SELECTION OF STRUCTURAL SYSTEMS AND MATERIALS:

MINIMIZING LATERAL DRIFT AND COST OF TALL BUILDINGS

IN SAUDI ARABIA

by

Othman Subhi AlShamrani

A Thesis Presented to the FACULTY OF THE SCHOOL OF ARCHITECTURE

UNIVERSITY OF SOUTHERN CALIFORNIA In Partial of Fulfillment of the Requirements for the Degree

MASTER OF BUILDING SCIENCE

May 2007

Copyright 2007 Othman Subhi AlShamrani

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Acknowledgments

First of all, I am very grateful to God who granted me with a lot of help and support to

achieve my goal and gave me the opportunity to complete my higher education in the

United States, without him I wouldve not been able to do it. Second, I thank my parents,

Subhi Daifullah and Rahmah Mohammed, for their great support and encouragement

throughout my education. They have been providing me with all the needs and cared

more than what I expected. I thank them for their best advices, concerns, and their

prayers for me.

I would like to express special gratitude to my advisor and committee chair professor G

Goetz Schierle. Professor Schierle provided me with guidance and advices that enabled

me to achieve my degree. His efforts, suggestions, and prompt respond are the reasons

that ease to maintain the standard of scholarship that this thesis required. I would as well

thank him for his valuable book which was the one of the most useful source for my

thesis.

I would like to thank my committee members: Professor Doug Noble, the associate dean

who gave me a lot from his precious time and guided me to narrow dawn my thesis. I

really appreciate his effort and instructions. He taught me to manage my work with the

time. I really thank the expert person Mr. Dimitry Vergun for his advices and abundant

information that helped me to accommodate my test with the real works in the consulting

offices. Also, I am grateful to Professor Thomas Spiegelhalter for his guidance,

encouragements, and his valuable advices about some books. I would also like to thank

Dr. Mohammed AlSatari for providing me with very useful information in the field of

civil and structural engineering. I really appreciate his efforts, guidance, tolerance and

patience. I would also like to give special acknowledgement for Professor Marc Schiler

the Director of Master of Building Science Program. Professor Schiler taught me a lot,

encouraged me to publish paper, and revised my thesis.

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I am grateful to the Government of Saudi Arabia as well as King Faisal University for

providing me with all the financial needs that kept me worry free during my studies.

Many individuals have provided support, advices, and encouragement to me in the

completion of this dissertation. I am grateful to Dr. Rashed Alshaali for assisting me to

stable my life in Los Angels as well as giving me valuable advices to accomplish my aim

easily. I would like to thank my friend, Merzak Toubal, for his assistance with ideas. I

would also like to express gratitude to my undergraduate Instructor Dr. Turki ALQahtani

for his advices and guidance to join the University of Southern California to earn my

master degree. I would also like to thank my undergraduate professors, Mohammed

ALNuman, Abdullah Albashir, Ahmed Almusallami, Khaled AlMaddlah, Mansor

AlJadid, Ibrahim Almofeez, Hashim AlSaleh, Ahmed Alrwashid, Faris Alfaraidhy,

AbdulAziz AlHamad, Ali AlQarni, AbdulAziz AlGhonaimi, Mahammed Imttar, and

Mohammed Foad for their tolerance, patience and care. I also thank my friend Engineer

Montasir ALMasaud for helping me to apply to the American Universities. I would also

thank his brother Dr. Mohammed AlMasaud the Dean of the College of Architecture in

King Faisal University for approving my scholarship. I will not forget to thank Dr. Saeed

AlOmar for his valuable advices and guidance.

Special thanks to my relatives, Hawash Daifullah, Ali Subhi, Saeed Subhi, Hailmah

Subhi, AbdulKareem Subhi, Ishah Subhi, Khadijah Subhi, Moaad Subhi, Mosa Subhi,

Mohammed Daifullah, Talal Hamdan, Ali Daifullah, Saeed Daifullah, Amer Ali, Ahmed

Hawash, Mohammed Ali, Tareq Mohammed, Abdulraheem Ali, Abdulrhman Abdullah,

and Ibrahim Mohammed for their concerns and questions.

Finally, many warm thanks for her and just for her, my wife the mother of my precious

sons Sultan and Salman for her daily care and concern. Mona Masfer AlShamrani the one

who encouraged and assisted me to achieve my goals. I really appreciate her concern,

struggle, tolerance, patience, and love.

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TABLE OF CONTENTS Acknowledgments...ii List of Tables.......ix List of Figures.... xiv Abstract...........................................................................................................................xxii Chapter 1. Introduction

1.1. Introduction 1 1.2. Objective and Scope of Study 1 1.3. Selection Steps 1 1.4. Structural Systems and Materials 2 1.5. Selection of Structural Systems.. 4 1.6. Selection Criteria 5 1.7. Tall Buildings in Saudi Arabia. 5 1.8. Wind Load Considerations... 7

Chapter 2. Research Methodology 2.1. Introduction. 8 2.2. Data Collection Methods 8 2.3. Thesis Tools and Testing Model. 8 2.3.1. Testing Model. 8 2.3.2. STAAD Pro 2005 Software 9 2.4. Design Methods.. 10 2.5. Data Analysis Method.12 2.5.1. Selection of Structural System Method.. 12 2.5.2. Drift Measuring Method. 13

Chapter 3. Selection of Structural System Criteria 3.1. Introduction. 15 3.2. Proposed General Criteria List 16 3.3. Case Study Selection Process... 18 3.4. Structural Criteria. 19 3.4.1. Material Cost 19 3.4.2. Labor Cost 19 3.4.3. Integration and Synergy 20 3.4.4. Ease of Construction 20 3.4.5. Span Limits.. 21 3.4.6. Gravity Load 24 3.4.7. Seismic Load 25 3.4.8. Noise Control 27

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3.4.9. Fire Safety 28 3.4.10. Sustainability (durability and recyclable). 28 3.4.11. Strength, Stiffness, Stability, and Synergy 29 3.4.12. Corrosion and Moisture Resistance.. 30 3.4.13. Material Transportation 30 3.4.14. Environmental Impact and Energy Consumption... 31 3.4.15. Low Maintenance Cost 32 3.4.16. Design Possibility... 32 3.4.17. Material Availability... 33 3.4.18. Building Type. 34 3.4.19. Building Location.. 34 3.4.20. Building Height Limit 34 3.4.21. Code Requirements 35 3.4.22. Site Conditions (Access and Storage) 36 3.4.23. Technology Availability. 36 3.4.24. Energy Efficiency and Thermal Mass 37 3.4.25. Soil Class 38 3.4.26. Healthy Living & Indoor Air Quality. 39 3.4.27. Morphology 39 3.4.28. Weather and Climate Condition. 40 3.4.29. Security.. 40 3.4.30. Exterior Cladding... 41 3.4.31. Minimal Story Height. 41 3.4.32. Cash Flow and Financing Costs. 42 3.4.33. Building Configuration... 42 3.4.34. Future Modification 42

Chapter 4. Background

4.1. Introduction. 43 4.2. Wind Force.. 43 4.2.1. Wind Situations... 44 4.2.2. Correlation of Wind Speed and Pressure. 44 4.2.3. General Wind Effects. 44 4.2.3.1. Direct Positive Pressure.. 45 4.2.3.2. Aerodynamic Drag. 45 4.2.3.3. Negative Pressure (Suction)... 45 4.2.3.4. Rocking Effects.. 46 4.2.3.5. Harmonic Effects... 46 4.2.3.6. Clean Off Effect. 46 4.2.4. Critical Wind Effects on Buildings. 47 4.2.4.1. Inward Pressure on Exterior Wall... 47 4.2.4.2. Overturn Effect... 48 4.2.4.3. Shear Force 48 4.2.4.4. Pressure on Roof Surfaces.. 48 4.2.4.5. Torsional Effect.. 49

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4.2.4.6. Dynamic Effects. 49 4.2.5. Code Requirements for Wind. 49 4.2.5.1. Basic Wind Speed in Saudi Arabia. 50 4.2.5.2. Design Wind... 51 4.2.5.3. Wind Pressure Calculation Example.. 54 4.2.6. Special Requirements 55 4.2.6.1 Overturning Moment. 55 4.2.6.2. Torsion.. 55 4.3. Lateral Drift... 55 4.3.1. Drift Definition. 55 4.3.2. Code Requirements for Drift. 57 4.3.3. Drift Effect 57 4.3.3.1. Height to Width Ratios.. 58 4.3.3.2. Span of Girders.. 58 4.3.3.3. Member Size of Frame..58 4.4. Lateral Force Resistance Structural Systems........................................... 59 4.4.1. Moment Frame..........................................................................................59 4.4.1.2. Lateral Drift of Moment Frame............................................................... 61 4.4.2. Braced Frame 62 4.4.2.2. Lateral Drift of Braced Frame.................................................................. 63 4.4.3. Shear Walls64 4.4.3.2. Lateral Drift of Shear Wall....................................................................... 67 4.5. Structural Systems Comparisons... 68 4.6. Allowable Stress Design 69 4.6.1. Allowable Stress Definition... 69 4.6.2. Allowable Stresses for Different Materials 70 4.6.2.1. Allowable Stresses for Wood 70 4.6.2.2. Allowable Stresses for Steel.. 70 4.6.2.3. Allowable Stresses for Masonry 71 4.6.2.4. Allowable Stresses for Concrete 71 4.6.3. Steel Buckling... 72 4.6.4. Slenderness Ratio.. 73 4.7. Previous Studies (Lateral Drift Caused by Wind Forces).. 74

