and realization (changes which are not takeninto account, etc.)

– Defective work (stripping times, wrong quality of mater-ials, etc.)

– Incorrect use of the building during the constructionphase (e.g. concentrated storage of materials on floorsnot structurally dimensioned for this purpose)

During the occupancy phase, a building may collapse forthe following reasons:– Structural changes which have not been taken into ac-

count in the structural analysis of the building (e.g. byadding floors or removing supporting structures)

– Poor maintenanceEvacuation of the people in the building depends verystrongly on the manner in which it collapses. No precau-tions can be taken against a sudden failure of the support-ing structure. Cracks in the tension zone of the concrete orplastic deformation of the steel structure could be detect-ed if the building is properly serviced. It would then haveto be closed due to the risk of collapsing.

The leaning tower of Pisa, on the other hand, shows justhow long it can take for an impending collapse actually totake place. Due to poor soil conditions, the tower hasleaned over further and further over the centuries, but ithas still not collapsed.

4.8.4 Wear

A high-rise building is exposed to time-dependent influ-ences during its occupancy period. Ageing processes onsuch building parts as windows, joints and seals are influ-enced in particular by temperature, wind, UV radiation,moisture, dust and gaseous emissions. They play an im-portant part in conjunction with plastics and rubber ma-terials and differ from the corrosion processes primarilyaffecting metallic materials. In the majority of cases, cor-rosion of metallic materials on facades and roofs doesnot constitute any form of wear – assuming that mistakeshave not been made in the planning, execution and choiceof materials – but is instead a desired process covering themetals with a protective layer. Inside the building itself there are numerous installations,machines and units, such as pumps, fans, compressors,elevators and garage doors, the moving parts of which aresubject to wear in accordance with their operating condi-tions.Maintenance schedules (for maintenance, inspection andrepair) must be drawn up and observed in order to minim-ize the probability of losses occurring due to componentwear. Unfortunately, such intentions do not always func-tion as smoothly as with motor vehicles.

4.9 Loss of profit

The risk potential and examples of losses discussed in thepreceding sections have focused above all on the physicaldamage to the building as such, while the considerableconsequential losses following such an occurrence haveonly been mentioned in passing. This problem will now bediscussed in more detail here.

CONSTRUCTION PHASE

As already mentioned, the realization of high-rise con-struction projects requires considerable financial resourcesand investments, for which interest and repayment instal-ments are often already due during the planning phase orat the latest when the land is purchased. The owner’s pri-mary aim will be to ensure that the high-rise building iscompleted as quickly as possible, not only on account ofthe considerable borrowed capital and higher resultantinterest burden, but also in order to make a profit. Everymajor loss during the construction phase will consequent-ly thwart his efforts to achieve this aim and can even jeopardize his financial survival.Particularly in the case of high-rise buildings, the investorwill also seek to conclude a large number of contracts withfuture tenants or lessees during the construction phase.Such contracts usually not only govern the tenancy assuch, but also the approval for often expensive interior fin-ishings tailored specifically to the tenant’s requirements.

83 AIRCRAFT DEBRIS AFTER A PLANE PLOUGHED INTO THE EMPIRE STATE BUILDING

84 AIRCRAFT CRASH ONTO A BLOCK OF FLATS IN AMSTERDAM

85 BOMB ATTACK ON A FEDERAL GOVERNMENT BUILDING IN OKLAHOMA, USA

Delayed completion of the building can therefore alsohave negative effects on the contracts already concluded,as well as on the dates agreed between the tenant on theone hand and tradesmen, suppliers or service-providerson the other. Innumerable other consequential costs arealso possible, the least of which will be media advertise-ments publicizing the forthcoming opening of new prem-ises.Since these are consequential losses, the best precautionis to avoid the physical losses leading to such delays incompletion of the construction work. These statementsthus merely serve to underline the measures already out-lined in the preceding sections with regard to loss preven-tion.The possibility of covering some of these consequentiallosses through corresponding insurance products will bediscussed later.

OPERATING PHASE

The main financing aspects concerning the constructionphase also apply equally to the operating phase. Regard-less of whether own or borrowed capital has been invest-ed, the investor will expect a guaranteed return on his investment. Even as the property is being let, the ownerwill therefore seek to attract solvent tenants guaranteeinga profit in line with his cost calculations within the frame-work of a long-term lease. This is particularly true if theowner has during the construction phase already providedadvance financing for complex interior finishing meetingthe tenant’s wishes.The owner of a high-rise building will therefore wish toknow what impact a maximum foreseeable physical lossdue to the aforementioned risk potential could have on hiscalculated revenues and expenditures:– How long will it take for the property (offices and busi-

ness premises) to be restored and when can they berelet?

– Can the property be relet immediately and generate thecalculated revenues or must rents be expected to de-cline due to the growing supply in the neighbourhoodof the property?

– What is the term of the individually concluded leases?– What revenues are guaranteed by these leases over

their entire term? Under what conditions could a tenantrescind the contract completely or insist on a pro ratareduction in rent due, for example, to a physical loss ofthe aforementioned type?

– What is the maximum term to be foreseen by the ownerof a high-rise building, i.e. from occurrence of the phys-ical loss until the calculated rent revenues are obtainedagain; and what losses will he in all probability have toinclude in his calculations during this period?

Investors and owners are not the only people, however,whose fate largely depends on the profitability of a high-rise building and who must precisely identify, appraiseand control their associated risks before considering awell-conceived insurance.The following risk potential and other aspects must alsobe weighed up by the tenants renting offices and businessspace in what is no doubt an attractively located high-risebuilding from a strategic business point of view:– If the tenants have obtained very favourable long-term

leases in the past which, however, can be terminatedprematurely on account of material physical damage tothe building or to the rented furnishings, these tenantsmust expect to pay considerably more when rentingcomparable business premises if rents have risen sub-stantially in the meantime.

– Quite apart from the additional rent to be paid for tem-porary or definitive removal to alternative premises, thetenants concerned will possibly also have to reckon withconsiderable additional costs for all the special meas-ures required in order (preferably within the scope ofcontingency plans) to avoid or at least minimize anynegative effects on the company’s operating and earn-ings situation. In spite of this, however, it will probablybe impossible to prevent all loss of gross profit betweenoccurrence of the physical loss and restoration of normaloperating conditions.

The economic environment of the high-rise constructionproject must also be taken into account – depending onthe order of magnitude in each instance. It was mentionedin Section 3.4.2.4 that high-rise buildings could be com-pared to a “town under one roof”. The World Trade Center(WTC) in New York (see Section 4.8.1) is an example ofthis economic aspect underlining the loss-of-profit risk. The WTC is made up of seven buildings accommodatingsome 1,200 businesses on an area of 7 hectares. The twooffice towers are 415 and 417 m high, respectively, and arelinked by a 22-storey hotel complex. With 110 floors, theyprovide roughly one million m2 of useful floor space forvarious offices, such as investment companies, brokers,raw commodity markets, customs authorities and televi-sion companies. A 100-m television mast with various antennas is mounted atop one of the towers. The secondtower additionally accommodates a switchboard for NewYork’s telephone system with, among other things, thetelecommunications for air traffic control at New York’sthree largest airports. Underneath the extensive open-airplaza are the largest covered shopping promenade inManhattan, six department stores and shops, 2,000 park-ing spaces, two vehicle tunnels and the stations for threeunderground railway lines carrying the roughly 50,000people working in the two towers and the roughly 80,000visitors recorded every day. Numerous businesses, organ-izations and a complex infrastructure are consequently dependent on the smooth functioning of the two towers.

4 Risk potential

4 Risk potential

The magnitude of the direct losses caused by the carbomb on 23rd February 1993 has already been describedin detail. Both office towers were closed by official orderuntil further notice.Due to the surplus of offices available in New York City in1993, the towers’ owner – the Port Authority Risk Manage-ment – was naturally anxious to do everything possible asquickly as possible in order not to lose tenants. Perfectcontingency plans meant that 220 floors were cleaned upwithin only 21 days and the towers reopened for use as offices on 19th and 26th March, respectively.During this one-month break, the tenants in the towershad to find alternative premises at considerable expenseand had to finance the temporary furnishings. This wasnot always an easy matter in view of the special technicalequipment required in various cases. One Japanese insti-tute quoted lost revenues in the order of US$ 12m per day,while another cited a figure of US$ 20m daily.The absence of the people working in the office towers in-evitably also led to loss of profit for the other businessesand organizations in the area and surrounding districts,particularly the transport corporations and the toll bridgesand tunnels over and under the Hudson River, which sep-arates New York from New Jersey. In this way, an eco-nomic loss of roughly US$ 1bn was incurred in a one-month period.Particularly when assessing the loss of profit risk, it is im-portant always to remember that “if anything can gowrong, it will – at the worst conceivable moment – andeverything always takes longer than expected“.

