Skyscraper Floor and Cladding Cost Estimator

Keith Oneil Newton

A project submitted to the faculty of Brigham Young University

in partial fulfillment of the requirements for the degree of

Master of Science

Richard J. Balling, Chair Paul W. Richards

Fernando S. Fonseca

Department of Civil and Environmental Engineering

Brigham Young University

December 2015

Copyright © 2015 Keith Oneil Newton

All Rights Reserved

ABSTRACT

Skyscraper Floor and Cladding Cost Estimator

Keith Oneil Newton

Department of Civil and Environmental Engineering BYU Master of Science

Cost estimation is vital to the success and financial viability of any construction project.

One of the greatest difficulties in the preliminary design phase of a project is providing an accurate cost estimation, and subsequently, an accurate budget. In the China Megastructures Study Abroad Program led by Dr. Richard J. Balling, the students take responsibility in performing basic cost estimation for a skyscraper design. This report describes the Skyscraper Floor and Cladding Cost Estimator (SFCCE), which is intended to (1) automate the design of a floor system given the position of megacolumns and the interior core and (2) provide a more accurate cost estimate of the floor system and exterior cladding. The SFCCE spreadsheet consists of four sheets and focuses on estimating the weight and cost of the floor system and exterior cladding. These values can then be subsequently used as inputs into a previously developed spreadsheet that performs the design and cost estimation of skyscraper belt trusses and outriggers. The SFCCE has been designed to accommodate skyscrapers with rectangular floor plans and cores. Keywords: automation, megastructures, skyscraper, cost estimation

ACKNOWLEDGEMENTS

My Masters Project was completed only through many hours of frustration and distress.

There were many times when I felt stuck and could not progress with certain ideas I wanted to

include in my project. Dr. Balling was always there to provide me with guidance and direction.

I want to express my gratitude for his hard work and patience throughout this project.

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TABLE OF CONTENTS  

LIST OF TABLES .......................................................................................................................... v 

LIST OF FIGURES ....................................................................................................................... vi 

1  Introduction ............................................................................................................................. 1 

2  Literature Review .................................................................................................................... 3 

  Automated Floor System Layout ..................................................................................... 3 

  Cost Estimation. ............................................................................................................... 6 

  Difficulties with High-Rise Cost Estimation ................................................................. 10 

3  The Cost Estimation Spreadsheet (SFCCE) .......................................................................... 11 

  Floor System Tab ........................................................................................................... 11 

3.1.1  Inputs....................................................................................................................... 12 

3.1.2  Outputs .................................................................................................................... 12 

  Cladding Tab .................................................................................................................. 17 

3.2.1  Inputs....................................................................................................................... 17 

3.2.2  Output ..................................................................................................................... 17 

  Additional Tabs .............................................................................................................. 20 

4  Assumptions and Limitations ................................................................................................ 21 

  Assumptions ................................................................................................................... 21 

  Limitations ..................................................................................................................... 22 

  Future Improvements ..................................................................................................... 25 

5  Conclusions ........................................................................................................................... 27 

References ..................................................................................................................................... 29 

v

LIST OF TABLES

Table 1: Structural Design of Buildings (Nimtawat 2009) ............................................................. 3

Table 2: Building Efficiency (Langdon) ......................................................................................... 7

Table 3: Height Charge (Gossow 2000) ....................................................................................... 10

Table 4: Approximate Time of Construction ................................................................................ 15

Table 5: Weekly Crane Costs and Crane Capacity ....................................................................... 15

Table 6: Architectural Cladding Properties .................................................................................. 18

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LIST OF FIGURES

Figure 1: Typical Evolution of Solutions (Nimtawat 2009) ........................................................... 5

Figure 2: Increase of Building Costs in Relation to Height

and Size of Floor Plan (Van Oss 2007) ........................................................................... 8

Figure 3: Increase of Building Costs (de Jong 2008) ..................................................................... 9

Figure 4: Increase of Costs Due to Height (Van Oss 2007) ........................................................... 9

Figure 5: SFCCE Cell Color Legend ............................................................................................ 11

Figure 2-6: Screenshot of the Floor System Tab .......................................................................... 16

Figure 2-7: Screenshot of the Cladding Tab ................................................................................. 19

Figure 2-8: Screenshot of the Constants Tab ................................................................................ 20

Figure 2-9: Floor System of the “Guangzhou Group” .................................................................. 23

Figure 2-10: Floor System of the “Hong Kong Group” ............................................................... 24