Chapter 5. Data Analysis 5.1. Introduction. 76 5.2. Simulation Assumptions. 76 5.2.1. Lateral Loads.. 76 5.2.2. Allowable Stresses 77 5.2.3. Framing Schemes 77 5.2.4. Cost Estimate.. 77 5.2.4.1. Steel Cost 77 5.2.4.2. Concrete Cost... 78 5.3. 10 Story Building. 78

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5.3.1. Loads for 10 Story Building 78 5.3.2. Combined Axial + Bending Stress for 10 Story Building... 81 5.3.3. Member Sizes for a 10 Story Building 82 5.3.3.1. 10 Story Steel Moment Frame. 82 5.3.3.2. 10 Story Concrete Moment Frame... 83 5.3.3.3. 10 Story Steel Braced Frame... 84 5.3.3.4. 10 Story Concrete Shear Wall. 85 5.3.4. Cost for a 10 Story Building 86 5.4. 20 Story Building. 87 5.4.1. Load for 20 Story Building.. 87 5.4.2. Combined Stress for 20 Story Building... 88 5.4.3. Member Sizes for a 20 Story Building 89 5.4.3.1. 20 Story Steel Moment Frame. 89 5.4.3.2. 20 Story Concrete Moment Frame... 90 5.4.3.3. 20 Story Steel Braced Frame... 91 5.4.3.4. 20 Story Concrete Shear Wall.. 92 5.4.4. Cost for a 20 Story Building 93 5.5. 30 Story Building. 94 5.5.1. Load of 30 Story Building... 94 5.5.2. Combined Stresses for a 30 Story Building. 95 5.5.3. Member Sizes for a 30 Story Building 96 5.5.3.1. 30 Story Steel Moment Frame. 96 5.5.3.2. 30 Story Concrete Moment Frame... 97 5.5.3.3. 30 Story Steel Braced Frame... 98 5.5.3.4. 30 Story Concrete Shear Wall.. 99 5.5.4. Cost of 30 Story Building 100 5.6. 40 Story Building. 101 5.6.1. Load for 40 Story Building.. 102 5.6.2. Combined Stresses for a 40 Story Building. 102 5.6.3. Member Sizes for a 40 story Building. 103 5.6.3.1. 40 Story Steel Moment Frame. 103 5.6.3.2. 40 Story Concrete Moment Frame... 104 5.6.3.3. 40 Story Steel Braced Frame... 105 5.6.3.4. 40 Story Concrete Shear Wall.. 107 5.6.4. Cost for 40 Story Building... 108 5.6.5. Total Cost Comparisons... 109

Chapter 6. Simulations Results 6.1. Introduction. 110

6.2. Lateral Drift 110 6.2.1. Lateral Drift of 10 Story Building.. 110 6.2.2. Lateral Drift of 20 Story Building.. 113 6.2.3. Lateral Drift of 30 Story Building.. 116 6.2.4. Lateral Drift of 40 Story Building.. 119 6.2.5. Lateral Drift up to 40 Story Building.. 121

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6.3. Labor and Material Cost. 124 6.3.1. Cost of 10 Story Building... 124 6.3.2. Cost of 20 Story Building... 126 6.3.3. Cost of 30 Story Building........................................... 128 6.3.4. Cost of 40 Story Building... 130 6.3.5. Total Cost up to 40 Story Building. 132 6.4. Material Quantities..134

Chapter 7. Conclusions and Recommendations 7.1. Conclusions. 137 7.2. Recommendations... 140

Bibliography... 141 Appendices Appendix A. Structural Floor Framing Systems Comparisons

A.1. One - Way Solid Slab. 144 A.2. Two - Way Solid Slab 145 A.3. Two - Way Flat Slab.. 146 A.4. Two - Way Flat Plate Slab. 147 A.5. One - Way Joist Slab.. 148 A.6. Two - Way Joist (waffle) Slab 149

Appendix B. Vertical Structural Systems Comparisons

B.1. Moment Frame System... 150 B.2. Diagonal Braced Frame System.. 151 B.3. Shear Walls System. 152 B.4. Shear Walls and Frame System... 153 B.5. Tube System 154 B.6. Framed Tube System... 155 B.7. Staggered Truss System.. 156

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List of Tables

Table 2.1: Combined Axial and Bending Stresses for 20 Story Concrete Moment Frame.................. 10 Table 2.2: Combined Axial and Bending Stresses for 20-Story Steel Moment Frame.................. 11 Table 2.3: Allowable Axial Loads in Kips for Wide Flange (W14)............... 12 Table 2.4: Measuring the maximum Actual Lateral Drift (Deflection).................. 14 Table 3.1: Environmental Impact of Reinforced Concrete and Steel beams................. 32 Table 3.2: Soil Types and Capacity................... 38

Table 4.1: Basic Wind Speed and Pressure.................. 50

Table 4.2: Structural Systems Comparisons..................... 68 Table 4.3: Allowable Stress for Wood.................. 70 Table 4.4: Allowable Stress for Steel................ 70 Table 4.5: Allowable Stress for Masonry.................. 71 Table 4.6: Allowable Stress for Concrete.................. 71

Table 4.7: Slenderness Ratio................. 73

Table 5.1: Gravity Load Calculations.................. 79 Table 5.2: Wind Loads for 10 Story Building................. 80 Table 5.3: Beams Schedule for A 10 Story Steel Moment Frame............... 82 Table 5.4: Columns Schedule for A 10 Story Steel Moment Frame............... 82 Table 5.5: Beams Schedule for A 10 Story Concrete Moment Frame................ 83 Table 5.6: Columns Schedule for A 10 Story Concrete Moment Frame................. 83 Table 5.7: Beams Schedule for A 10 Story Steel Braced Frame................. 84

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Table 5.8: Columns Schedule for A 10 Story Steel Braced Frame................... 84 Table 5.9: Braces Schedule for A 10 Story Steel Braced Frame................... 84 Table 5.10: Beams Schedule for A 10 Story Concrete Shear Wall................. 85 Table 5.11: Columns schedule for a 10 story concrete shear wall............... 85 Table 5.12: Labor and Material Cost for A 10 Story Steel Moment Frame................ 86 Table 5.13: Labor and Material Cost for A 10 Story Steel Braced Frame.................. 86 Table 5.14: Labor and Material Cost for A 10 Story Conc. Moment Frame............... 86 Table 5.15: Labor and Material Cost for A 10 story Concrete Shear Wall................. 86 Table 5.16: Wind Loads for 20 Story Building............... 87 Table 5.17: Beams Schedule for A 20 Story Steel Moment Frame................ 89 Table 5.18: Columns Schedule for A 20 Story Steel Moment Frame................. 89 Table 5.19: Beams Schedule for A 20 Story Concrete Moment Frame.................. 90 Table 5.20: Columns Schedule for A 20 Story Concrete Moment Frame............... 90 Table 5.21: Beams Schedule for A 20 Story Steel Braced Frame............... 91 Table 5.22: Columns Schedule for A 20 Story Steel Braced Frame............... 91 Table 5.23: Braces Schedule for A 20 Story Steel Braced Frame............... 91 Table 5.24: Beams Schedule for A 20 Story Concrete Shear Wall................. 92 Table 5.25: Beams Schedule for A 20 Story Concrete Shear Wall................. 92 Table 5.26: Labor and Material Cost for A 20 Story Steel Moment Frame................ 93 Table 5.27: Labor and Material Cost for A 20 Story Steel Braced Frame............... .. 93 Table 5.28: Labor and Material Cost for A 20 Story Conc. Moment frame............... 93 Table 5.29: Labor and Material Cost for A 20 Story Concrete Shear Wall................ 93 Table 5.30: Wind Loads for 30 Story Building............... 94