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55.1 Property insurance 5.3 Problem of maximum loss 5.5 Reinsurance

5.2 Third-party liability insurance 5.4 Underwriting considerations

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GENERAL

The project documents usually only provide informationon the finished building and how it is integrated into thetownscape. Since different methods are often employedfor the construction work, the respective risk potential dur-ing the construction phase must also be weighed up andvalued by the insurer.Almost every blueprint of a high-rise building also in-cludes a series of tailor-made elements, such as facades or special foundations, with divergent risks which consequently can be considered a kind of prototype, at least in part. The effects of such semi-prototypes forcontractors’ all risks insurance must be investigated separately.At the end of the planning phase, if not before, the princi-pal must decide how the risks during the constructionwork are to be spread between himself and the contract-ors. This must already be specified in the tenders. Suchearly and precise demarcation of risk between the princi-pal and the contractors is of great importance, not only fordetermination of the premium, but also for subsequentloss events.

5.1 Property insurance

A distinction must first be made between construction of ahigh-rise building (construction or erection) and the sub-sequent occupancy phase. The first phase will be covered

by contractors’ all risks insurance, possibly including coverfor construction and erection equipment. The secondphase, however, requires a series of policies covering suchrisks as fire, complete or partial collapse (decennial liabil-ity) and various additional perils (natural hazards, waterdamage, glass breakage, etc.).

5.1.1 Contractors’ and erection all risks insurance

Construction work on a high-rise building is normally covered by contractors’ all risks (CAR) insurance. If cover-age in accordance with an erection all risks (EAR) policy is required in certain cases for the interior finishing, in-cluding installations for air-conditioning, electric and telecommunications systems, this can be included in the CAR policy through corresponding extensions ofcover without making it necessary to issue two separatepolicies.A separate EAR policy is only meaningful if a strict distinc-tion is to be made between the structural works and theinterior finishing on account of different insurance inter-ests (principal/tenant). Since, however, it is impossibleboth physically and chronologically to separate the struc-tural works from the interior finishing, care must be takenin this specific case to ensure that the scope of cover isprecisely defined in relation to the concurrent CAR policy.

GENERAL

Unless explicitly stated otherwise, the following com-ments apply equally to the cover granted under a CAR and

Compared with normal building construction, thereare a number of additional risks associated with the construction and subsequent occupancy of high-rise buildings which can only be appraised by an experienced insurer. The project documents providean initial overview of these risks.

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an EAR policy. Both policies cover the construction orerection work specified in the Schedule against unfore-seen and sudden physical losses of every kind.

POLICYHOLDER

The interests of all parties involved in the constructionwork are normally insured by the principal. The group ofinsured persons or companies is therefore very large; boththe principal and the general contractor are policyholdersin a CAR/EAR policy, although all subcontractors are alsocovered. These are often specialists, particularly in high-rise construction. This explains why the general contractoris not the only party of interest to the insurer, for the spe-cial jobs undertaken by subcontractors can frequently rep-resent a greater risk. Here, too, the general contractor is liable as contractor to the principal. It is therefore essentialto obtain full information on the work of these specializedcompanies as well, in order to appraise the physical andmoral hazard.If – in deviation of the norm – only the contractor takes out CAR/EAR insurance to safeguard his own interests,then the contractual agreements reached between principal and contractor must be reviewed in order to as-sess the risk to be borne by the insurer. The risk for lossesdue to force majeure will normally pass partly or entirelyto the principal. This reduces the risk to the contractor’s insurer.

FORM OF COVER

It concerns all-risks coverage, i.e. every cause of loss iscovered unless explicitly excluded. This naturally meansthat the insurer must take account, in particular, of therisks from ground and soil and the exposure due to nat-ural hazards, especially windstorm and flooding. The termsof insurance must be clear. In very rare cases, it may benecessary to introduce a limit of indemnity for losses dueto natural hazards, such as earthquakes. This may be ne-cessitated by inadequate capacities or uncertainties whenestimating the possible maximum loss.

SUM INSURED

Particular expertise is required of the insurer when deter-mining the sum insured. As a rule, the approximate con-tract value at the beginning of the insurance term canserve as a provisional sum insured and is used as thebasis for calculation of the premium. However, the con-tract value must be regularly reviewed by the insured totake account of inflationary price rises or higher sums due to supplementary contracts during the constructionperiod, and this sum insured must then be adjusted cor-respondingly in the policy. The sum insured can also beincreased by a safety margin in order to avoid the dangerof underinsurance. If this margin exceeds the actual suminsured upon completion of the construction work, the insured is granted a corresponding premium refund. In all cases, however, the total sum insured is equal to themaximum indemnification for all claims payments. On theother hand, it is not advisable to wait until the end of theconstruction phase before adjusting the sum insured, asexperience has shown that the policyholder’s interest in

exact documentation of the final sum insured declinesafter conclusion of the construction work.

PERIOD OF COVER

Insurance cover is provided until the policy expires or untilthe construction work is finally accepted by the principalor until the building is taken into service or used, if this occurs before expiry of the policy. However, there are ex-ceptions, particularly in this context and especially if com-pleted floors are let earlier in order to earn income fromrentals or sales proceeds as soon as possible. In suchcases, a clear distinction must be made between the coverdefined for the CAR policy and that of the subsequent insurance for the building. In spite of all efforts to boostefficiency, construction work usually continues over sev-eral years, with the result that during risk assessment theconstruction schedule should be consulted in order to in-clude seasonal hazards, such as monsoon rains or autumngales.Extensive preparatory work (routing of supply lines, erec-tion of the retaining walls, excavation and water manage-ment) is necessary before work on the high-rise buildingactually starts. Insurance cover is also required for thispreparatory work, since losses can arise even in this phaseof construction.A so-called maintenance agreement is often concludedbetween the principal and the contractor for the periodafter completion of the construction work. Under theseagreements, the contractor is obliged to remedy any defects occurring in the building during the term of themaintenance agreement (usually 12 months). Two types ofinsurance cover can be granted for property losses in thisperiod:– Insurance of physical losses following maintenance

work (Clause 003: Maintenance visits), or– In addition to the aforementioned cover, insurance of

physical losses occurring during the maintenance periodbut caused by an event originating in the constructionphase (Clause 004: Extended maintenance).

LOSS ADJUSTMENT

In cases of physical damage to the insured contract works,the insurer will indemnify the necessary costs incurred forrestoring or replacing the damaged contract works. Therepair costs will sometimes be higher than the original expenditure up to occurrence of the loss. However, if thecost types are the same as those included in the sum in-sured, they will be indemnified in full. This is not the casewith costs which are first incurred during repairs (e.g. re-moving damaged parts in order to carry out repairs). Thepolicies recommended by Munich Re include such costsonly if this has been specifically agreed and a first-losssum provided for this purpose.This procedure should be applied above all to cleanupcosts (removal of debris) and loss-locating costs. In bothcases, the duty to indemnify depends on whether or notexpenditure was incurred in conjunction with an indemni-fiable loss. We believe that this procedure allows insurersto assess their liabilities more accurately. And it is also inthe interests of the policyholder, who can then decide on

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the amount of cover required in view of the potentiallyvery high “additional loss costs”. The same also applies toindemnification of additional planning costs which may beincurred due to repairs if the original planning costs werenot included in the stipulated sum insured or if new plansare required on account of the circumstances surroundingthe loss. Only those costs will be indemnified which arenecessarily incurred in order to restore the building to thesame technical condition as immediately before occurrenceof the loss. However, if the original condition is improvedor changed as a result of the repair, this also means thatany costs associated with such improvement or changewill not be indemnifiable. The same applies if other, morecomplex methods are used for the repairs; they, too, areonly indemnifiable to the extent that they were includedin the original sum insured. The agreed deductible mustin all cases be taken into consideration in the calculatedamount of indemnity.

