HIGH RISE BUILDINGS

A Seminar By-

AR. SAHID AKHTARMALIK SANDAL ART &

ARCHITECTURE COLLAGE, BIJAPUR, KARNATAKA

Massachusetts General Laws define a high-rise as being higher than 70 feet (21 m). Most building engineers, inspectors, architects and similar professions define a high-rise as a building that is at least 75 feet (23 m).

Davis Langdon (2002) states that it is not possible to define high rise using absolute measures. They believe that “tall buildings are therefore best understood in relative terms as buildings whose planning, design, construction and occupation is influenced by height in ways that are not normally associated with more typical, local developments.”

For the sake of this study, the terms tall building and high-rise shall be used for structures with approximately eight or more stories while towers are tall buildings with a slender shape.

HIGH RISE BUILDINGS

Economics of high-rise buildings

The high rise is a necessary response to urban sprawl. Almost half of the world’s population lives in the cities, and this trend is increasing. The skyscraper has many potential economic advantages where there is minimal land use as the amount of usable space per available land area is maximized. High rises still have many economic benefits as: Lowers operation and maintenance costs; Increases return on 9 investment; and Enhances public image.

Green building has proven effective in minimizing industry impacts on air and water quality and protecting natural ecosystems. It has also been shown to increase building value by improving cost performance, enhancing occupant comfort, and creating positive public perception.

Tall building requires an integrated, multi-disciplinary design process and a "whole-building" systems approach that considers the building's entire life-cycle (from planning, design, and construction to operation and maintenance, renovation, and demolition or building reuse). Together, these provide the means to create solutions that optimize building cost and performance

FIRST COST (INITIAL COST)

High Rise as a sample of high tech is assumed to cost a fortune. Towers as lab benchmark for sustainability

Many sustainable towers especially in Europe and Asia have been designed with cutting edge technologies and pioneering designs.

The first cost on those high rise structures could be substantially higher than conventional budgets, such as Commerzbank in Frankfurt, Germany designed by Norman foster and the SOM design of Pearl River Tower in Guangzhou China. The Guangzhou project cost over eight times the Chinese national average for high rise projects of its type.

LAYOUT AND SPACE

Layout and Space design is the cadenza of a symphony to the architects. A great design can significantly improve the sustainability of the high rise.

Service core

The size and location of the service core in a high rise building play a predominantly part in the whole design. That is well stated by Ken Yeang in his High-rise Elevator Cores (2002). He believed the arrangement of primary mass position can help to shade or retain heat within the building form. Of the various possible service-core positions i.e. ‘central core’, ‘double core’ or ‘single-sided core’, the double core is to be preferred.

The benefits of a peripheral service core position are:

! No fire-protection pressurization duct, resulting in lower initial and operation costs

! A view out with greater awareness of place for users

! Provision of natural ventilation to the lift lobbies. (and thus further energy savings)

! Provision of natural sunlight to lift and stair lobbies.

! A safer building in event of total power failure.

! Solar buffer effects and/or wind buffer effects.

Cores provide a path for building services, vertical transportation and a means of escape, as well as contributing to the structural stability of a building. For tall buildings with repetitive floor plates, the efficiency of service cores is crucial to their viability. Attention in the design process is given to the service core by parties with separate aims: lift engineers, building services engineers, structural engineers, architects, quantity surveyors, the District Surveyor, the fire engineer, the Fire Brigade. Design teams may review many options of core configuration to meet the different requirements of each discipline. Developers view cores as a loss of lettable space and apply pressure to minimise the core footprint. In general, the more time spent on the core design, the more sustainably efficient it is.

Commerzbank: Frankfurt, Germany, Norman Foster

Winter gardens allow vast amounts of light deep within the building and provide pleasant views to those working deeper within the building.

Creating a central atrium space in a high rise building

Centralized core area for circulation, mechanical, and other basic building needs.

The core functions were pushed to the outer corners of the building to make way for the atrium space.

Winter gardens had to be rotated around the facade of the building.

Commerzbank: Frankfurt, Germany, Norman Foster

The central atrium, free of structural members, was essential to provide light

both vertically, from the glass roof at the atrium’s top, and horizontally, from

the winter garden facades to the office across the atrium

Paying more attention to the configuration of office floor plans, favoring those with fewer columns, reduced glass-to-core depths, and more glass. And mixed use comes of age.