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Table 5.31: Beams Schedule for A 30 Story Steel Moment Frame................ 96 Table 5.32: Columns Schedule for A 30 Story Steel Moment Frame................. 96 Table 5.33: Beams Schedule for A 30 Story Concrete Moment Frame.................. 97 Table 5.34: Columns Schedule for A 30 Story Concrete Moment Frame............... 97 Table 5.35: Beams Schedule for A 30 Story Steel Braced Frame............... 98 Table 5.36: Columns Schedule for A 30 Story Steel Braced Frame............... 98 Table 5.37: Braces Schedule for A 30 Story Steel Braced Frame............... 98 Table 5.38: Beams Schedule for A 30 Story Concrete Shear Wall................. 99 Table 5.39: Beams Schedule for A 30 Story Concrete Shear Wall................. 99 Table 5.40: Labor and Material Cost for A 30 Story Steel Moment Frame................ 100 Table 5.41: Labor and Material Cost for A 30 Story Steel Braced Frame.................. 100 Table 5.42: Labor and Material Cost for A 30 Story Conc. Moment Frame............... 100 Table 5.43: Labor and Material Cost for A 30 Story Concrete Shear Wall................ 100 Table 5.44: Wind Loads for 40 Story Building............... 101 Table 5.45: Beams Schedule for A 40 Story Steel Moment Frame................. 103 Table 5.46: Columns Schedule for A 40 Story Steel Moment Frame................. 103 Table 5.47: Beams Schedule for A 40 Story Concrete Moment Frame.................. 104 Table 5.48: Columns Schedule for A 40 story Concrete Moment Frame............... 104 Table 5.49: Beams Schedule for A 40 Story Steel Braced Frame............... 105 Table 5.50: Braces Schedule for A 40 Story Steel Braced Frame............... 105 Table 5.51: Columns Schedule for A 40 Story Steel Braced Frame............... 106 Table 5.52: Beams Schedule for A 40 Story Concrete Shear Wall. 107 Table 5.53: Columns Schedule for A 40 Story Concrete Shear Wall.................. 107

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Table 5.54: Labor and Material Cost for A 40 Story Steel Moment Frame................ 108 Table 5.55: Labor and Material Cost for A 40 story Steel Braced Frame............... 108 Table 5.56: Labor and Material Cost for A 40 Story Conc. Moment Frame............... 108 Table 5.57: Labor and Material Cost for A 40 Story Concrete Shear Wall................ 108

Table 5.58: Total Cost Comparison for 10 Story Building.................. 109 Table 5.59: Total Cost Comparison for 20 Story Building.................. 109 Table 5.60: Total Cost Comparison for 30 Story Building.................. 109 Table 5.61: Total Cost Comparison for 40 Story Building.................. 109 Table 6.1: Lateral Drift Comparison for 10 Story Building.................. 111 Table 6.2: Lateral Drift Comparison for 20 Story Building.................. 114 Table 6.3: Lateral Drift Comparison for 30 Story Building.................. 117 Table 6.4: Lateral Drift Comparison for 40 Story Building.................. 120 Table A.1: One - Way Solid Slab Criteria................. 144 Table A.2: Two - Way Solid Slab Criteria................ 145 Table A.3: Two - Way Flat Slab Criteria............... 146 Table A.4: Two - Way Flat Plate Slab Criteria.................. 147 Table A.5: One - Way Joist Slab Criteria.................. 148 Table A.6: Two - Way Waffle Slab Criteria.................. 149 Table B.1: Moment Frame System Criteria............... 150 Table B.2: Diagonal Braced Frame System Criteria................. 151 Table B.3: Shear Wall System Criteria.................. 152 Table B.4: Shear Wall and Frame System Criteria................ 153 Table B.5: Tube System Criteria............... 154

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Table B.6: Framed Tube System Criteria.................. 155 Table B.7: Staggered Truss System Criteria.................. 156

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List of Figures

Figure 1.1: Structural Systems............... 3 Figure 1.2: Selection of Structural System Process............... 4 Figure 1.3: Kingdom Tower and Al Faisalih Tower in Riyadh................. 6 Figure 1.4: Hurricane and Buildings Collapse Causing by Hurricane................. 7 Figure 2.1: Prototype, Perspective, Plan, and Section............... 9 Figure 2.2: STAAD Pro2005 Logo. (STAAD Software).................. 10 Figure 2.3: Selection of Structural Systems and Materials Process............... 13 Figure 2.4: Lateral Drift Under Wind Load............... 14 Figure 3.1: Case Study Selection Process................ 18 Figure 3.2: Building Systems Integration................ 20 Figure 3.3: Span Ranges for Structure Elements.................. 22 Figure 3.4: Span Ranges for Structure Systems................ 23 Figure 3.5: Gravity Load Types................. 24 Figure 3.6: Seismic Waves................ 25 Figure 3.7: Richter Scale Method.................. 26 Figure 3.8: (a) Surface Waves (b) Body Waves................. 26 Figure 3.10: Structural Members Under Vertical and Lateral Loads.................. 29 Figure 3.11: Schematic Structures (a) Concrete Beam (b) I Steel Beam............... 31 Figure 3.12: Structure Systems vs. Height................ 35 Figure 3.13: Thermal Reservoir Comparisons............... 37 Figure 3.14: End Bearing Piles.................. 38

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Figure 3.15: Truss (a) vs. Vierendeel (b) Duct constraints................ 40 Figure 4.1: Wind flow Around a Tall building.................. 43 Figure 4.2: Relation of Wind Velocity to Pressure on a Stationary Object.................. 44 Figure 4.3: General Effects of Wind.................. 46 Figure 4.4: Wind Pressure on Building................ 47 Figure 4.5: Building (A), Wind force (Fx), Shear force per level (Vx) Overturn moment (Mx), Overturn visualized (B)............... 48 Figure 4.6: Wind Speed in Saudi Arabia........................................................................... 51 Figure 4.7: Wind Exposures; Inner City, Open area, & Near ocean................ 52 Figure 4.8: Leeward and Windward Pressure Distrubution.............................................. 53 Figure 4.9: Kz Graph............... 54 Figure 4.10: Drift in a Building Subjected to Lateral Wind Forces............... 56 Figure 4.11: Moment Frame Deformation Types.................. 60 Figure 4.12: Moment Frame (A) and Deformation Under Wind Load (B)............... 61 Figure 4.13: Braced Frame Deformation Types................ 63 Figure 4.14: Braced Frame (A), Predominantly Shear Deflection (B) , and Flexural Mode.................. 64 Figure 4.15: Functions of Shear Walls.................. 65 Figure 4.16: Shear Walls Types 1................. 66 Figure 4.17: Drift Configuration of Shear Wall-Frames Structure................ 67 Figure 4.18: Interaction Between Braced Frame and Moment Frame............... 68 Figure 4.19: Shear Walls Types................ 72 Figure 4.20: Slenderness Ratio.................. 73

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Figure 4.21: 20 Story Frame Configuration.................. 75 Figure 5.1: 10 Story (130 ft) Height Prototype Frame; Plan (a), Section (b), Wind and gravity load (c)................ 78 Figure 5.2: Structural Framing Plan With Loads Distribution on Beams for 10 Story Building................. 79 Figure 5.3: Combined Stresses of Beams for Steel Moment Frame for 10 Story Building.................. 81 Figure 5.4: Combined Stresses of Columns for Steel Moment Frame for 10 Story Building.................. 81 Figure 5.5: Combined Stresses of Beams and Columns for Concrete Moment Frame for 10 Story Building................ 81 Figure 5.6: Combined Stresses of Beams and Columns for Concrete Shear Walls for 10 Story Building.................. 81 Figure 5.7: Combined Stresses of Beams for Steel Braced Frame for 10 Story Building.................. 81 Figure 5.8: Combined Stresses of Columns for Steel Braced Frame for 10 Story Building.................. 81 Figure 5.9: Perspective of a 10 Story Steel Moment Frame.................. 82 Figure 5.10: Perspective of a 10 Story Concrete Moment Frame................ 83 Figure 5.11: Perspective of a 10 Story Steel Braced Frame................ 84 Figure 5.12: Perspective of a 10 Story Concrete Shear Wall.................. 85 Figure 5.13: 20 Story (260 ft) Height Prototype Frame; Section (a),Wind and gravity load (b).................87 Figure 5.14: Combined Stresses of Beams for Steel Moment Frame for 20 Story Building.................. 88 Figure 5.15: Combined Stresses of Columns for Steel Moment Frame for 20 Story Building.................. 88