Figure 2-11: Floor System of the “Shenzhen Group” ................................................................... 24

Figure 2-12: Floor System of the “Beijing Group” ...................................................................... 25

1

1 INTRODUCTION

The China Megastructures Study Abroad Program course offers students valuable design

and research experience of tall buildings. During the course, the students are divided into groups

and share responsibility for a culminating skyscraper design project. The students not only

design the architectural and structural elements of a skyscraper, they are also required to perform

basic cost estimation for their design. The manner in which cost estimation was carried out has

evolved significantly since the initial commencement of the course. At first, skyscraper cost was

estimated simply based on the average cost per square footage of the geographic location of the

building site. Cost estimation became a more involved procedure in subsequent years, leading to

the Skyscraper Floor and Cladding Cost Estimator (SFCCE).

The SFCCE spreadsheet acts as a predecessor to the “5ex_Skyscraper_Formulas.xlsm”

spreadsheet previously developed by Dr. Richard J. Balling which assumes a value for the floor

and cladding weight. The purpose of the SFCCE spreadsheet is to obtain more accurate and

design specific weight values for the floor system and exterior cladding. The spreadsheet

automatically designs the floor slab and support beams in order to calculate the floor weight and

uses the building geometry to calculate the cladding weight. Costs are estimated based upon

material, labor, transportation, and equipment and craning costs.

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3

2 LITERATURE REVIEW

Automated Floor System Layout

Any process that involves iteration and discernible patterns can, at least to a certain

extent, be automated. Optimizing a floor system is no different, and many studies indicate the

potential benefit for developing programs to streamline such tasks. Complicated automations

require the use of artificial intelligence (AI) to develop solutions. There are many subdivisions

that fit under the umbrella of AI including knowledge-based expert systems (KBES), case-based

reasoning (CBR), and genetic algorithms (GA) (Nimtawat 2009). Computer automation in

structural design is more valuable where more experiential data can be employed by the program

to produce optimal results. Table 1 shows various tasks of the structural design process, their

corresponding process characteristics, and the principal role of both the computer and the

engineer.

Table 1: Structural Design of Buildings (Nimtawat 2009)

4

Under the conceptual design stage, many design programs select the most appropriate

structural system for a particular building and also provide the basic architectural layout. A

program called HI-RISE, for example, uses KBES for the conceptual and preliminary design

phases of rectangular-shaped skyscrapers (Maher 1984). Many other programs exist that use

either KBES, CBR or GA to assist engineers with design (Nimtawat 2009).

The preliminary design stage focuses on establishing a layout of the structural members

in the system as well as the analysis of the members. There have been many attempts to automate

beam-slab layout design. Programs seek to create these layouts under basic design criterion. For

example, a system proposed by Tsakalis weighed in on mainly architectural and financial data to

form a design solution (Tsakalis 1994). Another program used by Syrmakezis, MAKE,

generated multiple beam-slab options for the floor system, which can then be selected by the user

(Syrmakezis 1996). Most of these programs are currently limited to rectangular floor plans of

high-rise buildings that use a uniform design throughout each story. These programs listed above

all rely on KBES, which also comes with its own limitations. The IF-THEN structure of the

program used to determine a solution do not encompass all possible solutions and their search

space has tighter bounds (Nimtawat 2009).

A different approach to floor system design, created by Bailey and Smith, uses a CBR

program coupled with CAD (Bailey 1994). The geometric models and topological data of

existing buildings can be utilized by the program to form solutions for new designs. The

weakness of CBR is that requires a generous amounts of previous design cases, but also a

complicated routine for acclimating the old design to the new one as a solution (Nimtawat 2009).

GA programs are capable of finding useful solutions in large search areas, and

subsequently, have become a more common technique to use for structural design automation. A

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study by Anan Nimtawat and Pruettha Nanakorn focused on the automation of beam-slab floor

systems using a GA approach (Nimtawat 2009). In order for this to be accomplished, all gridline

positions connected columns had to be mapped out in binary. The beam-slab layout is described

by a chromosome string which is subject through multiple crossover and mutation processes.

Infeasible solutions were penalized. The code also placed a bias on layouts with fewer beam

segments and larger slab areas and there is a maximum allowable length placed on the slab

(Nimtawat 2009). The study examined how quickly the floor system converged upon a solution

when the population size was variable. The higher the population size, the less generations that

were required to come to a solution. Figure 1 shows the typical evolution of a beam system at

different generations.