The 27,500-sf floor plates have column-free lease spans of 61 feet in the north-south direction and 50 feet in the east-west direction.

All internal columns were pushed out to the perimeter and spaced 40 feet apart to enable an "infinite variety in terms of office layouts.

The height and the open space are benefit for the natural lighting.

The plan geometry of the tower serves to reduce energy consumption in three ways;1. The curves shaped of the buildings in pinched ends allow sunscreens to effectively shade the glass at these exposures during the peak summer months. The geometry also allows the sun to heat the building during the limited heating season, as the sun angledescends below the sunscreens on the north facade.

2. The shallow dimension of the tower slab, 17.5 meters at its greatest dimension allows the prevailing winds to actually flow through the entire with of the building, naturally conditioning the interior spaces.

3. this narrow slab dimension coupled with full-height glass reduces the need for general office illumination for much of the day, which significantly reduces electrical energy consumption on the office floors

EnvelopeFor high-rise developments, the need to reduce energy should

drive the use of high performance building envelopes and hence reduce perimeter heating to a level that can be offset by passive solar heating and internal gains. Envelope is also essential to filter, channel and deflect critical natural forces, to create an internal environment geared towards the building’s function, to provide light, heating, cooling, sound modulation and fresh air for the comfort of the occupants.

The building envelope, or “skin,” consists of structural materials and finishes that enclose space, separating inside from outside. This includes walls, windows, doors, roofs, and floor surfaces. William Burke (1996) pointed out there several factors affecting envelope design. One of the most important is climate. The second is what occurs inside the building. Most LEED certified high rises claimed they used high performance, glazing, high-insulating building envelope.

Double skinDTI research on commercial buildings has shown that double skin buildings are able to reduce energy consumption by 65%, running costs by 65% and cut CO2 emissions by 50%, in the cold temperate climatic prevalent when compared to advanced single skin building. Cost exercises have shown that buildings employing a double skin may cost as little as 2.5% based on gross internal floor area.

Solar shading

Flats with large windows facing south, east and west can over heat during summers due to excessive solar gains. Horizontal shading devices are widely used over the windows facing south, such as, overhangs, light shelves and external louvers. The shading is designed to let direct winter gain but must protect against the summer sun.

Vertical shading devices are used for the windows facing eastern and western directions, solid or opaque, and use flat or sloped designs. Fixed and movable exterior louvers running horizontally or vertically across windows can also be used to reflect and diffuse sunlight. In some cases PV panels are mounted on top of the solar shading to generate electricity.

Reduce perimeter heating

Filter, channel and deflect critical natural forces

Provide light, heating, cooling sound modulation and fresh air for the comfort of the occupants

Structure (Current practices)

According to Greg Cox and Oscar Faber (2002), In broad terms, steel-framed buildings with a rigid frame can be economical for medium rise buildings up to 20 storey; a vertical steel shear truss at the central core of the building can be economical for buildings up to 40 storey; and a combination of central vertical shear trusses with horizontal outrigger trusses is most suited for up to 60 storey, this being the most common form of tall building structure in the US. For even taller buildings, it becomes essential to transfer all gravity loads to the exterior frame to avoid overturning effects. Rigid framed tubes braced tubes and bundled tube structures have been developed to reach up to over 100 storey in buildings such as the Hancock and Sears towers in Chicago. Outside the US, steel is not so readily available and construction practice favors concrete. Rigid concrete frame systems can be economical up to 20-storey; concrete walls forming the central core can be economical up to 40-storey; and concrete-framed tubes can be economical up to 60 -storey, with tube-in-tube structures and modular tubes used for very tall buildings. A combination of concrete and steel structures is often the most efficient form, utilizing the best characteristics of each material. Research into the performance of concrete-filled steel tubs has enabled their use at main supporting columns in some mega-structures in China. In the UK, the most common form of structure in buildings up to 50 stores is a reinforced concrete shear core used to stabilize the building against wind, with composite concrete floor slabs on a steel frame used to carry the building’s gravity loads to the foundations.

A comparison of the environmental performance of concrete and steel systems found that pre-cast concrete plank floors on steel beams has the least embodied energy. This structural type appears to have the necessary flexibility for future use of the building and integrates well with the building services.