RISK ASSESSMENT

Assessment of the physical hazard by insurers should bebased on the same considerations as those underlying thechoice of a certain construction method. In addition, how-ever, they must also consider, for example, whether a cer-tain method or material was perhaps only selected inorder to save time or money. The insurers must then determine whether, in the light of known risk factors, ahigher risk of physical damage was knowingly accepted bythe principal or contractor as a result of this choice.Assessment of the moral hazard always begins with theplanning process. The manner in which the planning hasbeen organized must be reviewed; for instance, to deter-mine whether principals assign the planning and super-vision of the construction work to their own office orwhether they retain various engineering offices for thispurpose. The question whether planning and executionwere done under time pressure and whether the scheduleallowed for adequate time buffers can also be of decisiveimportance. Last but not least, the contractors’ experienceon similar high-rise construction projects, and particularlythe quality of the contractors’ construction or erection per-sonnel, can also be of great importance when assessingthe moral hazard.

EXTENDED COVERS

The CAR policy can be suitably extended with the aid of various other standard clauses, including those applic-able to EAR insurance, in order to provide sufficientlycomprehensive cover for the erection work concerned. The following most commonly used clauses provide extended cover for political risks (Clause 001), cross liability (002), extended maintenance (004), overtime (006),airfreight (007), fire-fighting facilities (112) and designer’srisk (115).

5.1.2 Advance loss of profit insurance

The large proportion of borrowed capital required to fi-nance high-rise construction projects has made principalsincreasingly aware that conventional property policies willonly cover a limited part of the overall loss, but not theloss of operating profit or standing charges due to delayedcommissioning or occupancy following a loss.Even such additional agreements as contractual penaltiesor liquidated damages provide only inadequate relief here.For this reason, the existing CAR (EAR) policy can be ex-tended by means of an ALOP cover. The purpose of thisextension of cover is to insure the principal’s financiallosses due to delayed commissioning or occupancy fol-lowing an indemnifiable CAR loss during the constructionphase.

FORM OF COVER

ALOP risks are written in line with Section III in the Schedule to the standard policy for property cover. If theproperty policy provides for a very large scope of cover,this may have to be reduced to take account of the ALOPcover. This applies particularly to the exclusion of lossesfollowing delayed completion of the construction work asa result of earthquakes.Stand-alone ALOP covers without property insuranceshould as a rule be declined because, when it comes toadjusting property losses, the necessary information islacking and there is no way to influence the adjustmentprocess.

POLICYHOLDER

Since ALOP covers exclusively protect interests of theprincipal, the latter should be the sole beneficiary. In orderto ensure that they are able to exert their full influence inthe event of a loss, however, both the principal and thecontractor should be named as policyholders in the basicpolicy cover.Contractors on the other hand cannot obtain ALOP coverto insure their consequential losses – above and beyondthe property losses covered by Section I of the CAR policy– such as penalties, interest due on withheld warrantysums and other “soft costs”.Banks should also be excluded as policyholders, sincetheir interests should be regulated in the financing agree-ments concluded with the principal, independent of theterms and conditions of insurance.A special situation only arises in conjunction with the in-creasingly widespread “build-operate-transfer” (BOT) projects where principal and contractor act together andtherefore are joint usufructuaries of the building followingits completion. In such a case, they are both named policy-holders under the ALOP cover, but with due regard to thepossibility of a higher moral hazard.

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SUM INSURED

The sum insured is normally equal to the gross annualprofit, i.e. projected fixed costs and operating profit for thehigh-rise building. This gross profit is determined by de-ducting the variable costs from the sales or profit. Insur-ance is not required for these variable costs (e.g. cost ofelectricity, water, personnel), since they are not yet in-curred when the delay occurs.However, the principal’s possible losses are not limitedsolely to the lost profit from letting or leasing the high-rise building. The following can therefore also be insured:– “Ongoing rent costs” if the policyholder must pay rent

for continued occupancy of other business premiseswhen completion of the new high-rise building is delayed, since he or his tenants cannot move into thenew premises on schedule.

– “Ongoing interest charges” incurred by the principal ifhe cannot sell the building at the planned time and must repay the loans taken out to finance constructionof the building or if the interest due cannot be paid atthe planned time out of income from rental or leasing.

– “Additional costs” if the loss of profit can be avoided or reduced in this way, for instance by purchasing outside electricity, renting flats, office or computer capacities.

Loss-minimization expenditure will also be indemnified upto the value of the indemnifiable loss of profit which hasbeen avoided in this way.If the agreed period of indemnity exceeds one year, theprojected sum insured for the entire indemnity periodmust also be specified in addition to the one-year sum insured.

PERIOD OF INDEMNITY

The maximum period of indemnity to be specified in thepolicy should be sufficient to allow damaged or destroyedparts of the building to be repaired or replaced. Due to thedifficulties often encountered in removing rubble and inobtaining new licences, this can easily result in indemnityperiods considerably longer than the originally plannedconstruction period.

EXCESS

Time excess is always preferable to monetary excess withthis form of cover and should be equal to at least fourweeks per twelve months of construction time. In view ofthe long time required for the construction of high-risebuildings, this results in a highly desirable time excess ofseveral months.

The policy recommended by Munich Re for this cover pro-vides for a one-off application of the time excess, sincenumerous cases of physical damage during the construc-tion period will ultimately delay commissioning of thehigh-rise building, thus resulting in only one ALOP lossduring the agreed indemnity period.

CLAIMS HANDLING

The handling of claims, i.e. determination of the indemnifi-able period of delay in completing the building and the resultant loss of profit is normally complex and time-con-suming. For this reason, progress should be verified atregular intervals during the construction phase, so thatloss-related delays can be distinguished from those un-related to losses and so that their impact on the originalcompletion date can be traced.So-called one-off costs cannot be insured, i.e. sums whichare due for payment or which are lost in full on a fixeddate, such as tax benefits, seasonal business, lost ordersand licences.

5.1.3 Insurance of contractors’ plant and machinery

Construction plant and machinery can be insured underthe CAR policy, through Clause 202 in the EAR policy or ina completely separate contractors’ plant and machinery in-surance. The scope of cover is the same in all three cases.Basically, this concerns machinery insurance for contract-ors and is limited to external causes of loss. In otherwords, the insurance does not cover losses due to internalmechanical or electrical problems. In high-rise construction, such machinery and plant is re-quired above all for the retaining walls, foundation struc-tures and excavation. Cranes are used for construction ofthe high-rise building as such. However, care should betaken to ensure that all the plant and machinery is insuredand not just such highly exposed plant as cranes and scaf-folding. The sum insured should correspond to the re-placement value of the insured machinery and plant, sincethis is the only value that can be objectively determined;in the case of partial losses – which make up the bulk ofall losses – the repair costs can then be indemnified new-for-old without deduction. It is only with the much lesscommon total losses that the amount of indemnity is limited to the current value.Experience has shown that numerous individual lossesmust be expected in particular when insuring contractors’plant and machinery. Appropriate deductibles can there-fore reduce not only the claims burden, but also claims-handling costs, while at the same time creating an incen-tive for the policyholder to prevent losses and ensure theorderly organization of construction work.

86 HEAVY PLANT IN USE DURING FOUNDATION WORK

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5.1.4 Decennial liability insurance

This special form of cover for buildings originated inFrance. In accordance with the Napoleonic Code, all build-ings are insured against total or partial collapse for a period of ten years (hence the term “decennial”) followingtheir completion, provided that the loss is attributable to adefect or fault in the performance of one of the parties involved in construction during the construction phase.This form of long-term cover has only become establishedin a few markets and is normally limited to buildings, including high-rise buildings. The scope of cover varies.The commonest extended cover includes leaks in under-ground levels, facades and the roof, which can proveproblematical due to the frequently unknown long-termperformance of seals and the highly complex, cost-inten-sive repairs.

A distinction is made between countries, such as France,in which this cover is obligatory and markets which onlyoffer this form of cover in isolated cases.Technical inspection of the construction work by an inde-pendent inspection agency or engineering office is nor-mally essential before decennial liability cover can begranted. The availability of such cover is dependent onthis agency or office having submitted a satisfactory finalreport stating that it has no reservations as regards thestability of the high-rise building.The principal is the insured party and also beneficiary inthe event of a loss. However, the insurer can also seek recourse from contractors, subcontractors and suppliersif they can be held liable for the loss.Due to the long period of liability, insurers must make ade-quate provisions with regard to administration and whencarrying forward reserves.

5.1.5 Insurance of buildings, fire insurance

For property insurers, insurance of high-rise buildings is nothing unusual in terms of designing the policy. As inthe case of “normal” buildings, the policy is designedalong the lines of industrial or commercial insurance forbuildings and sometimes also of insurance for residentialbuildings.A distinction is merely made between two essential formsof cover:

NAMED-PERILS COVER

The model of named-perils cover is derived from the basicperils of fire, lightning strikes, explosions and crashes bymanned flying objects or parts thereof or of their cargo.This form of cover allows the insurer a very good over-view of the perils to be covered and ensures the trans-parency necessary for fixing prices.