Figure 1: Typical Evolution of Solutions (Nimtawat 2009)

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The code was run on actual floor plans so that the calculated floor design could be

compared to the actual. The layouts provided by the code were found to be realistic solutions in

each applied case. Additional beam-slab problems were studied and tested by Nimtawat and

Nanakorn to further assess the usefulness of their code (Nimtawat 2010). The study concluded

that practical beam-slab layout designs can be produced through automation with the given

positions of columns and walls.

In a more recent study conducted by Eugenio Rodrigues, a similar GA approach is used

to automate floor systems. The algorithm expands upon this idea and attempts to incorporate

more design preferences from the architect such as maximum areas, space usage, multiple

stories, and overhangs. The study acknowledges that not all preferences can be quantified, and

the automation should serve as a guide and helper to the architect or engineer (Rodrigues 2014).

Cost Estimation.

Cost estimation is vital to the success and financial viability of any construction project.

One of the greatest difficulties in the preliminary design phase of a project is providing an

accurate cost estimation, and subsequently, an accurate budget. A project can quickly go over

budget if a cost estimate is too optimistic, but a contract bid can be lost if the estimate is too

conservative.

One of the most critical aspects of cost estimation is data collection. Cost models are

developed and built based off of previously completed projects (Heemstra 1992). Unfortunately,

this means that a suitable number of projects must already be constructed to develop an accurate

assessment of the costs. Depending on the building site, there is limited data to pull from and

make empirical comparisons. There are also numerous factors that influence cost; many of which

are difficult to include in cost models.

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A recent study performed by Peter de Jong and Sanders van Oss indicates the tremendous

level of complexity that develops with the creation of cost models used to accurately portray

high-rise buildings (Van Oss 2007). The study was performed in the Netherlands, but its

findings are universally applicable although costs will differ slightly based upon area.

Building costs correlate with the gross floor area (GFA), while revenues correlate with a

building’s lettable area (LA). When designing a high-rise, building efficiency is important in

determining the practicality of such a project and is defined by the ratio of LA/GFA. Table 2

shows typical building efficiency ranges of buildings at varying number of floors.

Table 2: Building Efficiency (Langdon 2002)

Increased verticality is associated with a drop-off in building efficiency. One reason behind this

decrease of efficiency is the requirement for elevators. In high-rises, elevators can take up to

about 5% of the GFA. Building efficiency can improve by optimizing the dimensions of the

floor slab, structural columns, and the interior core (Sev 2008). Figure 2 compares both number

of floors and GFA per floor to cost.

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Figure 2: Increase of Building Costs in Relation to Height

and Size of Floor Plan (Van Oss 2007)

The figure suggests that the most inefficient designs are those with a high number of stories but a

low GFA. This should be intuitive as the requirement for vertical transport does not change, but

the capacity for lettable area decreases.

It was concluded that building costs increase about 8% every ten floors (Van Oss 2007).

This can fluctuate slightly based upon location and time frame. The cost increase stems mainly

from the structural elements and the additional elevators. Figure 3 and Figure 4 illustrate the

increased costs among various components of the building as the number of stories increase.

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Figure 3: Increase of Building Costs (de Jong 2008)

Figure 4: Increase of Costs Due to Height (Van Oss 2007)

The figures above confirm that the main cost increases originate from the structural and elevator

requirements. It should also be noted that the foundation is one of the least affected components

in relation to the number of stories.

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Difficulties with High-Rise Cost Estimation

Several costs that are associated with high rises are typically not accounted for in these

cost models. For example, there are greater requirements for a tall building’s plant and

distribution system, and the ability to supply adequate pressure up through the higher vertical

distances is increasingly cumbersome. The extra wind loading inevitably leads to heavier frames.

The movement of materials and the use of labor can be more difficult as well. There are also

amplified risks attached to large buildings with regards to enhanced safety measures and liability

concerns (de Jong 2008).

The credibility of any cost model generally stems from historical data that can be

compared easily based upon location, floor size, and other similar characteristics. The problem

with high-rise buildings is that there is a limited pool of data to use for an accurate cost

comparison. Cost models attempt to rectify these additional costs by implementing a “height

charge” factor to account for the more elaborate costs as shown in Table 3 (de Jong 2008).

Table 3: Height Charge (Gossow 2000)

These factors, however, are subjectively placed. One problem associated with using these height

factors is that some elements in a building are affected by the larger heights dramatically, while

others are not affected at all.

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3 THE COST ESTIMATION SPREADSHEET (SFCCE)

This spreadsheet consists of four tabs: Floor System, Cladding, Constants, and W-Shapes.