Experimental structures

High rise structures have large potential to be integrated with the green energysystems, especially with wind turbine. Nowadays this is popular topic for scholars to research how to combine or mounted wind turbines with high rise structures for the generation of electrical energy for the building itself or for export. According toProfessor Peter Land (2004) there are several experimental structures have beendeveloped as the followings.

Light pipe transmission is also used in the experimental structure. “In this project the entire building and its structure is shaped around the light-pipe or light- flow concept.

Light is captured externally at the perimeter of the building every eight double floors, and channeled into and downward through the center of the building using high Fi

Light pipe transmission is also used in the experimental structure. “In this project the entire building and its structure is shaped around the light-pipe or light- flow concept.

Light is captured externally at the perimeter of the building every eight double floors, and channeled into and downward through the center of the building using high

performance reflectors.”8 Cross atria project showed in figure 3.22 “has wide atrium,

which penetrates through a slab-like building orientated

east west”. “An atrium opens on the south side

penetrating horizontally, then drops vertically through

eight floors, exiting horizontally on the north side”

Clustered tube structure developed from the co-supportive concept, was applied in the design of Jinling Tower by the San Francisco office of SOM for Nanjing, China. The square plan twists 90 degrees as it rises 320 meters (1,056 feet). James S. Russell (November 2004) introduced this building in his article: “Above office floors, recesses add windowed perimeter to 27 levels of apartments. The recesses grow deeper on the top 23 levels, which are devoted to an atrium hotel.”

Structural SafetyAfter the September 11 attack, high rises are seeking

for optimum robustness and structural redundancy with enhanced connections at its core and columns, alternate load paths and hardened columns in the lobby and loading dock.

The 111 South Wacker Drive looked much different before 9/11 (first threerenderings from left), with massive diagonal columns cradling a 40-story steel-and-glass structure 120 feet off the ground. Local developer John Buck decided to scrap the initial design after prospective tenants expressed concern for the building’s structural bravado in the wake of 9/11.

HVAC

The amount of energy used annually by heating, ventilating, and air-conditioning, HVAC systems typically ranges from 40 to 60 percent of the overall energy consumption in a building. HVAC systems also affect the health and comfort of building occupants. HVAC system is a complex process reflecting the details including the building’s use, occupancy patterns, density, passive solar opportunities, office equipment, lighting levels, comfort ranges, specific needs, envelope, and plan for effective ways to meet future load increases without sacrificing current energy requirements. The computer-based simulate software such as DOE 2.0, eQUEST, would help a lot to select equipment and evaluate the interaction between building systems.

Those projects certified by LEED also use many detail ways to improve the running of their HVAC systems and save energies. For instance:

Motion sensor controls were installed in all conference rooms so that the HVAC system would only be "on" in these zones when it is actually needed. All motion sensors to turn off after five to seven minutes of no movement. On-site black water reuse system to supply the HVAC cooling tower; under floor air delivery and commissioning Filters, with fresh air supplied at a rate 50% higher than mandated by current code.

CFC/HCFC-free natural gas-fired absorption chillers.

Variable-speed drives on all fans and motors.

• Individual air-handling units on each floor, with local control to ensure minimum use of the system.Further more, experts suggested those approaches in performing the analysis before HVAC design, all of which can be designed with architecture design.

! Explore passive solar strategies and non-energy-intensive HVAC and lighting opportunities

! Consider the building envelope and integrate this with general architectural issues such as solar strategies, glazing, day-lighting, and access.

! Fine-tune the proposed building footprint and orientation to maximize energy benefits. ! Recognize that thermal mass can be beneficial to reduce after-hours environmental conditioning and morning warm-up loads

! Optimize the energy benefits for each building facade.

! Review the interaction between daylighting and artificial illumination.

! Consider architectural elements to reduce direct solar radiation into the occupied space when not desired (cooling load avoidance).

! Control the infiltration of unwanted air

! Consider increased insulation levels for various systems to reduce loss factors.

! Consider vapor barriers to reduce latent (moisture) loads.

! Reduce internal heat gains

! Design systems and components for ease of maintenance.

! Incorporate ventilation for healthy indoor air quality and balanced energy use.