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Figure 5.16: Combined Stresses of Beams and Columns for Concrete Moment Frame for 20 Story Building................ 88 Figure 5.17: Combined Stresses of Beams and Columns for Concrete Shear Walls for 20 Story Building..... 88 Figure 5.18: Combined Stresses of Beams for Steel Braced Frame for 20 Story Building...... 88 Figure 5.19: Combined Stresses of Columns for Steel Braced Frame for 20 Story Building.................. 88 Figure 5.20: Perspective of a 10 Story Steel Moment Frame.................. 89 Figure 5.21: Perspective of a 20 Story Concrete Moment Frame 90 Figure 5.22: Perspective of a 20 Story Steel Braced Frame 91 Figure 5.23: Perspective of a 20 Story Concrete Shear Wall.................. 92 Figure 5.24: 30 Story (390 ft) Height Prototype Frame; Section (a), Wind and Gravity Load (b). 94 Figure 5.25: Combined Stresses of Beams for Steel Moment Frame for 30 Story Building.................. 95 Figure 5.26: Combined Stresses of Columns for Steel Moment Frame for 30 Story Building.................. 95 Figure 5.27: Combined Stresses of Beams and Columns for Concrete Moment Frame for 30 Story Building 95 Figure 5.28: Combined Stresses of Beams and Columns for Concrete Shear Walls for 30 Story Building..... 95 Figure 5.29: Combined Stresses of Beams for Steel Braced Frame for 30 Story Building..... 95 Figure 5.30: Combined Stresses of Columns for Steel Braced Frame for 30 Story Building..... 95 Figure 5.31: Perspective of a 30 Story Steel Moment Frame..... 96 Figure 5.32: Perspective of a 30 Story Concrete Moment Frame... 97

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Figure 5.33: Perspective of a 30 Story Steel Braced Frame... 98 Figure 5.34: Perspective of a 30 Story Concrete Shear Wall...... 99 Figure 5.35: 40 Story (520 ft) Height Prototype Frame; Section (a), Wind and Gravity Load (b). 101 Figure 5.36: Combined Stresses of Beams for Steel Moment Frame for 40 Story Building.................. 102 Figure 5.37: Combined Stresses of Columns for Steel Moment Frame for 40 Story Building.. 102 Figure 5.38: Combined Stresses of Beams and Columns for Concrete Moment Frame for 40 Story Building 102 Figure 5.39: Combined Stresses of Beams and Columns for Concrete Shear Walls for 40 Story Building..... 102 Figure 5.40: Combined Stresses of Beams for Steel Braced Frame for 40 Story Building...... 102 Figure 5.41: Combined Stresses of Columns for Steel Braced Frame for 40 Story Building.................. 102 Figure 5.42: Perspective of a 40 Story Steel Moment Frame.................. 103 Figure 5.43: Perspective of a 40 Story Concrete Moment Frame 104 Figure 5.44: Perspective of a 40 Story Steel Braced Frame 105 Figure 5.45: Perspective of a 40 Story Concrete Shear Wall.................. 107

Figure 6.5: Lateral Drift in Inches for a 20 Story Building... 111 Figure 6.1: Lateral Drift in Inches for a 10 Story Building... 112 Figure 6.2: Lateral Drift of 10 Story Building Under Wind Pressure... 112 Figure 6.3: Lateral Drift Reduction as Percent of Allowable for 10 Story Building.. 113 Figure 6.4: Lateral Drift under Wind Pressure for 20 Story Building... 114

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Figure 6.7: Lateral Drift Reduction as Percent of Allowable for 20 Story Building.................. 115 Figure 6.8: Lateral Drift under Wind Pressure for 30 Story Building... 116 Figure 6.9: Lateral Drift in Inches for a 30 Story Building... 117 Figure 6.10: Lateral Drift Reduction as Percent of Allowable for 30 Story Building...... 118 Figure 6.11: Lateral Drift under Wind Pressure for 40 Story Building... 119 Figure 6.12: Lateral Drift in Inches for a 40 Story Building... 120 Figure 6.13: Lateral Drift Reduction as Percent of Allowable for 40 Story Building...... 121 Figure 6.14: Lateral Drift in Inches for Steel Moment Frame..... 122 Figure 6.15: Lateral Drift in Inches for Concrete Moment Frame...... 122 Figure 6.16: Lateral Drift in Inches for Concrete Shear Wall..... 123 Figure 6.17: Lateral Drift in Inches for Steel Braced Frame... 123 Figure 6.18: Cost Comparisons Per ft for 10 Story Building..... 124 Figure 6.19: Percentage of Cost Reductions for 10 Story Building.... 125 Figure 6.20: Total Cost of 10 Story Building...... 125 Figure 6.21: Cost Comparisons Per ft for 20 Story Building. 126 Figure 6.22: Percentage of Cost Reductions for 20 Story Building.... 127 Figure 6.23: Total Cost of 20 Story Building...... 127 Figure 6.24: Cost Comparisons Per ft for 30 Story Building. 128 Figure 6.25: Percentage of Cost Reductions for 30 Story Building129 Figure 6.26: Total Cost of 30 Story Building.................. 129 Figure 6.27: Cost Comparisons Per ft for 40 Story Building. 130

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Figure 6.28: Percentage of Cost Reductions for 40 Story Building 131 Figure 6.29: Total Cost of 40 Story Building.................. 131 Figure 6.30: Total Cost for Concrete Moment Frame. 132 Figure 6.31: Total Cost for Steel Moment Frame.... 133 Figure 6.32: Total Cost for Concrete Shear Wall 133 Figure 6.33: Total Cost for Steel Braced Frame.................. 134 Figure 6.34: Steel Weight for Steel Moment Frame 135 Figure 6.35: Steel Weight for Steel Braced Frame.. 135 Figure 6.36: Concrete Volume for Concrete Moment Frame.................. 136 Figure 6.37: Concrete Volume for Concrete Shear Wall. 136

Figure 7.1: Lateral Drift Comparisons for Different Structural Systems and Heights... 137 Figure 7.2: Total Cost Comparisons for Different Structural Systems and Heights... 139 Figure A.1: Perspective of One-Way Solid Slab 144 Figure A.2: Perspective of Two-Way Solid Slab... 145

Figure A.3: Perspective of Two-Way Flat Slab..... 146 Figure A.4: Perspective of Two-Way Flat Plate Slab.... 147 Figure A.5: Perspective of One-Way Joist Slab..... 148 Figure A.6: Perspective of Two-Way Waffle Slab..... 149 Figure B.1: Perspective of Moment Frame System.... 150 Figure B.2: Perspective of Diagonal Braced Frame System... 151 Figure B.3: Perspective of Shear Wall System... 152 Figure B.4: Perspective of Shear Wall and Frame System..... 153

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Figure B.5: Perspective of Tube System..... 154 Figure B.6: Perspective of Framed Tube System... 155 Figure B.7: Perspective of Staggered Truss System... 156

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Abstract

This thesis proposes procedures and guidelines for selection of optimum structural

systems and materials in two stages. Stage one is based on a list of criteria, including

architectural considerations. Stage two evaluates selected systems and materials for

optimum performance of criteria considered critical for a given project. A tall office

building in Dammam Saudi Arabia is used as case study to compare three structural

systems: moment frame, braced frame, and shear wall; as well as two materials: concrete

and steel. The case study considers four building heights: 10, 20, 30, and 40 stories. The

STAAD Pro 2005 software is used to analyze these systems according to allowable stress

requirements for an objective function to minimize drift, at minimal cost for wind speed

of 90 miles per hour. Shear wall is the optimum structural system and concrete the

optimum material to minimize lateral drift at minimum material and labor costs.

Keywords: lateral drift, wind load, IBC 03, allowable stress, STAAD Pro

1

Chapter 1 Introduction

1.1 Introduction This chapter introduces the objectives, scope of study and a brief introduction to

structural systems, selection of structural systems, and selection of criteria. In addition, it

includes an analysis of tall buildings in Saudi Arabia and wind load considerations.

1.2 Objective and Scope of Study The objective of this thesis is to develop a formal process and guidelines to select optimal

structural systems and material which minimize lateral drift in tall buildings in Saudi

Arabia in relation to cost.

The process involves three stages:

Stage 1: Pre-select systems based on a list of criteria

Stage 2: Select a case study system, considering moment frame, braced frame, shear wall

Stage 3: select material, considering steel or concrete

This process is conducted for tall buildings of various heights in Dammam, Saudi Arabia.

The STAAD software is used to analyze theses systems according to the allowable stress

requirements for an objective function to minimize drift, at minimum material and labor

costs for maximum wind speed of 90 miles / hour.

1.3 Selection Steps

1- Pre-select appropriate systems based on a list of criteria

2- Test structural systems (moment &braced frame, shear wall) under lateral load

3- Compare drift of each structural system and material to select the optimum one.

4- Reduce the basic labor and materials costs.

2

1.4 Structural Systems and Materials

A structural system is defined as the main part of the building which carries and transfers

the loads, both vertical and lateral, safely to the soil through the foundation. Structural

systems consist of many elements, including: floor slabs, decks, joists, beams, girders,

shear walls, columns, braces, and foundations. Structure systems involve horizontal and

vertical systems. Horizontal systems include bending resistant systems (beam systems,

Vierendeel, folded plate, cylindrical shell); axial resistant (truss, space truss, tree); form

resistant (arch, vault, dome, grid shell, HP shell, etc.); tensile resistant (suspended and

stayed systems, etc.). Vertical systems include: moment frame, braced frame, shear wall,

cantilever, framed tube, braced tube, bumbled tube, suspended high-rise, etc. (Fig. 1.1).