This basic cover is normally extended accordingly with additional inclusions in line with individual requirements,such as– natural hazards: earthquakes, floods, windstorm, land-

slides, hail, volcanic activity, snow pressure, avalanches;– political risks: strikes, riots and civil commotion, sabo-

tage, possibly terrorism;– other perils: impact of vehicles, water damage, sprinkler

leaks, glass breakage, malicious damage, graffiti.

ALL-RISKS POLICIES

Policyholders in a number of markets are increasingly de-manding all-risks policies for high-rise buildings as well.This form of cover includes all of the risks under one pol-icy which are not explicitly excluded.Although these policies offer the policyholder extensive insurance cover, they must be examined with particularcare by the underwriter. Calculation of the premiums is nolonger transparent in these cases, since the extensivescope of cover may tend to “veil” the insured perils.A distinction must also be made from one country to thenext with regard to the scope of liability. Such politicalrisks as terrorism and sabotage, for instance, may be in-cluded in an all-risks policy without additional premium insome countries, but excluded from the standard cover inothers on account of local claims experience.Inclusions from non-property classes, such as third-partyliability and machinery breakdown insurance, are also in-creasingly to be found in all-risks covers.The owner of a high-rise building and its users or tenantsare frequently separate and distinct legal entities with dif-ferent policyholders, i.e. the owner for the building assuch and the tenant for its contents and furnishings. Forthe insurer, this may result in exposure to accumulation,which must be taken into account accordingly. Dependingon the purpose for which the building is used by its ten-ants, e.g. offices, computer centre, flats, hotels, possiblyalso commercial businesses (multi-occupancy building),the loss exposure can be quite substantial.

In conclusion, from the insurer’s point of view high-risebuildings are exposed to the same risks as other residen-tial and/or office buildings as far as the scope of cover isconcerned; for this reason, they are not different fromother risk groups with regard to insurability. Only the spe-cial characteristics of certain risk situations have a limitedinfluence on pricing (see PML, loss prevention). The pos-sibility of accumulation must be taken into account, how-ever, when the building and its contents are insured separ-ately.The policyholder’s primary interest is to obtain the mostextensive insurance cover possible in return for a premiumcommensurate with the risk.

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5.1.6 Loss of profit insurance

Standard covers or customized insurance (on request) are offered for the loss of profit risks mentioned in Section 4.9.

5.1.6.1 Loss of rent

The high-rise building owner’s interest in steady incomefrom rent is normally protected through loss-of-rent insur-ance. In accordance with the applicable General Termsand Conditions of Insurance (ABM 89), insurers in Ger-many will indemnify the insured loss of rent for the build-ing specified in the insurance contract, as well as for otherparts of the property which have been destroyed or dam-aged by specified perils. Where rented property has beendestroyed or damaged, tenants are entitled by law orunder the lease to refuse payment of part or all of the rent.The value insured is normally equal to the value of oneyear’s rent and the sum of ongoing ancillary costs for aperiod of one year.The loss of rent will be indemnified, at most, until thepremises are reusable, regardless of official restrictions onrestoration. If the tenancy ends on account of the damageand if the premises cannot be relet when restored even ifdue care and diligence have been exercised, then the lossof rent will be indemnified after this time until the prem-ises have been relet, but at most for three months. Unlessotherwise agreed, loss of rent is indemnified for a max-imum of twelve months as from occurrence of the insuredevent.On Anglo-Saxon markets loss of rent can generally be covered as a supplementary item under insurance ofbuildings. However, coverage ends when the rooms are finally restored, i.e. reusable, regardless of any furtherloss of rent until a new tenant can be found.In such cases, the owners of high-rise buildings of thetype described here are advised to take out loss of profitinsurance corresponding precisely with the terms of thelease. This applies in particular to the period of indemnityuntil the entire establishment has been economically re-habilitated; agreements with terms of up to ten years aretherefore entirely possible. Another advantage of loss ofprofit insurance is that it covers all additional costs, inso-far as they actually reduce the threatened loss of rent.Such costs include, for example, additional expenditurefor short-term emergency repairs, overtime for contract-ors’ employees and other trades, as well as special ad-vertising measures taken to find new tenants.

5.1.6.2 Additional costs

On the other hand, it is also perfectly possible that if abusiness is favourably and strategically located in thehigh-rise building, the tenants may have decided on along-term investment by concluding a lease over severalyears in order to protect their interests. The following circumstances may have to be taken into account:– The rental value of the premises at the time of the loss,

and probably throughout the remaining term of thelease, is appreciably higher than the rent actually paid,with the result that the tenant must expect to pay morein order to rent comparable premises elsewhere.

– Advance payments of the rent which have not yet beenamortized and which, under the terms of the lease, neednot be refunded in the event of a loss.

– Improvements in the value of permanent fixtures andfittings which have been financed by the tenant, butwhich have not yet been amortized and which, accord-ing to statutory regulations, he cannot remove when vacating the premises following a loss.

– Under the terms of the lease, the tenant is obliged tocontinue payment of all or part of the rent although thepremises cannot be used on account of the loss.

American insurers offer “leasehold interest coverage” tocover such eventualities. European insurers offering lossof profit insurance will indemnify the additional costs in-curred to minimize the impending insured loss.

5.1.6.3 Contingency planning

The more exposed a skyscraper’s position as a regional attraction and the more special the fixtures and fittings inthe rented premises, the greater the business-interruptionrisk, for it will probably be very difficult and exceedinglyexpensive to relocate business operations to suitable alter-native premises.The survival of a company may often depend on detailedand regular reviews to assess the feasibility of such con-tingency plans which would be triggered by a potentiallycatastrophic loss.Although loss of profit insurance can indemnify financialexpenditure for a calculated period of time, it cannot compensate for the loss of contact with key customers, a situation which could easily be averted by adequate contingency planning. The results of such perfect planningwere demonstrated following the bomb attacks on theCommercial Union building in London on 10th April 1992and the World Trade Center in New York in February 1993.

5.1.6.4 Prevention of access

Loss of profit insurance (business interruption, additionalcosts, etc.) can be extended to cover other risks, includingthe risk of a company being dependent on external oper-ations, institutions and special circumstances.Physical damage on the underground levels (garages) orapproach roads to a high-rise building due to fire, explo-sion, earthquake or flooding can lead to at least temporaryclosure of the entire building complex. Although the

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offices, shops, etc., have not suffered any property loss as such, they can expect profits to be affected in differentways – unless they have appropriate insurance (preven-tion-of-access insurance). American standard policies permit claims for damages for up to two weeks in suchcases.

5.2 Third-party liability insurance

As can be seen from what has been said so far, third-partyliability risks are also to be expected during the construc-tion of high-rise buildings.A distinction must be made between liability risks duringplanning and construction and those during occupancy ofthe high-rise building. The product liability risk of the manufacturers of the individual construction elements willnot be discussed further here.The high technical requirements to which engineers andcontractors are subject in the construction of a high-risebuilding naturally also pose a special challenge for the liability insurer in terms of recording, assessing andunderwriting such risks.

5.2.1 Insurance of the designer’s risk

A planning engineer or office can obtain professional in-demnity insurance to cover the liability risks associatedwith planning and site management.In the case of larger projects, a customized property policyis advisable with correspondingly higher limits of indem-nity which should also be available separately, instead ofan annual policy for twelve consecutive months.

SCOPE OF COVER

The scope of cover under professional indemnity insur-ance for civil engineers basically corresponds to the generally applicable professional indemnity insurance forarchitects and construction engineers.Insurance cover is provided for all statutory claims fordamages from errors and omissions by the insured in thedischarge of his precisely defined responsibilities.The geological conditions on site play an important parton account of the considerable load concentrations. If soilanalyses are performed by the designing engineer himselfor if he is contractually responsible for selecting, employ-ing and possibly supervising a geologist, then he may beliable for the consequences of inadequate soil analyses aswell as for incorrect soil analyses during the planningphase.