The first two tabs require user input before any calculations can be performed. The spreadsheet

outputs include the weight and cost of the floor system and cladding as well as a graphical

representation of the floor system layout. The spreadsheet is formatted to be user-friendly, and

the cells designating inputs and outputs are color coded as indicated by Figure 5. The latter two

tabs of the spreadsheet store material properties and unit cost values which are referenced in

several of the calculations.

Figure 5: SFCCE Cell Color Legend

Floor System Tab

A screenshot of this tab, Figure 2-6, is provided at the end of the section. The figure

designates a number of inputs (shown in red) and outputs (shown in green), which are discussed

in greater detail in the following subsections.

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3.1.1 Inputs

The first user input indicates the number of megacolumns in the structure (a). Once a

number has been entered, the corresponding number of rows for the ‘x’ and ‘y’ coordinate nodes

automatically appears (b). The user can then enter the coordinates of each megacolumn, bearing

in mind that the coordinates must be input in a sequential counter-clockwise order and form a

rectangular area in order for the building layout to be graphed correctly and the calculations to be

valid. The length and width of the concrete core are also input by the user (c).

The user may also input the type of occupancy to modify live loads (d). Currently, the

spreadsheet allows for residential, office, school, retail, and restaurant live loads. If other loads

types are desired, they can be manually added to the data validation table.

The last user input is the approximate number of miles away from the nearest

manufacturing plant (e). This information is used to calculate the transportation costs of all of

the materials.

3.1.2 Outputs

After the user fills out all the necessary inputs, the spreadsheet performs several

calculations and calculates the floor live load (a), floor dead load (d), and total floor cost (c).

However, the dead load cannot be adequately estimated until the floor slab and the structural

members supporting the floor slab are designed. Therefore, one of the first tasks accomplishes is

to design and graph the floor system (b).

Floor Live Load 

The floor live load is the simplest output to determine. After the user selects the type of

floor occupancy, the corresponding live load appears.

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Floor System Graph 

Once the user inputs the number of megacolumns and the corresponding nodal coordinates,

they are automatically added as data points on the graph. The megacore is also included based

upon the user-defined dimensions. The starting and ending coordinates for each beam are then

determined. The girder beams have a starting node at each megacolumn and an end node at the

closest point on the megacore. The perimeter beams span from megacolumn to megacolumn, and

the intermediate beams span along the girders at an equal spacing to make sure that the slab does

not span more than twenty feet. There are a maximum of three intermediate beams that will act

as point loads on the girders. If more intermediate beams are required, an error message appears

explaining that the analysis cannot be performed with the current inputs.

Floor Dead Load 

Once the nodes of each beam in the system are determined, their associated lengths are

calculated by the distance formula. They are then analyzed as simply supported members. The

perimeter and intermediate beams are stressed with uniform live and dead loads acting on the

slab while the girder beams are stressed with the point loads from each of the intermediate beams

in the floor system. Once the reactions and moments are calculated, the spreadsheet optimizes

beam shapes with a simple loop in Visual Basic to ensure that the provided elastic section

modulus ‘S’ of a given shape is larger than the required elastic section modulus calculated by the

formula below.

14

Where = Allowable bending moment stress = 30 ksi

M = Bending moment in steel member

= Elastic section modulus

1

The spreadsheet uses the Allowable Strength Design (ASD) instead of Load Reduction

Factor Design (LRFD) in order to be consistent with the values provided in the constants tab.

After the beam shapes are optimized in the floor system, the total steel weight and cost can then

be calculated.

Total Floor Cost 

The total cost is the calculated sum of material, labor, transportation, and equipment and

craning costs. The material costs are calculated by using the total weight of steel and concrete

and multiplying by their corresponding unit material cost. Labor costs are influenced by a

significant number of factors, which typically range from 30% - 40% of the material costs. The

spreadsheet assumes a conservative value of 40% of the total concrete and steel cost for labor. A

constant value of 6 cents per ton per mile is used as an estimate for shipping costs. The total

transportation costs are then determined by using the total weight, the total shipping distance,

and the cost per ton per mile.