Each system has advantages as well as different purposes. For example, a moment frame

is recommended for use in office buildings in order to provide free flexible space for

rental purpose. Shear walls are good to use for hotels and apartments to provide lateral

force resistance as well as sound transmission isolation and unit separation. Furthermore,

each structural system has a different level of stiffness. For example, a moment frame is

more flexible than a braced frame system. In contrast, a shear wall system is more rigid

than a braced frame system. Shear walls and braced frames are better to resist wind load,

while ductile moment frames are better to resist seismic load.

3

(a) (b)

(c) (d)

Figure 1.1: Structural systems (a) Moment frame, (b) braced frame, (c) shear wall, (d) Cantilever. (Schierle, 2006, p 3-10)

There are also several alternative structural building materials: steel, concrete, masonry,

wood, aluminum, and fabric. Each material has different properties as well as different

purposes. For example, wood buildings are the most popular buildings in the United

States because they are light, minimize seismic load, as well as wood is readily available

and relatively cheap compared to concrete and steel . In contrast, concrete buildings are

the most popular buildings in Saudi Arabia because wood is not available and concrete is

good to resist wind load. Concrete is also cheaper than steel which is less available.

1.5 Selection of Structural Systems

The selection of structural system is sometimes based on personal experience or

perception without being evaluated as it should be to provide advantage for the project.

The conceptual selection process provides an orderly way to determine and review vital

criteria which leads to the selection of the optimum structural system (CRSI 1997 p2).

The structural system should be integrated and accommodated to other building systems,

like: architectural, mechanical, electrical, and building services.

However, the selection of the structural system is often passed through many processes,

as shown in figure 1.2. At the beginning of the process the criteria and requirements

should be determined. The second step is applying different structural systems to the

criteria and requirements. The third step is testing and evaluating the performance of each

structural system. The forth step is developing and modifying the tested system and

retesting as well as evaluating it again. The last step is selecting the optimum structural

system and material.

4

Figure 1.2: Selection of structural system process

5

1.6 Selection Criteria The selection process is very wide in scope and contains every aspect that could affect

the selection of structural system. Determining the required criteria depends on owner

needs, project constraints, and project requirements (CRSI 1997 p3). A smart or an

optimum structural system is that system which achieves most of the required criteria.

There are many critical criteria that affect the selection of structural systems and

materials, and this thesis proposes 40 of them like: gravity load, lateral load (wind and

seismic), climate conditions, labor and material costs, code requirements, building

location, building height limit, sustainability (durable and recyclable), strength, stiffness,

stability, and synergy. For example, building location is a significant criterion which

affects the selection of material. In Saudi Arabia, the most popular building material is

concrete; while wood is not available and steel is very expensive. The main investigated

criterion is minimizing the lateral drift in tall buildings in Saudi Arabia in order to

provide occupant comfort and protect them and the properties. The secondary criterion is

minimizing labor and material cost. Chapter three shows the list of selection criteria and a

brief description for each one.

1.7 Tall Buildings in Saudi Arabia

The Kingdom of Saudi Arabia is a rapidly developing modern country, containing a rich

variety of building structure systems and materials, such as concrete and steel. In order to

support building industrialization in Saudi Arabia, the government of Saudi Arabia hired

many famous architects and structural engineers, such as Norman Foster, to design some

vital buildings. In large cities of Saudi Arabia like Riyadh, Jeddah, and Dammam, the

population is rapidly increasing. This requires a rapid increase of building construction in

order to meet peoples needs. For example: in Riyadh, the capital of Saudi Arabia, the

population is approximately 4.3 million people, which requires a large land area. (The

purpose behind building high-rise buildings is because there is a shortage in land

availability so the land cost is very high. Most people cannot afford these land prices and

one solution is to build high-rise buildings). Figure 1.3 shows the most popular highrise

building in Riyadh. These buildings became marks land of Saudi Arabia and are listed

with the highest buildings in the world. These buildings have different occupancies, like

offices, hotels, shopping centers, and apartments in order to meet peoples needs. Hence,

because of the high demand to build more high-rise buildings in Saudi Arabia, this thesis

will investigate the structural performance of tall buildings in Saudi Arabia in order to

select the best structural systems and material which improve the performance of the

building to resist the lateral force like strong winds and earthquakes.

(a) (b)

Figure 1.3: (a) Kingdom tower, (b) Al Faisalih tower in Riyadh (http://www.moudir.com/vb/showthread.php?t=95655)

6

1.8 Wind Load Considerations

Wind load is a critical force that causes many disasters, as can be seen in Figure 1.4.

Because in Saudi Arabia wind load is more critical than seismic load, this thesis investigates

wind effect on tall buildings in Saudi Arabia. The peak wind speed in Dammam city is

about 90 mph (miles per hour). Wind load increases with height on tall buildings. Wind

causes lateral deflection (drift) on tall buildings and requires careful consideration to control

drift. To minimize lateral drift in tall buildings it is necessary to select the optimum

structural systems and materials which help to minimize drift. Controlling drift is vital to

provide occupant comfort and avoid motion sickness. Furthermore, large drift may endanger

life and incur loss of property or even cause building collapse.

(a) (b)

Figure 1.4: (a) Hurricane, (b) buildings collapse causing by hurricane

(http://www.fws.gov/home/hurricane/)

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8

Chapter 2 Research Methodology

2.1 Introductions This chapter describes the research methodology, such as data collection and analysis. In

addition, it shows the various tools which are used.

2.2 Data Collection Methods The thesis data is collected from different sources which are: reference books, published

papers, articles, interviews, lectures, previous MBS thesis, and some working drawings.

Since this thesis investigates tall buildings in Saudi Arabia, some data is collected from

consulting offices in Dammam, Saudi Arabia: for example, wind speed, code

requirements, and the methodology of design. The official building code used in Saudi

Arabia is the International Building Code IBC 03. Some information about material and

labor cost is collected through phone calls with AL Zamil steel factory as well as some

construction companies in Saudi Arabia. In addition, one of the vital methods of

collection data interviewed the thesis committee members: Prof. Schierle, Prof. Noble,

Mr. Vergun, Prof. Speigehalter, and Dr. ALSatari.

2.3 Thesis Tools and Testing Model 2.3.1 Testing Model: The thesis tested a large part of the building as prototype instead of testing the whole

building; however, the test is done for an office building because the function of the

building could be accommodated with many types of structural systems, including

moment frame, braced frame, and shear wall. The typical story height for office buildings

is about 13 feet. Width and length of the horizontal plan are determined by program

needs and the code requirements for expansion joints. The maximum distance for the

expansion joint should not exceed 30 m or (100 feet). The plan dimension of the tested

proptotype is 100 feet 100 feet. As shown in fig. 2.1 the plan consists of three equal

bays (33.3x33.3 ft). Furthermore, the first suggested height of the building is determined

by fire safety requirements in Saudi Arabia; the minimum considered height of a high rise

building is about 10 floors. The investigation is for 20, 30, and 40 stories.

(a) (b) (c)

Figure 2.1: Prototype: (a) perspective, (b) plan, (c) section

2.3.2 STAAD Pro 2005 Software

The Structural Analysis and Design program is the most popular structural software in

Saudi Arabia; it is used in most of the structural consulting offices and the universities of

Saudi Arabia. This program is used to analyze and design all types of structural system

and material. Therefore, this program is used as the main tool of this investigation.

9

Figure 2.2: STAAD Pro2005 logo. (STAAD Software)

2.4 Design Methods The allowable stress design method is used for schematic structural design and analysis

material strength: concrete 9.0 ksi, steel: 50 ksi. Structural members are designed to meet

the allowable stresses, using safety factors of 45% for concrete and 60% for steel (4 ksi

concrete, 30 ksi steel beam; 25 ksi steel columns due to buckling) In order to minimize

structural elements size, and to reduce the cost. For example, as shown in table 2.1, the

combined axial and bending stresses for concrete beams and columns meet the maximum

allowable stress 4000 psi (4 ksi).

Table 2.1: Combined axial and bending stresses for 20 story concrete moment frame

10

As can be seen in table 2.2 the combined axial and bending stresses for a 20 story steel

moment frame for 33.33 ft steel beams are 29,257 psi while the maximum allowable

stress is 30,000 psi (30 ksi). As for 13 ft steel columns as shown in table 2.2, the

combined stresses 24,415 psi while the maximum allowable stress is 25,000 psi (25 ksi)

for buckling.