Lloyds Register of Shipping Building

In 1995 the Richard Rogers Partnership won the competition for the Lloyd’s Register of Shipping, a 15-storey 250,000 sq. ft. building in Fenchurch Street. The owner-occupier client wanted a leading edge energy efficient building for 1,500 people. The initial proposal was for a mixed mode air-conditioning system, offering the combination of opening windows and mechanical ventilation, but it became apparent that the original concept was unviable for two main reasons.

Firstly, the occupants should not be exposed to the poor external air quality in the area and,

secondly, they should not be exposed to ambient traffic noise from open windows.

The air-conditioning system chosen for the building combines chilled beams and displacement ventilation supplying low velocity air near floor level. The contaminated warm air is exhausted via driven fan ducts.

The slender floor plate of the upper storeys assures maximum access to daylight. Artificial lighting is supplied as supplementary to day-lighting, but due to the emphasis on natural lighting and the use of sophisticated lighting control systems, the building requires 35 per cent less electric lighting than the average London office building.

A major aspect of the building’s design is a strong emphasis on the avoidance of the so-called sick building syndrome. Synthetic materials with potential toxic pollutant emissions have been eliminated and high-quality natural materials adopted within the design to assure healthy conditions.

Variable speed gearless lifts generally use less energy than fixed speed or geared machines. Smoothing the acceleration and deceleration of the lift car for passenger comfort also reduces energy. Variable speed gearless lifts have a high power factor and produce less waste heat. Energy is used to raise cars, but their descent is assisted by gravity and this energy can be recovered in electrical power. The recovery can be approximately 30 per cent and the generated electricity used elsewhere in the building. In high-rise buildings, the use of variable speed gearless lifts with intelligent programming and energy recovery can reduce their energy consumption by as much as 50 per cent. In general, an owner-occupied building will have a greater lifting requirement than a multi-tenant building due to greater inter-floor traffic. Buildings with large inter-floor traffic patterns are complex to analyse. There are basic guidelines as to what is perceived to be acceptable in terms of waiting intervals and lift handling capacity. Experience shows that for offices waiting times of up to 25 seconds are acceptable. People show signs of initial agitation after waiting for a lift for 16–18 seconds. Most analyses assume that cars are loaded to 80 per cent. If cars are

loaded to more than 80 per cent, waiting time increases substantially. Handling capacity relates to the maximum number of passengers that a lift system can move within a five minute period. In practice, lift provision is not always optimised and is governed by economic reasons dependent on a building owner’s perception of the prestige of the property. Lifting requirements are considerably greater for tall buildings than for medium/low-rise structures. However, most office buildings of all heights have a number of lifts depending on the floor plate dimensions and the horizontaldistance that occupants are prepared to walk

Plumbing

Water use in buildings has two environmental impacts: (1) the direct use of water, a limited resource; and (2) the expenditure of energy used in water pumping, purification, treatment, and heating. Water conservation and efficiency programs have begun to lead to substantial decreases in the use of water within buildings. Water-efficient appliances and fixtures, behavioral changes, and changes in irrigation methods can reduce consumption by up to 30 percent or more. Investment in such measures can yield payback in one to three years (Gottfried 2003). Plumbing systems in tall buildings are similar to those of low-rise buildings, but the domestic water-supply systems require electric pumps and tanks to maintain pressure. If the building is very tall, it may require the system to be divided into zones, each with its own pump and tank. One early method used elevated storage tanks at the top of the building with fill pumps at the bottom of the building, a classic gravity down feed arrangement. (Dennis M. Connelly 2007) Both of these methods proved to be reliable and affordable through the years, and many such designs are still active today or still are used in current design practices.

Popular practices Efficiency equipment:

• Waterless urinals and dual-flush toilets

•The urinals are half-gallon per flush, half the usual amount

•HVAC equipment in the building does not require water for its operation.

• All sink faucets and toilets to automatic valves that use infrared technology to turn on and shut off water flows.

• Bathroom lavatory faucets use only.

• Rainwater collection for irrigating the park and cooling the building

• Supplement the water demand for the evaporative cooling towers

Cutting Edge Membrane Bioreactors

Onsite wastewater treatment is a defining characteristic of a green building, providing a sustainable source of recycled water for toilets and landscape irrigation, while also reducing occupants' demands on local potable water supplies and municipal infrastructure. More recently, membrane bioreactors (MBRs) are providing a highly compact, fully automated, low odor alternative for wastewater treatment in green buildings. These robust and reliable systems can treat both grey and black water to near drinking water quality that meets or exceeds the world's most stringent standards for water reuse. Moreover, the efficiencies in wastewater treatment and water reuse provided by an MBR can earn up to six points in LEED certification for categories that include water use reduction, water efficient landscaping, innovative wastewater treatment technologies, and innovation in design.