The most important scope of cover relates to the so-calledobject loss, i.e. loss or damage to the high-rise building assuch, insofar as such loss or damage is attributable to anerror for which the planner is responsible. However, object

losses should only be included if the designer and sitemanager have no interests in the widest possible sense inthe delivery, erection and execution of the work. Such in-dependence is only feasible with freelance engineering of-fices which have no financial or personnel links to the con-tracting companies and suppliers. Only then is it possibleto distinguish between a claim for damages based on faulton the one hand and a claim for performance and war-ranty, which is not covered by the liability policy, on theother. This condition is not met, for example, by engineer-ing offices which act as general contractor. In such cases,the liability policy should be limited to the second essen-tial scope of cover, namely third-party losses (bodily injuryand physical losses). The term of the object policy general-ly covers the planning and construction phase up to finalacceptance of the construction work with a period of sec-ondary liability of between two and five years as agreed.

RISK ASSESSMENT

Every high-rise building could be considered a prototypeon account of such different parameters as location,height, intended use, choice of materials and natural haz-ards. Particularly high standards are therefore imposedwith regard to the skill and experience of the planning en-gineer. Technical know-how is also required of the liabilityinsurer so that these difficult planning risks can be as-sessed and rated. The following criteria in particular mustbe taken into account when assessing the risk:– Qualifications and experience of the policyholder – Number of partners and number of engineers involved

in the project– Total fees – Contract price– Responsibilities and liabilities accepted – Construction method applied (Does it reflect the latest

scientific and technical findings? Have any comparableprojects already been completed?)

– Particular geological conditions, groundwater conditionsand natural hazards to be taken into account in the plan-ning (earthquakes, wind, possibly floods)

– Surrounding area (e.g. closely built-up city centres, pub-lic roads: damage due to falling parts)

– Planning period– Particular circumstances aggravating the risk (e.g. use of

new materials, facade elements)– Effect of construction work on the neighbourhood

(shadows, poor television reception, noise)

5.2.2 Insurance of the construction risk

The specific liability risk of the contractor responsible forconstruction of a high-rise building lies firstly in the risk ofinjury to his own employees (employers’ liability). Thisparticular risk of bodily injury is due to the fact that theworkers often have to work at dizzying heights and if a firebreaks out in the high-rise building, the number of casual-ties and fatalities is likely to be very high.

87 DANGEROUS WORKPLACE

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Secondly, the risks depend on the location of the high-risebuilding, as it will normally be located in a city centre,with dense traffic and narrow streets. Falling parts orcrashing scaffolding and cranes can cause physical dam-age to nearby main traffic arteries (urban motorway, tramways, railway lines) or to adjacent buildings, as wellas bodily injury to road/rail users and local residents. Interruptions to traffic can lead to consequential finan-cial losses. This highlights the particular risk of a majorloss during the construction phase of a high-rise build-ing.Moreover, the extensive foundation work and constructionof the underground levels make it necessary to excavatedeep pits, which often reach below the groundwater table.Depending on the type of retaining wall used, it may alsobe necessary to lower the groundwater table. The risk ofsubsidence, ground motion and even shear failures result-ing from such work must be assessed with particular caredue to the risk of major losses.

SCOPE OF COVER

The normal limits of indemnity are usually insufficient forsuch major projects or particularly exposed risks. Two al-ternatives can be chosen in such cases: either the limit ofindemnity in the annual policy is increased for the particu-lar object in return for a correspondingly higher premiumor separate liability insurance is concluded, tailored to theindividual project in question. For the insured, the latter al-ternative has the advantage that this limit of indemnity isavailable exclusively for this one project, thus eliminatingthe risk of limits in the annual policy being exhausted bylosses on other projects.

However, there is also another possible variation: high-riseconstruction involves not only the general contractor, butalso numerous other contractors (main and ancillary con-struction trades). In order to obtain uniform and adequateinsurance cover for all contractors, large or small, it isstandard practice for all companies to agree on a singlepolicy with a uniform limit of indemnity.The policyholder is frequently the principal who takes outthe policy on behalf of the contractors (third-party ac-count); the latter are then deemed to be insured persons.From the insurance point of view, they are treated as ifthey each had their own policy. However, it is also stand-ard practice to agree that the individual companies musttake out their own liability insurance with certain minimumlimits and that this liability insurance takes precedenceover the joint project policy. The project policy thus takesthe form of a surplus cover.The principal’s risk can also be included from the outset.Cover is occasionally also extended to include the risk ofindependent planners (property loss and third-party liabil-ity), albeit usually with considerably lower indemnity limits and, analogous to the procedure outlined abovefor the contracting companies, only subsidiary to higher-ranking basic covers.

What are the problems associated with an insurance solution employing a common project policy for all con-tractors involved in the construction work? Since the prin-cipal is the policyholder and some of the principal’s claimsagainst contractors/designers are also included in the insurance, this means that there is – at least formally – a certain degree of cover for first-party losses. In practice,however, the problem is mitigated by the surplus functionin that claims for damages are first examined and, wherejustified, also settled by the insurers of the mutually inde-pendent basic covers. Indemnity under the project policywould only kick in thereafter.CAR or EAR policies include the possibility of insuring the third-party liability risk of all contractors involved inthe construction work under Section II. In both policies,however, the indemnity limits of the third-party liability in-surance section are subject to certain limitations. An add-itional third-party liability policy known as the contractors’excess liability (CEL) policy can be concluded if higher in-demnity limits are desired, as may be assumed for high-rise construction, for instance on account of the particular-ly exposed nature of the risk.

RISK ASSESSMENT

When assessing the risk, it is important to appraise the potential degree of bodily injury losses within the frame-work of employers’ liability and particularly the possiblethird-party losses to the direct surrounding area as a result of falling parts, tools or even partial collapse of thehigh-rise building. Damage to adjacent buildings as a re-sult of lowering the groundwater table or damage due toground motion as a result of piledriving, underpinningand driving underpasses can often prove more expensive.The following aspects must be taken into account in par-ticular:– Contract price– Number of site employees and total payroll– Responsibilities and liability accepted– Construction methods and schedule– Location, surrounding area, neighbourhood– Particular geological conditions– Lowering of the groundwater table, blasting, underpin-

ning, driving underpasses– Contractor’s experience– Construction period, maintenance period, period of

secondary liability

5.2.3 Insurance of the operational risk

When the construction work is complete and the high-risebuilding has finally been taken into service, it is taken overby the operator or principal, who is consequently respon-sible for all losses suffered by third parties through the operation of the high-rise building. This operational riskwould be covered by the usual insurance for homeownersand property owners: it protects the owner in his capacityas owner and lessor of the high-rise building.

5 Insurance

The main risk lies inside the building, particularly if it isopen to the public. The most commonly occurring losseswill be personal accidents on improperly serviced stairs orelevators and bodily injury due to falling objects. However,the owner is only liable for causes within his sphere of re-sponsibility. These include regular servicing and mainten-ance of elevators, safety and control facilities, as well ascompliance with statutory regulations or official require-ments (e.g. fire protection). For this reason, the relevantmaintenance, safety and fire-protection schedules, as wellas fire procedures should be inspected by the insurerwhen underwriting a third-party liability policy for theowner and lessor of a high-rise building.The premium is normally calculated on the basis of thegross annual rent value, i.e. the total income from rent.

5.3 Problem of maximum loss

Due to the high concentration of values, the probablemaximum loss (PML) must be estimated separately foreach of the risk phases, also in the case of a high-risebuilding.

5.3.1 Construction phase

As is usual for all major projects, the PML estimate shouldbe based on a separate assessment of the risk. In the caseof high-rise buildings, fire will normally be considered aperil relevant to the risk and therefore form the basis forthe PML estimate.The measures required for active and passive fire protec-tion should not lead to any reduction in the PML, sincesome of these measures only become fully effective whenthe building is finished.This explains why fixed percentages are not specifiedhere; at best, a deduction for the often extensive and ex-pensive foundation measures can be justified when as-sessing the parts at risk, since these foundation measuresare not exposed to fire.Depending on local conditions, exposure to windstorm,earthquakes and natural hazards may also be of relevancefor the PML estimate during the construction phase.


The same considerations basically also apply to decennialliability insurance, except that here fire is replaced by thefairly rare risk of collapse. With major projects, it may also be advisable in view of the limited capacity availableworldwide to introduce a limit of indemnity in order to facilitate placement of the risk.