Table 2.2: Combined axial and bending stresses for 20-story Steel Moment frame

Member sizes are based on combined wind and gravity loads. Beam and column sizes

vary every two floors as shown in the tables. Wide flange steel columns and beams are

used for steel buildings in this test (W14 for columns and W18 for beams) because they

are common in Saudi Arabia and United States. As shown in table 2.3 the allowable axial

loads in kips for wide flange columns (w14) for different yield strength as well as

different weight. However, to check the efficiency of strength for selected section, the

allowable axial loads should be checked per inch. For example, the allowable axial loads

11

Selected section (50 ksi), kL = 13:

W14x176, A=51.8 in, Pallowable = 1347 kips (Use W14x176 )

Allowable stress = 1347 / 51.8 = 26 ksi > 25 ksi, O.K

12

Table 2.3: Allowable axial loads in kips for wide flange (W14)

(AISC, 1991, p3-22) 2.5 Data Analysis Method 2.5.1 Selection of Structural System Method Selection of structural system is done through many processes, as shown in figure 2.4.

For example, considering two materials (steel and concrete), three structural systems

(moment frame, braced frame, and shear wall); this process implies four combinations of

structural systems and materials for each building height. Each material and system

combination is passed through a criteria process to minimize lateral drift (main criteria)

as well as minimizing labor and material costs (secondary criteria). All material and

structural system combinations are entered to the design evaluation of STAAD Pro 2005.

Comparing all result leads to the selection of the optimum structural system and material.

Figure 2.3: Selection of structural systems and materials process

2.5.2 Drift Measuring Method

The lateral drift is measured at each level after defining member size for strength to

assure the actual lateral drift is less than the maximum allowable drift (h/200). As can be

seen in fig. 2.4 which shows lateral drift under wind load, the measurement is taken at

each floor as well as comparing the actual lateral drift with the maximum allowable drift.

Table 2.4 shows the measurement of the maximum actual lateral drift (deflection) in

STAAD pro software.

13

14

Figure 2.4: Lateral drift under wind load

Table 2.4: Measuring the maximum actual lateral drift (deflection)

15

Chapter3 Selection Criteria

3.1. Introduction The structural system is considered as the most vital system in the building for many

reasons. First, it usually has the highest cost compared to other building systems cost.

Second, the structural system is required for a building to stand up. The other building

systems should be accommodated and adapted to it, for example, the mechanical

equipment, air conditioning ducts and other services must be integrated with the

structural system and elements. Finally, the structural system should save occupants and

properties from natural forces, such as gravity, wind and seismic loads.

The selection criteria method is very wide in scope and includes not only structural

aspects but also architectural considerations. Determining the required criteria depend

on owner needs, project constraints, and project requirements (CRSI 1997, p3).

Architects and engineers should select the structural system according to criteria defined

jointly by building owners, architects and structural engineers following are 42 criteria

proposed to select structural systems and materials.

16

3.2. Proposed General Criteria List 1- Material cost

2- Labor cost

3- Integration and synergy

4- Ease of construction

5- Span limits

6- Gravity load

7- Lateral load (wind and seismic)

8- Noise and vibration control

9- Fire safety and protection

10- Sustainability (durability and recyclable)

11- Strength, Stiffness, Stability, and Synergy

12- Corrosion and moisture resistance

13- Maintenance cost (life cycle cost)

14- Material transportation

15- Material availability (resources)

16- Design possibilities (structural freedom)

17- Environmental Impact and energy consumption of production

18- Building type (function of building)

19- Building location

20- Building height limit

21- Code requirements

22- Site conditions (access, storages)

17

23-Technology availability

24- Energy efficiency & thermal mass

25- Soil class and topography (flat or sloping)

26- Planning policy and constrains

27- Morphology

28- Weather condition

29- Security

30- Quality control

31- Exterior cladding system

32- Story height

33- Future modification like opening

34- Speed of construction

35- Resale and payback

36- Leverage cash flow

37- Managing change

38- Healthy living & indoor air quality

39- Appearance

40- Building volume

41- Reduced Insurance Premiums

42- Building configuration

3.3. Case Study Selection Process

Figure 3.1: Case study selection process

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19

3.4. Structural Criteria 3.4.1. Material Cost

Material cost affects the selection of structure system. Material cost depends on many

factors like availability, energy consumption for production, abundance or shortage and

economic condition of the country. Obviously, local material cost will be much cheaper

than imported material. For example, in Saudi Arabia, the Hadeed Company which is

considered the biggest provider of steel in the Middle East imports steel from Mexico

and Brazil; which causes steel costs in Saudi Arabia to be more expensive than steel

prices in the United States (Mohammed, 2006). On the other hand, concrete cost in

Saudi Arabia is much cheaper than concrete cost in the United States because of the

resources and the production abundance as well as the labor cost, notably for formwork.

3.4.2. Labor Cost

Labor cost depends on many factors, like location, the skill of labor, complexity of the

work, as well as the economical situation of the country. However, the labor cost also is

influenced by the same factors that affect the material cost. For example, in poor

countries the labor cost is less than the labor cost in rich countries. In addition, the

skilled labor cost is much higher than unskilled labor cost. For instance, the Saad

Company, a construction company in Saudi Arabia, pays about $500 per month for a

skilled mason while they pay about half as much for unskilled masons, i. e. $250 per

month (Eng. Mustafa 2006). Furthermore, the hourly labor rates differ from country to

country. For example, the hourly rate for skilled mason in Saudi Arabia is $5 while the

rate for a skilled bricklayer in the United States is $36.81 (ICEC 20 January 2006).

3.4.3. Integration and Synergy

A structural system should be accommodated and integrated with other building systems.

For example, as shown in figure 3.2, a structural floor slab, designed as one-way joist rib-

slab, the gaps between the joists are used to pass the services, like air conditioning ducts,

lighting, electric wires and water pipes. Furthermore, to avoid the obstacles of the main

girder, all girders are designed to be inverted and hidden beam in order to ease the

services passage under the beam. In addition, the structural module is designed in

correlation with the architectural module, which provided the interior partition walls

exactly over the slab joist in order to avoid slab shear over-stress.

Figure 3.2: Building systems integration.

3.4.4. Ease of Construction

Time means cost in construction. Therefore, engineers should select the fastest and

easiest construction system to save the time and cost but provide quality control. The ease

of construction depends on many factors like labor skills, design form and the type of

20

21

materials. For example, the labor skills can control the time and quality of the work.

Skilled labor can accomplish higher quality than unskilled labor. Also skilled labors need

less time than unskilled which will reduce the project cost. In addition, the design form or

shape will affect the ease of construction as well. For example, formwork for round

columns costs less than square columns in the US.

Also, the type of material affects the ease of construction. For example, in the United

States, steel usually costs less than concrete because it is prefabricated while concrete

requires formworks and much time.

3.4.5. Span Limits

The span limit affects the stiffness of a system. For example, short spans are stiffer than

long spans. In addition, different materials have different span limits as shown in figures

3.3, 3.4. For example, steel frames have longer span capacity than concrete frames.

Hence, the span selection is affected by many factors like materials type, structural

systems type, building type. There is a strong relationship between the span and the

thickness of members. For instance, when the span increases the thickness will increase

as well. Furthermore, increasing the span will increase the cost. On the other hand,

minimizing the span much than the normal will increase the material quantity as well as

the cost (Othman, 2002). Hence, the selection of span should moderate the balance of

the long or short span. Figure 3.3 shows span limits and span/depth ratios for structure

elements and materials. Figure 3.4 shows span limits and span/depth ratios for structure

systems and material.

Figure 3.3: Span ranges for structure elements. (G G Schierle, 2006, p E-2)

22

Figure 3.4: Span ranges for structure systems. (G G Schierle, 2006, p E-3)

23

3.4.6. Gravity load

Structural systems should be able to carry and resist vertical gravity load. There are

many types of gravity load like dead load, and live load which includes snow load.

Gravity load depends on many factors like building location, building occupancy,

structural material and structural system. For example, in regions without snow load,

like Saudi Arabia, the building structure should be designed for dead and nominal live

load. In contrast, in mountain areas like Switzerland the building should be designed to

resist actual snow load. Mountain snow load may be about 20 times greater than the

nominal load in an area without snow load (Schierle, 2006). Figure 3.5 shows various

types of gravity loads, like: Dead load (1), Live load (2), Distributed load (3), Uniform

distributed load (4), and Concentrated load (5).

Figure 3.5: Gravity load types (Schierle, 2006, p 2-2)

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3.4.7. Seismic Load

Earthquakes cause waves that transfer through underground layers until they reach to the

ground surface. These waves affect building structures by shaking building foundations.

Consequently, the building will respond to this motion. Seismic waves are defined by two

terms as can be seen in figure 3.6. The first term is the period which is shown as

horizontal line and defined as the time of one wave cycle and considered the most critical

issue. For example, a building with a period that is resonant with the ground period could

even collapse. The second term is the amplitude shown as vertical ordinate, defined as

the displacement of a wave perpendicular to the direction it moves (Schierle, 2006, p 9-

12).