Electricity

About 7% of the electricity generated by power plants is lost as it's transmitted to

end users, so onsite generation is more efficient to begin with. Sustainable towers

like One Bryant Park can significantly reduce the lost. According to the architect

Robert F. Fox (Jan 2006), at, a 5.1-MW, natural-gas-fired, combined heat and power plant will generate electricity and capture the heat energy that most power plants treat as waste. The building's plant will be 77% efficient, whereas typical utility

plants are 27% efficient. Over the course of a year, on-site power generation will

meet about 70% of the building's requirements. At night, when demand drops,

electricity will be used to make ice in tanks in the cellar. During the day, ice will be

melted to supplement the air conditioning system, saving energy and evening out

daily demand. This will reduce tenants' electricity bills and protect them from the

higher "demand charge" rate that's applied to an entire month's bill if a usage

threshold is exceeded for even a moment. And cogeneration will displace power

generated by power plants that emit CO2 and other pollutants.

Lighting

Artificial light accounts for almost one-fifth of the world's electricity consumption. This is substantially more than the output of all the nuclear power stations in the world. Within 25 years, the global demand for artificial light is projected to be almost twice today’s level as the developing world moves towards western living standards. A shift in global climate trends and an international focus on sustainable energy has seen high rise buildings around the world favoring energy efficient lighting design as a means of retrofitting structures for modern times. Lighting controls are an integral component of sustainable building practices. It can also boost a project’s ability to qualify for LEED certification.

Lighting control systems play three primary roles in the LEED program. First, they are required for enabling code compliance, which is a major LEED prerequisite. Second, LEED strongly encourages designing buildings using daylight as a primary light source. Consequently, from an environmental perspective, the time and dollars spent designing and building a daylight building are wasted if lighting controls aren’t utilized for dimming or turning off electric lights when they’re not needed. Third, lighting controls can be used for further reductions of lighting energy through personal controls, and integrating the operation of lighting and mechanical systems, which are key strategies for optimizing building energy performance. Lights in tall buildings have a relatively low embedded energy cost and therefore any energy savings are real (Pank 2003). Most sustainable projects apply the lighting control into details as: Use low watt fluorescent lamps, garage lighting controls to shut off from midnight to 6 AM. Install a corridor lighting override switch, tied overhead lighting in the break areas to the emergency lighting circuit, and then set up the GE lighting relay control program with a normal daytime schedule.

Green Power

Green power refers to electricity supplied in whole or in part from renewable energy sources, such as wind and solar power, geothermal, hydropower, and various forms of biomass. Increasingly, electricity customers are being given electricity supply options, either as retail power markets open to competition or when their regulated utilities develop green pricing programs. News from US department of energy indicated that more than 40% of retail customers in the United States now have an option of purchasing green power directly from their electricity supplier. In addition, consumers can support renewable energy development through the purchase of green energy certificates. High rise structures have good opportunities to engage the green power especially with solar, wind or the purchase of Green-certified power

New York Times Tower with a solarscreen of ceramic rods.

The Solaire includes a 33kW building integrated PV system on its façade.

Solar Screen

A design guild website introduces that the south facade of a 20-storey tower block with PVs can provide enough to light most of the common areas within the building, thus more and more high rises consider solar screen as a primo on site energy source. There are three main types of photovoltaic technologies available

mono-crystalline (deep blue color),

poly-crystalline (multi-colored with sparkling blue tones) and

amorphous (black thin-film).

Mono-crystalline technology is the most efficient however it is also the most expensive.

Wind TurbineAn assessment of global wind resources (May 2002) By the European Wind Energy Association and Greenpeace concluded that the world's wind-generating potential, assuming that only 10 per cent of the earth's land area would be available for development, is double the projected world electricity demand in 2020.

The cost of wind-generated electricity has dropped from 24p a kilowatt-hour in the early 1980s to roughly 2.5pence a kilowatt-hour today on prime wind sites and is predicted to be as low as 1.3 pence by 2020 Energy balance/payback is typically two months. These devices are more suited to office buildings and high rise buildings.