5.3.3 Operating phase

From an underwriting point of view, the fire PML is themost important element during operation of a high-risebuilding. The PML for a given risk refers to the probablemaximum loss which must be expected if the event oc-curs, with due regard to the conditions surrounding therisk and based on conservative estimates.When estimating the PML of “normal” risks, we base ourassessments on complexes, but this is not possible in thecase of high-rise buildings, as they usually comprise onlyone complex. What is important, however, is that we – unlike many other companies – do not take account of theexisting fire-protection facilities and precautions in ourPML estimate. The following are disregarded in particular:– Manual and automatic fire detection systems– Fire-extinguishing equipment, such as wall hydrants,

sprinkler systems, CO2 or inert-gas fire-extinguishingequipment

– Efficiency of the fire brigadeThese points are not considered to be factors which re-duce the PML because they occasionally fail when the in-sured event occurs. Structural fire-protection measures,such as fire-resistant construction practice, fire-resistantsealing and fire compartments (see Section 4.2.4.2), on the other hand, can be considered as PML-reducingfactors.Experience has shown that the total loss of a high-risebuilding is highly improbable, so that an assumed PML of100% should remain the exception. Although fires result-ing in total demolition of the high-rise building are knownto have occurred (see Section 4.2.3), this was essentiallydue to other reasons and not primarily to the impossibilityof repair. Moreover, the total sum insured was not paid asindemnification in these cases.On the other hand, we do not believe that it is right tospecify flat-rate percentages of the sum insured as thePML for high-rise buildings, nor to define a certain numberof floors as determining the PML, as is sometimes done.We believe that an individual approach is required whichtakes into account the following criteria:– Form of the building– Construction practice– Internal layout– Facade designHigh-rise buildings are frequently erected on a podiumwith one or more levels. When estimating the PML, it isimportant to establish whether a fire breaking out in thepodium can spread to the rest of building or whether thisis prevented by protected fire-resistant separations. Threeforms of building must be taken into account here: – small dot-like layout/towering building,– flat slice-like building (length of the building equals at

least three times its width),– large sprawling layout (base area in square metres

equals at least 50 times the height of the building in metres).

88 WORLD TRADE CENTER, NEW YORK

5 Insurance

The probability that entire floors will be gutted by fire ishighest in the case of the first group of buildings.With the second group, subdivision into fire compart-ments is more likely, if only on account of statutory re-quirements with regard to the length of rescue routes. Ifthe partition walls have been correctly designed and di-mensioned, a lower percentage loss may therefore be assumed per floor.An even larger number of fire compartments is to be ex-pected with the third group of buildings, and this shouldreduce the loss per floor still further. Going purely by theform of the building, the percentage PML must be highestin the first and lowest in the third group.Regardless of the form of the building, the combustibilityof the materials used and the fire-resistance period of theparts must also be considered. The characteristics of thesupporting structure and of floors as well as the fire-resist-ant elements protecting the openings to stairwells and ele-vator or service shafts are important in this respect. Thefacade design is a very important factor for vertical propa-gation of the fire and consequently for the PML. A firemust be expected to spread from one floor to the next ifthe window glazing is not fire-resistant and if the flashoverdistance between the windows on consecutive floors istoo short.The risk of fire spreading is even more serious if the build-ing includes an atrium, since the resultant chimney effectalso has to be considered.When estimating the PML, it is useful to consider thebuilding’s supporting structure and its finishings separate-ly. The finishing work must be taken to include all non-bearing inner and outer walls including panelling, allbuilding service installations and elevators, all doors, win-dows, floor coverings and ceilings.In the past, it was common to do a 50:50 split on support-ing structure and finishings, but this ratio has nowchanged to 30:70 on account of the more complex build-ing services and more extensive wiring in modern build-ings. Experience has shown that considerably less than50% of the supporting structure of a high-rise building willbe damaged by fire, depending on its type, particularly as regards its fire resistance. In the case of the finishings,on the other hand, the loss must be expected to be in theregion of 40–100% due, among other things, to damagecaused by smoke and fire-fighting water.The highest percentage losses are suffered by the support-ing structure and finishings in the first group of buildingsand the lowest by those of the third group. What has beensaid above must be considered one possible approach forestimating the PML and not as an algorithm, since numer-ous different criteria must be taken into account separatelyin each case.In addition, such covered items as cleanup and demolitioncosts, increased costs of working due to conditions im-posed by the authorities and price rises during the restor-ation period, must be added to the PML. These are normal-ly first-loss risk items which should be included 100%.

So far, we have only considered the building as such. Itscontents are normally insured separately, the policyhold-ers usually being the building’s users or tenants. If thebuilding is insured together with its contents, the PML forthe contents must be taken as a cumulative figure whenestimating the PML. Contents require similar considerationto interior finishings. Once again, special attention mustbe paid to “multi-occupancy buildings” (see Section 5.1.5).How appropriate is it to specify a terrorism PML for high-rise buildings? In our point of view, there is little point inspecifying such a PML, as we would not like to considerterrorism a “probable” event. Moreover, it is impossible togive any precise estimate of a loss due to terrorism andthe PML would always have to be set at 100%.A bomb attack is the most effective terrorist attack. It isperfectly conceivable that trained experts, such as special-ists in the use of explosives, could be used for the “mosteffective” result. After surveying the building, such spe-cialists can easily position their bomb or bombs in such away that it will cause the entire building to collapse.What is more likely, however, is that a car bomb contain-ing a large charge of explosives will be detonated in anunderground car park or in the immediate vicinity of thehigh-rise building. The extent of the destruction is conse-quently a matter of chance and therefore hard to estimate.It is necessary to adopt a country-specific approach to thisissue, also taking account of the building’s location andoccupancy. An office block in an industrial complex willundoubtedly be a less likely target for terrorists than acity-centre office tower. There have been sufficient ex-amples of such cases in the recent past.If cover for terrorism cannot be excluded for reasons ofmarket policy in a country with high exposure to terror-ism, then it is perfectly appropriate to assess the PML at100% of the sum insured.Earthquake exposure must also be taken into account forthe PML during the operational phase. The major earth-quakes experienced in recent years caused such extensivedamage to high-rise buildings as to make repair impos-sible (Mexico City, Kobe). Older buildings and particularlybuildings with “soft storeys” (see Section 4.4) were worstaffected.When estimating the earthquake PML in regions exposedto this risk, it is therefore important to establish whethermodern anti-seismic construction codes exist and whetherthey were also applied to the high-rise building under con-sideration. If these construction codes are known to havebeen violated or if there are any doubts in respect of com-pliance, then a PML of 100% should also be assumed forearthquakes.The same applies to windstorm, volcanic activity andother natural hazards in regions exposed to these particu-lar risks.

5.3.4 Accumulation control

This problem must be considered above all in conjunctionwith the perils windstorm, earthquake and fire primarily inrespect of buildings covered by CAR, EAR or fire policies.

5 Insurance

This naturally only applies to areas or cities with a corres-ponding concentration of values in the property insurers’portfolios.Munich Re has already stated its views on this subject in anumber of publications; it has also drawn attention to theneed for accumulation control and issued correspondingexplanations.As far as the natural hazards windstorm, earthquake andflooding are concerned, the values currently at risk in therespective exposure zones or specific catastrophe scen-arios are determined using computer-aided data analyses.The respective loss accumulation zones and correspond-ing loss potential are then determined for these catas-trophes.We will gladly answer any queries from our clients onsuch issues.

5.4 Underwriting considerations

Different construction methods, different finishings andthe exposure to external influences demand careful analy-sis of the resultant risks. For this reason, only approximaterates can be specified for insuring the construction andoperational phases of high-rise buildings, despite theavailability of statistical analyses extending over manyyears.

5.4.1 Contractors’ and erection all risks insurance

When determining the premium rate, different degrees ofexposure during construction of the high-rise building(foundations, structural works, finishing) must be takeninto account in the same way as the proportion of tem-porary auxiliary structures (e.g. retaining walls) and theirexposure during use. The following documentation should normally be available:– General drawing and layout plan of the site with an

overview of the immediate surroundings– Technical details concerning the construction method,

progress made and materials used– Breakdown of the contract price according to the most

important parts (foundations, structural works at under-ground levels/floors above ground, finishing)

– Schedule of construction work, particularly in conjunc-tion with regularly recurring natural phenomena (e.g.monsoon)

– Expert report on soil conditions– Description of the foundation method, retaining wall,

possible lowering of the groundwater table– Layouts, longitudinal and transverse sections of the

building in different planes, details of the most import-ant structural parts (e.g. facade connections).