Figure 3.6: Seismic waves (Schierle, 2006, p.9-12)

The earthquakes affect depends on many factors. For instance: the earthquakes

magnitude which are measured by the Richter scale. The Richter scale created by Charles

Richter in 1935 at the California Institute of Technology observes and measures the

earthquake magnitude (Schierle, 2006, p. 9-12). Figure 3.7 defines the Richter

magnitude as follows: Left line plots earthquake distance, right line plots amplitude

recorded on a seismograph; center line plots Richter Magnitude; defined by a line

connecting distance to the amplitude. For example, magnitude 4.5 is minor earthquake,

while 7.0 is a violent one. 25

Figure 3.7: Richter scale method (Schierle, 2006, p. 9-12)

There are several types of seismic waves (Fig. 3.8). For example, body waves consist of

P waves (Primary waves) that travel at high speed of 42,000 km/h), and S waves

(Secondary waves) that vibrate normal to the wave direction and affect the building by

dancing action. In addition, there are surface waves: Love waves and Raleigh waves.

Figure 3.8: (a) Surface waves (b) Body waves (Schierle, 2005, p6)

http://www.usc.edu/dept/architecture/mbs/struct/seismic/files/eq-ibc.pdf

26

27

Seismic force affects the building as base shear, which basically follows Newtons law:

F= m a (force = mass x acceleration) (Schierle, 2006, p. 9-12).

Due to this equation, structural engineers tend to minimize building mass and maximize

ductility (Schierle, 2006, p. 9-12). Therefore, to minimize building weight, requires

selecting lightweight materials and minimize structural members. Building design should

resist seismic forces to protect the building, people and property. Most people think that

rigid and strong buildings are best to resist seismic load. However, they are absolutely

wrong: rigid buildings are subject to greater seismic forces than ductile ones.

3.4.8. Noise Control

The selected structural material should be able to isolate the noise in buildings. For

example, in courthouses, hospitals, apartments and office buildings the selected material

should prevent or reduce sound transmission in order to provide privacy. Concrete

buildings have good sound rating according to standardized test (PCA & CRSI, p7).

Because concrete has high mass and density, it has excellent sound isolation, sound

absorption, and sound transmission reduction (PCA & CRSI, p7). For example, in

apartment buildings, the apartments should be separated by party walls to reduce sound

transmission. The party walls can also be shear walls and provide fire proofing. In

addition, concrete structures can resist vibration and electrical interference especially the

high-density (PCA & CRSI, p7).

28

3.4.9. Fire Safety

Fire safety is a critical issue to select the structure material. For example, concrete is

considered the best material to resist fire, compared to steel which requires fire proofing

to resist fire.

Steel starts to lose its strength at any temperature more than 300C and begins to

decrease strength at stable rate at about 800C. The melting temperature of steel is about

1500C (Colin Bailey). Hence, steel requires fire proofing (spray-on or other fire

proofing).

Concrete has low thermal conductivity, 50 times lower than steel. In addition, it heats so

slowly because of the density of aggregate and cement. Therefore concrete is ranked the

best fire resistant material (Colin Bailey). Hence, concrete does not require fire

protection like steel.

3.4.10. Sustainability (Durable and Recyclable)

Structural systems and materials should provide durability and sustainability to protect the

environment. Concrete is considered a natural material and widely available. For

example, the limestone, sand and clay, the main source of Portland cement production,

are almost without limit. In addition, fly ash from coal burning, gravel, sand, and crushed

stone are the main source of aggregate. Furthermore, the cement manufacturing process

uses combustible waste and tires as a fuel source (Publication & Communication LP

2006). Recycling of steel in the United States every year is more than recycling of

aluminum, plastic and glass combined with the industry's overall. The recycling of steel

rate is 64 %.( America Global Foundation 1996-2004). Each year, steel recycling saves

energy equivalent to powering about one-fifth of the households in the United States

(about 10 Million homes) for one year (America Global Foundation 1996-2004). Each

ton of recycled steel saves about 1.400 pounds of coal, 2,500 pounds of iron, and 120

pounds of limestone (America Global Foundation 1996-2004).

3.4.11. Strength, Stiffness, Stability, and Synergy

This criterion is considered a most significant issue to select the structure system and it

depends on many factors like types of loads, height of building, span limit and material

specification. As can be seen in the figure 3.9, the structure system should satisfy:

1- Strength to avoid and resist breaking.

2- Stiffness to avoid extreme deformation.

3- Stability to resist and avoid structural collapse.

4- Synergy to support and integrate the architectural design.

Figure 3.10: Structural members under vertical and lateral loads (Schierle, 2006, p.3-2)

29

30

3.4.12. Corrosion and Moisture Resistance

Corrosion resistance greatly depends on the type of material. Carbon dioxide in the air is

the main reason for corrosion, and corrosion is causing reduction of the lifespan of

structures. However, concrete ranks as the best material to resist corrosion and moisture

compared to other materials because of its density and mass. For example, concrete

protects steel bars from corrosion. Structural concrete members should be designed to

meet the code requirements to provide corrosion protection for steel bars. Exposed steel

may be protected by galvanizing, painting, or epoxy.

3.4.13. Material Transportation

Material should be selected locally in order to reduce transportation cost and to ensure

getting it on time. Cast in place concrete requires less transportation than steel, which

requires prefabrication in a shop while concrete is cast and mixed on site which requires

only ready-mix transportation. Transportation costs depend on the distance between the

project and factory. For instance, imported material will increase shipping costs and may

causing delay in construction schedule which will affect the cost of project. In contrast, if

the project is closed to the factory will be more economical and sustainable.

Transportation will also control and limit element size. Hence, transportation affects the

selection of structural materials.

3.4.14. Environmental Impact and Energy Consumption

Reduction of environmental pollution or impact is a new policy required, for a green

building and healthy environment. Before selection of structural material one should have

enough knowledge about the different materials and their environmental impacts. For

example, one study investigated two different types of structural beam. One of them is

reinforced concrete beam and the other is I- steel beam as shown in figure 3.11.

Figure 3.11: Schematic structures (a) concrete beam (b) I steel beam. (Leslie and Jonathan p209)

This study was done using the ATHENA database and computer program to study: Water

pollution, air pollution, solid waste, energy consumption, resource use, and global warming

potential. The investigation was done in Canada, which has the same cost and material

availability as the United States (Leslie and Jonathan p207). The test results show in table

3.1 resource use of about 48.85 kg reinforcement concrete and about 18.69 kg of steel. Table

3.1 also shows concrete and steel produced the same high mount of carbon dioxide, and

produced the same amount of solid waste as well. Steel produced 3 times more water

pollution than concrete. Steel also produced more air pollution than concrete. Finally, the

energy consumption for steel is much higher than the energy consumption of concrete.

31

Hence, the production of concrete is better than steel because it is consuming less energy

and less environmental impact (Leslie and Jonathan p 209).

Table 3.1: Environmental Impact of reinforced concrete and steel beams

(Leslie and Jonathan p210) 3.4.15. Low Maintenance Cost

The initial cost is very important to select structural material but the running cost, or

maintenance cost is also important. To estimate initial cost is relatively easy but to predict

running cost is more difficult. Even though, the life span of concrete buildings is expected

to be longer than that of steel buildings, whether steel and concrete are required periodic

maintenance and inspection (Tim Lease, P.E. 2003). For example, concrete should be

isolated from water to prevent water penetration to reach the steel bars that causes corrosion.

On the other hand, steel needs also painting, and maintaining the fireproofing and corrosion

resistance, which causes steel failure. (Tim Lease, 2003).

3.4.16. Design Possibility

The shape and size of buildings and structural elements is one of the most vital issues to

determine the type of structural material. Concrete can have any form since concrete seeks

the form (Madsen 2005). In addition, concrete allows adding an extra floor or any

horizontal extension as well. Furthermore, concrete could be switched from another type of 32

33

material like steel. For example, the New York City developer built Hotel & Tower at the

former Chicago Sun-Times site. This building switched from structural steel to concrete so

that two additional stories could be added to the 1,125-foot building. Also, the concrete slab

could be a flat slab which does not require beam space and thus will provide extra clear

height for each floor (Madsen, 2005). On the other hand, steel could be used for large span

projects while concrete is recommended for short spans. Steel can provide extra clear height

because the element size is much less than concrete (Madsen, 2005).