The equipment and craning costs are influenced by both the total floor area and the

number of stories. The first step of approximating the equipment and craning costs is to estimate

the time of construction. The spreadsheet calculation uses simple ratios between the user defined

floor area and that of the Pearl River Tower in Guangzhou, China. Similarly, it uses a ratio for

15

the number of stories (input on the Cladding Tab). These ratios are then used to approximate the

number of weeks of construction as indicated in Table 4. Once a timetable is established, the

appropriate number of cranes to procure to complete construction is estimated. Table 5 shows the

approximate cost of operation per week of several different crane sizes and is derived from an

existing table from C&S Crane & Rigging Inc. The table also indicates the allowable lift capacity

of each crane at a specified radius with 25 ft., 50 ft., and 100 ft. options. The spreadsheet takes

into account the tonnage of the floor system and the floor area to approximate the number of

cranes. The number of cranes required can then be multiplied by the weekly operation rate to

estimate the equipment and craning costs.

Table 4: Approximate Time of Construction

Table 5: Weekly Crane Costs and Crane Capacity

16

Figure 2-6: Screenshot of the Floor System Tab

17

Cladding Tab

A screenshot of this tab, Figure 2-7, is provided at the end of the section. The figure

designates a number of inputs (shown in red) and outputs (shown in green), which are discussed

in greater detail in the following subsections.

3.2.1 Inputs

The first few inputs on this tab are the story height and the number of stories (a). These

parameters, along with the floor system dimensions input from the previous tab are used to

calculate the total surface area of the building (a). Although the total surface area is calculated

by default, it is delineated as an input because the value may be overridden by the user. In such

cases, the user may opt to use the surface area pulled from the skyscraper model if more complex

geometry is to be accounted for such as tapered buildings.

The user also has the ability to choose between three typical architectural cladding

panels: precast concrete, glass fiber reinforced concrete (GFRC), and thinshell (b). The

percentage between concrete cladding panels and exterior glass curtain walls can also be input by

the user (c).

Again, the last user input is the approximate number of miles away from the nearest

manufacturing plant (d). This information is used to calculate the transportation costs of all of

the materials.

3.2.2 Output

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The cladding tab has two main outputs: the dead load (b), and total floor cost (a).

A list of the cladding options and their associated properties, courtesy of Willis Construction Co.

Inc., is provided in Table 6. This table is used to calculate the desired outputs.

Table 6: Architectural Cladding Properties

Dead Load 

The weight of the selected cladding option (in psf) is multiplied by the total surface area

to determine the dead load. This value was found to be quite close to the estimated value in Dr.

Balling’s “5ex_Skyscraper_Formulas.xlsm” spreadsheet when architectural precast cladding was

selected. The other options, because they are much lighter, reduce the total dead weight

substantially.

Total Floor Cost 

The total cost is the calculated sum of material, labor, transportation, and equipment and

craning costs. The labor and material cost are analogous to the weight calculation and are

determined by multiplying the cost (in psf) by the total surface area. Calculating the

transportation costs is the same as the calculations for the floor system. A constant value of 6

cents per ton per mile is used as an estimate for shipping costs. The total transportation costs are

then determined by using the total weight, the total shipping distance, and the cost per ton per

mile. The equipment and craning costs for cladding are based off of a simple linear interpolation

of story heights and corresponding craning costs; with user input between 8 and 120 stories, it

determines a value between $800/ton and $1300/ton.

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Figure 2-7: Screenshot of the Cladding Tab

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Additional Tabs

The constants tab is pulled directly from the “5ex_Skyscraper_Formulas.xlsm”

spreadsheet. This tab contains the relevant properties and cost values for concrete and steel that

are used in the floor system and cladding calculations. The W-Shapes tab is essentially an

abridgment of the AISC database; it includes W36 shapes or smaller while excluding shapes that

are slender in bending. See Figure 2-8 for a screenshot of this tab.

Figure 2-8: Screenshot of the Constants Tab

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4 ASSUMPTIONS AND LIMITATIONS

Assumptions

The spreadsheet makes several assumptions that are acknowledged and addressed in this

section. The first key assumption was that the deflection of a beam would not control the design

due to the rigidity of the floor slab. Under this assumption, deflection calculations were not

required or performed. Subsequently, bending moment was the governing stress for beam design

in the floor system.

Each beam was modeled as a simply supported member, an assumption used to simplify

calculations. The steel members in a megastructure, however, will typically employ fixed

connections. For example, the wide-flange spandrel beams of the Pearl River Tower are

connected to the exterior columns at each floor to form moment frames for the lateral force

resisting system of the structure (Tomlinson 2014).

The max span of a 10 inch floor slab was assumed to be 20 feet. The spreadsheet does not

allow for dynamic input on the thickness of the slab, nor does it calculate the necessary amount

of reinforcement to include in the slab.