The premium rates required for underwriting are deter-mined on the basis of an assessment of these documentsand of the structural analyses. Premium rates are not

specified here on account of the considerable scope forvariation and additional, highly commercial influences pre-vailing in the various markets.Where the deductible is concerned, difficult soil conditionsand the exposure to windstorm due to structural reasonsor progress in construction must also be taken into ac-count in addition to the long time frequently required forthe construction work.If necessary, it must be possible to calculate the risk by including suitable special terms, limits of indemnity or exclusions. This applies particularly to high-rise buildingsover 500 m, as their exposure to windstorm has not yetbeen sufficiently investigated, and when using inadequatelytested materials and construction methods.

5.4.2 Contractors’ plant and machinery

When determining the premium rate, the number and period in use of the highly exposed cranes must be takeninto account in addition to the scope of cover. Elevatorsfor transporting materials to great heights are less ex-posed to loss, since they are firmly connected to the shellon the outside or are located inside the high-rise building.


The level of premium rates for this cover is also largelydependent on the specific market, the market situation and scope of cover. For this reason, the premium rate canrange between 5‰ and 15‰ for the ten-year period. In addition to the premium, the principal must also bear thecosts of technical inspections; these costs vary in line withthe size and complexity of the project.The waiver of a deductible is prescribed by law in somemarkets; as a rule, however, the long term of this covershould be taken into account when determining theamount of excess.

5.4.4 Insurance of buildings, fire insurance

As with all risks, the terms, quality of the risk and price arecomponents which must be taken into account whenunderwriting high-rise buildings.Where the terms are concerned and particularly in con-junction with the scope of cover, the statements made inSection 5.1.5 apply, with “named perils” and “all risks” asthe two main forms of cover.All the criteria listed in Section 4.2.4 must be considered inorder to determine the quality of the risk. Under no circum-stances should the underwriter assume that all statutorymeasures have been taken or that the quality of the riskis satisfactory simply because of compliance with the regulations. As the cases outlined in Section 4.2.3 haveshown, the standard of protection applying when the high-rise building was erected may well be far below the stand-ards required today. It therefore follows that the con-struction practice and standard of protection must be con-sidered individually. Particular attention must be paid to

5 Insurance

structural fire protection, as well as sprinkler protectioncommensurate with the risk.Although quantitative statements cannot be made, theprobability and frequency of a loss occurring and theamount of loss to be expected will be lower if the qualityof the risk is “good” than in the case of inadequately pro-tected buildings. Higher shares can therefore be written inthe case of “good” risks.In the case of extended basic cover, the risks due to sup-plementary perils, e.g. earthquake, windstorm, hail, flood-ing, water damage and glass breakage, must naturallyalso be taken into account in the underwriting. The samealso applies to all-risks covers, special attention being de-voted to the exclusions (see Section 5.1.5).General statements cannot be made here with regard tothe price, i.e. premium rate. Claims experience and localexposure play a vital role in pricing, as do commercialconsiderations. Above all, the premium calculation alsohas to take into account supplementary perils such as natural hazards and political risks on the basis of individ-ual loss exposure.The quality of the risk is naturally also reflected in theprice; in other words, appropriate protective measures orgenerally “good” quality of the risk will result in a corres-pondingly lower premium rate.

5.5 Reinsurance

In the majority of cases, there should be no particularproblems in reinsuring individual high-rise buildings, pro-vided that the necessary conditions have been met for theindividual classes (contractors’ all risks, erection all risks,insurance of the building, fire insurance, decennial liabilityinsurance, third-party liability insurance). On account ofthe different forms of cover, the main thing is to ensurethat the policies in question are allocated to the appropri-ate classes, e.g. engineering insurance, third-party liabilityinsurance and fire insurance (as described in detail in thepreceding sections) and that the risk is properly assessedin line with the respective policy.Special need for reinsurance may arise, however, in thecase of individual major high-rise-building risks and exten-sive accumulation risks resulting from the concentration ofnumerous high-rise buildings within a small area. This isindeed the case with skyscrapers of record-breakingheights and sums insured due to the high fire PML or therisk of earthquakes or windstorm in areas particularlyprone to such hazards. The need to insure these risks willnormally exceed the capacity of the local insurance mar-ket. The same also applies with regard to decennial coverfor such risks.However, even reinsurers with the soundest financial back-ing cannot accept unlimited liability. In some cases, it willtherefore be necessary to introduce a limit of liabilitywhich makes the risk more manageable and easier to cal-culate; this will also ensure that the available underwritingcapacity can be fully utilized. The type of limits to be speci-

fied in the classes concerned should be decided in accor-dance with individual requirements.In addition, limits of liability also facilitate matters for in-surers and reinsurers; liability accumulations can be deter-mined and updated more easily and precisely. This is par-ticularly important in countries or regions which are con-stantly exposed to natural hazards, such as Japan or Cali-fornia, where comprehensive insurance cover is providedfor a large number of high-rise buildings in an area of in-tense seismic activity and where there is consequently asubstantial accumulation risk.Even in these extreme cases, however, the demand for ad-equate insurance cover is and was satisfied by insurersand reinsurers working together as partners. This is par-ticularly true of insurance markets marked by high invest-ment and growth. The benchmark has been raised interms of what insurers require and expect of reinsurers,especially with regard to know-how, professional compe-tence, market experience, innovativeness and ultimatelyalso adequate capacity combined with long-term financialstrength.Munich Re is optimally positioned to meet these chal-lenges.The lead it has built up globally over the decades in termsof experience and information is based on extensive data-bases. With the help of modern computer-based tools, thelatest data can be rapidly made available to the insurers.Comprehensive geo-scientific and underwriting analysesof these data by experts at Munich Re’s head office and inthe engineering offices around the world ensure that nat-ural hazards and loss potential can be reliably assessed.Experienced underwriters are available to our clients atmore than 45 business units and subsidiaries in our inter-national organization, all of which are linked online to thehead office. This enables us to advise prospective clientson assessing risk, defining the terms of insurance, and determining and providing the required reinsurance capacity.During the period of cover, our specialists can actively participate in inspections, loss prevention or settlementof complex losses.Extensive know-how and the courage to take innovativesteps make it possible for our specialists to provide our clients with professional support in developing newconcepts for cover or new insurance products.We will gladly answer any queries by our clients, providefurther information or outline possible solutions in con-nection with reinsurance and our range of services.

89 EXTERIOR HOIST

6 Summary and outlook

6

6 Summary and outlook

Most of the statements made here, however, will continueto apply to future high-rise buildings. Despite certain reser-vations and all economic bottlenecks, the quest to reachfor the sky and erect higher and higher buildings goes on,particularly in Asia.

For this reason, we as insurers and reinsurers will con-tinue to devote our attention to these projects in the newmillennium. We are also confident that, thanks to ourworldwide know-how and long-standing experience, wewill be able to offer our clients solutions in line with thespecific risks involved.

1 Die Bezeichnung höchstes Bauwerk der Welt bean-sprucht zur Zeit der Fernsehturm von Toronto, der nebendem Ontariosee 553 m in den Himmel ragt. Das zweit-größte Bauwerk ist der Fernsehturm von Moskau mit537 m.

2 Eine Geschoßflächenzahl von 12 bedeutet, daß dieGesamtfläche aller Geschosse über Straßenniveau maxi-mal das Zwölffache der Grundstücksfläche betragendarf.

.3 Bentonit ist ein spezielles Tonmineral, das das Mehr-

fache seines Gewichts an Wasser absorbieren kann unddabei auf das 8–15fache seines Volumens anschwillt. Es bildet an den Wänden des Schlitzes eine Schicht,wodurch dieser gegen Materialeinbruch stabilisiert wird,ohne den Aushubvorgang zu beeinträchtigen.

4 Weitere Details sind in unserer Brandschutztafel nach-zulesen.

5 Advance loss of profit.

The historical and technical development of high-risebuildings as seen from the point of view of insurersand reinsurers has been outlined in the individual sections of this publication. Needless to say, develop-ment does not stand still, and therefore by the timethis publication appears in print some of the technicaldetails described here may already have been super-seded by research, progress and the pressure of costs.

Picture credits

Page Picture No. Title Picture credits

Cover 01 Manhattan, New York Image Bank, A. Becker, Anzenberger, Loccisano

6 02 San Gimignano Picture Press, Riedmüller

7 03 Monadnock Building Library of Congress

9 04 The Tower of Babel AKG, Berlin

10 05 Equitable Life Building Museum City of New York

10 06 Home Insurance Building Philipp Holzmann, Frankfurt a. M.