A 49-storey residential tower recently proposed for Vauxhall will generate electricity from a wind turbine on the roof to power lights in communal areas. Such a technology could be deployed relatively cheaply in the future however more research has to be carried out to examine the energy production potential and where electricity. produced could be used successfully. Many designers are considering the integration of wind turbines within buildings again it is not yet known how feasible this will be. News from US department of energy indicated that the world's first integration of utility-scale wind turbines into a building has been completed in Bahrain. Atkins, a leading provider of technology-based consultancy and support services, announced.

Figure 3.37 Proposed Flower Tower by Londonarchitect Bill Dunster, Credit: Bill Dunster

Three wind turbines have been installed on the Bahrain World Trade Center, which is nearing completion.

late March that it has installed large wind turbines onto three 50-ton bridges that span the two towers of the Bahrain World Trade Center. The 50-story structure, under construction in Manama, Bahrain, is designed to channel the wind between the two towers and past the blades of the three wind turbines, which are 29 meters in diameter. According to Atkins, the wind turbines will supply up to 15 percent of the energy needs for the two towers.

A European study published in 2005 examined the potential for such building-integrated wind turbines in the United Kingdom. The study recommended further research on the wind regime in urban areas and around isolated buildings; the structural and noise implications of mounting wind turbines onto a building; and the optimal design for building-integrated wind turbines.

The report also reviewed the experience with building-integrated wind turbines. At the time of that report, the largest such project involved the installation of three 5-meter wind turbines on the roof of a building. In contrast, the wind turbines in the Bahrain World Trade Center are fully integrated into the design of the buildings. In future, the power of the whole city probably can be produced from the wind turbines integrated with high rise structures

Socio-Cultural

Impact on the city planning, local communities

The skyscraper is a necessary response to urban sprawl. Almost half of the world’s population lives in the cities, and this trend is increasing. The skyscraper has many potential economic advantages where there is minimal land use as the amount of usable space per available land area is maximized.

Because of its huge size and efficiency land use, high rise played a “big” role in city planning since Le Corbusier. The high-rise covers less land area than a low-rise development. This will provide more green areas and reduce the impact of urban sprawl on the environment. Cluster of tall buildings could cast long shade on other buildings, and strengthen the wind on the ground level. All such problems are impacting on the planning. High rises cannot be viewed in a vacuum: they exist within a specific environment and a human context. They contain their own community of residents and workers, but they are also part of the wider urban community. Herbert Girardet (February 2002) argued the urban futures of sustainable tall building should be designed for mixed use wherever possible to create balanced functions and communities. The functions of a building at ground level should contribute to the quality of the city, with shopping, eating and entertainment opportunities.

Le Corbusier is advocating with high densities, compared with the low densities.

The Malaysian architect Ken Yeang has pioneered the bio-climatic skyscraper which has been highly influential in architectural design since the 1980s. He recognizes that, due to the cultural and economic environment, tall buildings are an inevitable building form and part of the contemporary urban landscape, and he has focused on researching and developing energy-efficient and climatically-adapted buildings. The sustainability can also be improved through maximizing the utilization of the building. This can be through long hours of operation, or the provision of services, which can be shared with others –, in the same building, in the same company or in the local community (e.g. sports, conference and canteen facilities). On the other hand the users or the residence of the buildings need learn to live green as well. In Solaire, a LEED gold residential high rise, one glance at the recycling bins proved that the resident did not have the recycling system down. And the ramp leading to the Solaire's parking garage was lined with Range Rovers, Jeeps and other SUVs.

Cultural response

The skyscrapers are built for only two reasons:” to make money, responding to existing demand, or to advertise and flaunt the money one already has” Said Philip Nobel11. Nowadays we can rarely tell the location of a high rise structure 11 Philip Nobel is an author of Sixteen Acres: Architecture and the Outrageous Struggle for the Future of Ground Zero (2004) due to their similar style. Some architects even feel proud that their work can be located anywhere in the world. Obviously, tall building is not a typology to fix in with its context. It prefers to soar above, and dominate its surroundings. But that does not mean it cannot become a positive element in the urban composition. It can and should relate to its surroundings and respond to the history cultural context. Antony Wood in his “New Paradigms in High Rise Design” (2004) introduced several approaches to design help cities in their quest for an appropriate high rise expression.