The girder beams in the spreadsheet were modeled with point loads from the intermediate

beams. The point loads were assumed to be significantly larger than the weight of the girders

themselves; therefore, the self-weight was neglected in the moment calculations. Superposition

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of both the point loads and the uniform self-weight load could have been employed to be more

precise in determining the beam shapes.

There are two section modulus properties: the elastic section modulus (S) and the plastic

section modulus (Z). The former is used for materials up to the yield point; the latter is used for

materials after elastic yielding has occurred up until the formation of a plastic hinge. This

spreadsheet assumes structural failure of a member once any yielding has occurred and compares

the allowable elastic section modulus with the required. If the plastic section modulus was used

instead, the beams would have a higher capacity and smaller shapes could be used in the analysis

of the floor system.

Limitations

Although the spreadsheet makes great strides towards finding more precise weights and

costs, it is not without its flaws and limitations. The spreadsheet is only applicable to skyscrapers

with rectangular floor systems and rectangular cores. This proved to be one of the most

significant drawbacks. Groups in the most recent China Megastructures study abroad program,

had many unique designs which the spreadsheet was incapable of. As shown in Figure 2-9,

Figure 2-10, and Figure 2-11, the floor systems for each group were comprised of various shapes

that were incompatible with the current functionality of the spreadsheet. These floor systems

had to be manually graphed and evaluated, indicating the need for a much more general graphing

function that can support various shapes. It was evident that the concrete core would also need to

support multiple shapes.

The spreadsheet also restricts the quantity of megacolumns to a maximum number of

twenty. This seemed like a reasonable cap in the initial setup of the spreadsheet; yet, it still

23

presented an obstacle for one of the groups as shown in Figure 2-12. The floor system in

question had a rectangular shaped floor plan and a rectangular core, but it also had 24

megacolumns along its perimeter. There were not enough nodes available to automatically

design the floor system. The limitations of the spreadsheet were considerably more apparent as

the spreadsheet continued to develop.

The spreadsheet relied on Visual Basic coding to optimize the steel shapes used in the floor

system. The code requires going back and forth between both Visual Basic and Excel programs

through multiple iterations and causes a slight lag time. If the calculations were designed

entirely in one program, the results would be produced much quicker.

Figure 2-9: Floor System of the “Guangzhou Group”

24

Figure 2-10: Floor System of the “Hong Kong Group”

Figure 2-11: Floor System of the “Shenzhen Group”

25

Figure 2-12: Floor System of the “Beijing Group”

Future Improvements

The most significant improvement of the spreadsheet would enable the user to input node

coordinates for megacolumns without restrictions on the shape of the floor system or the

concrete core.

The Visual Basic for Applications (VBA) code runs much slower than originally

anticipated. The existing code requires storing variables from excel, running an iteration, and

then rewriting the new variables into Excel. This process introduces a substantial amount of lag

associated with performing multiple iterations but can be effectively nullified if the W-shape

database was stored in VBA as an array and all required calculations were executed directly from

the code. Only the final results would be written in Excel.

The original assumption that deflection would not govern became very questionable as

the project developed. It simplified calculations, but with such large spans, deflection checks

26

would certainly be required to produce sensible results. It would also be beneficial in future

versions to indicate which failure criterion governs for each beam: deflection or bending

moment.

The slab thickness, in future versions, should act as a dynamic input. The design thickness

was set to ten inches, with a constant maximum span of twenty feet. This leads to a

tremendously heavy floor design that is overly conservative. It would be far more beneficial for

the user to input a desired thickness, which can be linked to a corresponding maximum span.

27

5 CONCLUSIONS

The SFCCE spreadsheet acts as a predecessor to the “5ex_Skyscraper_Formulas.xlsm”

and can be a valuable tool to provide a preliminary cost estimate for both the floor system and

the exterior cladding of a high-rise structure. The spreadsheet automates the initial design of the

concrete slab and optimizes beam shapes according to ASD loading. The total steel and concrete

material used in the floor system is calculated and the average weight (in force/area) is provided

as an output. In addition to material costs, the spreadsheet incorporates transportation, labor, and

equipment and craning costs. Although the spreadsheet produces reasonable results; it is not

without its limitations. The spreadsheet is capable of evaluating only rectangular shaped floor

plans with rectangular cores. This weakness in the spreadsheet means that a vast number of

possible skyscraper designs are incapable of being analyzed. There is an inherent need to

improve upon the existing spreadsheet to include any floor-print, regardless of the complexity of

shape.

28

29

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