10/11 07 New York panorama Image Bank, A. Becker

12 08 HongkongBank Headquarters Building, Hong Kong HongkongBank

12 09 Messeturm, Frankfurt am Main Werkfoto HOCHTIEF, Essen

13 10 Petronas Towers, Kuala Lumpur Munich Re

15 11 Hong Kong skyline Pacific Century, Hong Kong

16 12 Flatiron Building, New York Photonica, B. Hubert

18 13 La Grande Arche, Paris Munich Re

19 14 Canary Wharf, London Munich Re

20 15 Traditional and modern buildings in peaceful co-existence Laif, Arthur Selbach

23 16 Chrysler Building, New York Image Bank, B. Frommer

27 17 Details from planning documents Munich Re

28 18 Extract from a technical report Munich Re

29 19 Opening in an apartment complex Munich Re, J. Eber

30 20 Large-bore pile foundation process Bilfinger & Berger

30 Various stages in the diaphragm wall process Bauer Spezialtiefbau, Schrobenhausen

32/33 21 Diaphragm wall rotary cutter Bauer Spezialtiefbau, Schrobenhausen

34 22 Retaining wall to protect neighbouring buildings Munich Re

34 23 View of a building pit with completed retaining wall Bauer Spezialtiefbau, Schrobenhausen

36/37 24 Examples of high-rise buildings with steel skeletons Munich Re, A. Kleiner

38 25 Deformation and bending momentum due to wind with the core construction method Munich Re

38 26 Background: Commerzbank Building Minimax

39 27 Deformation and bending momentum due to wind with the outrigger truss method Munich Re

39 28 Examples of core construction methods and bundled tubes Munich Re

40 29 Varying load distribution with tubes and bundled tubes Munich Re

41 30 Example of the arrangement of bundled tubes Munich Re

41 31 Steel skeleton Büro X

43 32 View from the headquarters building/Headquarters of BMW A. G. in Munich Pressestelle BMW A. G., Munich

44 33 Facade assembly Munich Re

47 34 Ceiling installation Top: Munich Re

47 35 Double flooring Bottom: Fa. Mero, Würzburg

50 36 Elevator in the World Trade Center, New York Visum, Michael Wolf

51 37 Elevator demonstration by Otis Left: Otis

51 38 Maintenance Right: Laif, REA/P. Bressard

52 39 Renovation of a high-rise building Top: Werkfoto BASF

52 40 Pile-driving machinery for working in basement floors Bottom: Bauer Spezialtiefbau

55 41 Petronas Tower Munich Re

56/57 42 Trend towards ever-taller modern high-rise buildings Büro X

58/59 43 The Millennium Tower – a vision for the 3rd millennium Forster and Partners, London

60/61 44 Petronas Towers, Kuala Lumpur, Malaysia Munich Re

62/63 45 Sears Tower, Chicago Anzenberger, G. Sioen

64/65 46 Empire State Building, New York Visum, J. Röttger

66/67 47 Messeturm in Frankfurt am Main Laif, C. Emmler, P. Langrock

69 48 Additional heat recovery via piling foundations in the Commerzbank high-rise building Minimax

71 49 Fully automated building site Obayashi Corporation, Japan

72/73 50 Jin Mao Building Shanghai Educational Publishing House

74/75 51 Shanghai Pudong Airphoto International Ltd./Pacific Century Publishers Ltd.

76/77 52 New York Visum, M. Wolf

76/77 53 China, Guangzhou action press, SABA-Laif, REA/Sinopix

78/79 54 New York Image Bank, A. Becker

80/81 55 New York: view from the World Trade Center Visum, M. Wolf

82/83 56 New York Munich Re, J. Eber

87 57 Fire in the Broadgate Building, London: sunken roof support beams Munich Re

88 58 Fire-protection information Munich Re

90/91 59 Escalator destroyed by fire Munich Re

92/93 60 Fire in the Meridien President Tower, Bangkok Munich Re

94/95 61 Meridien President Tower, increased risk of fire during the final fit-out phase Munich Re

96/97 62 Difficult fire-fighting conditions in the Meridien President Tower Bangkok Post

98 63 Combustible waste increases risk of fire Munich Re

100 64 Limited evacuation routes through smoke-filled stairways Bangkok Post

101 65 Hong Kong, fire in the Garley Building South China Morning Post

102 66 Towering inferno Munich Re

Picture credits

103 67 Difficult fire-fighting conditions Munich Re

106 68 Special coating on the steel skeleton guaranteeing adequate fire resistance Top: HongkongBank, Minimax, Eissing-Kister

106 69 Fire-detection system in the Messeturm in Frankfurt Bottom: HOCHTIEF/Landis & Gyr

109 70 Atrium in a bank building HongkongBank

112 71 Dynamic-pressure approaches: effects from friction impact wind speed Top: Munich Re, A. Kleiner

112 72 Typhoon tracks for Japan and California Bottom: Munich Re

113 73 Representation of wind impact on a building’s ground-bearing pressure Munich Re, A. Kleiner

116 74 Impact of earthquake loads on the centre of gravity Top: Munich Re, A. Kleiner

116 75 50 t and/or 90 t heavy dampers Bottom: Mitsubishi Heavy Industries Ltd.

117 76 Effective arrangement of dampers in high-rise buildings Mitsubishi Heavy Industries Ltd.

119 77 Earthquake in Kobe, Japan Munich Re

120 78 Corroded supply lines Munich Re, W. Schromm

120 79 Tension crack in a crosslinked polyethylene pipe Munich Re, W. Schromm

124/125 80 Blasting of a high-rise office building Iduna Versicherung

128/129 81 Interior of a high-rise building following a bomb attack Munich Re, J. Eber

130/131 82 Wooden panels on a glass facade destroyed by a car-bomb attack/Interior view of one floor Commercial Union, G. Evans

133 83 Aircraft debris after a plane ploughed into the Empire State Building Associated Press

134 84 Aircraft crash onto a block of flats in Amsterdam action press, F. Bründel

135 85 Bomb attack on a federal government building in Oklahoma, USA action press, SABA

143 86 Heavy plant in use during foundation work Bauer Spezialtiefbau, Schrobenhausen

146 87 Dangerous workplace Laif, REA/Sinopix

150/151 88 World Trade Center, New York Laif, P. Gebhard

154 89 Exterior hoist Munich Re

References

Title Author Publisher

Architektur des 20. Jahrhunderts Gossel/Leuthäuser

Architektur und Städtebau des 20. Jahrhunderts Lampugnani

Das Hochhaus in Gegenwart und Geschichte Goldberger (1984) DVA Stuttgart

DIN 1055, Part 4 Issue 8/86, 5/89

Elevators and Escalators Strakosch John Wiley & Sons, New York

Erdbebenprognose Geo 3/96

Facility Management 1/95 Bertelsmann Verlag

Fassadengestaltung Dr. Gartner

Fire Letter No. 24 Munich Re

Hongkong, Architekturmuseum Frankfurt a. M. Exhibition catalogue (1993–94) Prestelverlag

La Grande Arche Tete Défense (1990)

Marvels of Engineering National Geographic

Massivbau Vertiefungsvorlesungen J. Schlaich Universität Stuttgart

Messeturm Frankfurt a. M. Kolodziejczyk Technik am Bau (Periodical)

Messeturm Frankfurt a. M. J. Murphy Schriften zur Architektur der Gegenwart

MR Handbook “Water Damage Insurance” Munich Re

Preliminary Report on the Northridge Earthquake WSSI

Schadenspiegel 1/84 Munich Re

Schadenspiegel 1/95 Munich Re

Schadenspiegel, Special issue 1994 Munich Re

Skyscrapers Starrett Charles Scribner's Sons, New York

Special publication “Earthquakes of the Caribbean Plate” Munich Re (1976)

Special publication “Earthquake Mexico ’85” Munich Re (1985)

Special publication “Windstorm” Munich Re (1990)

The Empire State Building Theodore James, Jr. Harper & Row, New York

The Skyscraper Book Giblin T. Y. Crowell, New York

Tuned Active Dampers Mitsubishi Heavy Industries

Wie man Wolken kratzt P. v. Seidlein

Wolkenkratzer – Ästhetik und Konstruktion J. Schmidt Dumont Verlag

A publication of the Munich Reinsurance Company

© 2000Münchener Rückversicherungs-GesellschaftAddress for letters: D-80791 MünchenGermany

http://www.munichre.comE-mail: [email protected]

Design: Büro X, Hamburg

Order number 2840-V-e

The paper used for this brochure was produced without chlorine bleaching.

Wooden panels on a glass facade destroyed by a car-bomb attack/Interior view of one floor

HighRise Building Construction Profile

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