3.4.17. Material Availability

Selection of a local structural material is an axiomatic issue because imported material will

increase the cost because of shipping costs and limitation of transportation. However, the

material availability differs from country to country. For example, in Saudi Arabia concrete

is the most available material because the source of cement, aggregate, and sand are

provided while steel considered as imported material from Mexico and Brazil. In contrast,

the United States considered as one of the main producer of steel in the world. Even

thought, steel cost has increased in the last two years America is still able to produce about 6

million tons per year (Madsen, 2005). The total usage per year in the United States is about

4 million tons in the field of construction. Therefore, 2 million tons per year is considered

as redundant. On the other hand, most of states had shortage of cement in 2004 because of

event like the Florida hurricanes. Some of the United States have many companies who

produce cement, and thus build most of building of concrete. Cement companies will

increase by 2008 in these regions (Madsen, 2005).

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3.4.18. Building Type

Selection of structural system and material depends greatly on the building function. For

example, for factories or large stores the best system is a long span steel frame, while short

spans are good for housing and hospital buildings. Office buildings are better with moment

frame or braced frame in order to provide flexibility for partitions. By contrast, apartment

buildings require party walls to provide privacy, sound insulation, and fire resistance.

Courthouses and hospitals require the best material for noise isolation.

3.4.19. Building Location

Building location also affects selection of structural system and material. For example, if the

building is located in seismic zone, the building should be of lightweight material in order to

minimizing building mass. In contrast, heavyweight material is bets in hurricane zones in

order to maximize building mass to resist the wind load. Location by country will also affect

the selection of materials. For example, in Saudi Arabia it is better to use concrete in order

to resist the wind load and reduce cost while wood or steel are better in the United States

because these resources are abundant. Furthermore, each country has its own building code,

constrains, and policies which are different in each country.

3.4.20. Building Height Limit

This criterion is also a significant criteria to select structural systems and materials. Fazlur

Khan (Fig. 3.12) defined optimal structure system for various building heights, defined by

number of floors. Hence, building height depends on factors like structural system,

structural material, and drift control.

Figure 3.12: Structure Systems vs. Height (Schierle, 2006, p. 9-15)

3.4.21. Code Requirements

Structural design must follow building codes used in the country. Structural materials must

have the specification required by code. Building codes are different from country to

country. There are many building codes, such as: International building code (IBC),

uniform building code (UBC), Indian code, and Egyptian code, for example. In addition,

some country has several codes. For instance, the United States used to have several codes:

UBC in the west, BOCA on the east coast, and Southern Building Code in southern states.

Furthermore, some countries are using the others code; like in Saudi Arabia the current 35

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official used code is the International Building Code IBC 03. Building codes may be

adapted with variations depending on weather condition, land topography, and other special

conditions in seismic and hurricane zones. Building codes are updated about every three

years, based on new research and conditions.

3.4.22. Site Condition (Access and Storage)

One constraint to select structural system and material is the site condition. The site

conditions include the access to the site, storages area, site location, and the site topography.

For example, if the site access is small or limited, that will limit the type of equipment and

trucks that can reach the site. A site with large storage area could use cast in place concrete,

while prefab systems are better for tight sites. Also, site location is important to minimize

transportation distance and costs. For instance, for a project in Los Angeles downtown with

traffic jams, the contractor should get authorization to determine a convenient time for

material delivery.

3.4.23. Technology Availability

More and more, the field of architecture and structure has new developments and

technologies. Further, technology of structural systems and material may be available in one

country but not in other one. Hence, the selected system and material should be available

locally. For example, some countries have no steel production but produce concrete for

export In this case; use of the local material will minimize cost and avoid transportation

costs. Technology includes equipment and tools. For instance, crane height available may

control the maximum height of a building.

3.4.24. Energy Efficiency and Thermal Mass

The performance of structural material can be determined and measured by the energy

efficiency of the selected material. Each material has its own heat properties, like heat

absorption, transmission, and reflection. For example, concrete reduces temperature changes

in summer and winter season as well as adobe and stone structures do (PCA & CRSI p11).

In addition, concrete releasing and absorbing heat causes reduction of energy consumption

three ways:

First, concrete requires less energy to maintain constant interior temperature which saves the

monthly bill. Second, concrete has greater time lag between cooling load and peak heating

which delays heat transmission, consequently will reduce the monthly bill (PCA & CRSI

p11). Finally, concrete reduces initial building cost by using small cooling and heating

equipment because the concrete thermal mass lowers the cooling and heating loads as can be

seen in figure 3.13 the difference of heat gain between the concrete slab and steel metal deck

through 24 hours (PCA & CRSI p11).

Figure 3.13: Thermal reservoir comparisons (PCA & CRSI p11)

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3.4.25. Soil Class

There is a strong correlation between soil and building foundation Selection and design of

building foundation should be done after analyzing and examining the soil. There are six

types of soil in table 3.2: soft clay, stiff clay, sand compacted, gravel, sedimentary rock, and

hard rock (granite). Each type has a different capacity as shown in the table, ranging from 2

ksf (100 kPa) for soft clay to 200 ksf (9600 kPa) for the hard rock soil.

Table 3.2: Soil types and capacity (IBC table 1615.1.1, excerpts)

For example, if the soil is poor, it should be replaced with other type of soil or should be

excavated to a strong layer of soil. However, rock type soil can be build on and need no

excavation. On the other hand, some soft soils may require piles extending to stiffer layers

as shown in figure 3.13.

Figure 3.14: End bearing piles (Schierle, foundation lecture, 2006)

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3.4.26. Healthy Living & Indoor Air Quality

Indoor air quality affects healthy life, and requires appropriate specifications of material.

Sick buildings are building with materials which produce gases or other organic material

(PCA & CRSI p9). Each material has its own percentage of pollution, but concrete has the

lowest interior environment impact compared to other finish materials. Furthermore,

concrete does not require fire proofing or other coating material which causes indoor air

pollution (PCA & CRSI p9).

3.4.27. Morphology

Correlation and integration of structure system with the building function should be a major

objective. Each type of building has compatible structure systems and may not be

compatible with others. For example, for office buildings, moment frame or braced frame

systems provide flexible space for rental purpose; while apartments and hotels require party

walls for sound insulation and privacy that can also be used as shear walls and for fire

insulation. For exhibit halls and showrooms it is best to use large span structures to provide

flexible space with few columns to avoid blocking of views. By contrast, apartments and

hotels need no long span and may have short span to minimize structure depth and cost and

provide better stiffness. Structures should also correlate with the architectural morphology.

For example, trusses limit the size of ducts to pass through them while Vierendeel girders

allow larger ducts (Fig. 3.14).

Figure 3.15: Truss (a) vs. Vierendeel (b) duct constraints

3.4.28. Weather & Climate Conditions

Weather conditions obviously will affect the selection of structural material. For example, in

hot weather area like Saudi Arabia using of wood would not be recommended as much as

using of concrete or steel , since wood is not available. In addition, the weather conditions

include strong winds and snow. For instance, in high wind speed areas it is better to use

heavyweight material or braced frame system or shear walls in order to prevent uplift and

minimize the lateral drift caused by wind force. Hence, climate will affect the selection of

structural system and material as well. In snow area it is better to use the sloped roofs to

minimize snow load. To design for snow load will be necessary in order to prevent roof

collapse.

3.4.29. Security

According to current world events most buildings are designed to protect occupants from

external dangers. There are several methods to provide security for buildings. One of them is

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to select the safest structural material. Concrete is highly recommended in a valuable

building that requires a high level of security like data processing centers, hospitals, military

constructions, and nuclear facilities (CRSI p17 1997).

3.4.30. Exterior Cladding

Structural systems and materials should also be integrated with the exterior cladding.

Several types of exterior cladding are available: precast concrete, cast in place concrete,

masonry, glass, metal, stone, aluminum sheets, and marble. Cast in place concrete is one of

the best but most costly systems because it can act as exterior cladding and structural frame

as well. Furthermore, no need for connection between the structural element and the

architectural concrete walls. The exterior cladding system should be known in the first

structural stages in order to calculate their loads (CRSI, 1997, p. 17).

3.4.31. Minimal Story Height

Structural systems and materials should reduce story height as much as possible in order to

reduce the total cost as well. However, high stories are preferred for luxury housing.

Concrete structures require less story height than the other systems because flat plate floor

slab does not require a structural beam at all which helps to pass the service lines under the

slab. Reducing the exterior cladding height will minimize cost. In addition, reducing height

will reduce costs for plumbing, electrical, and HAVC. Furthermore, decreasing floor height

obviously will reduces building volume and then reduce HAVC consumption (CRSI p22

1997).

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3.4.32. Cash Flow and Financing Costs

Structural systems and materials should be adapted to the owner demands and his ability to

pay. For example, cost is different for cast in place and precast concrete. Steel fabrication

requires pre-financing and long time of order, while concrete requires less time and less

costs. Hence, concrete can save owner money, keeping money in the bank until the material

is ready. In addition, concrete can be provided in shorter time which will help to finish the

construction on time in comparison to steel which requires pre-order (CRSI p37 1997). For

example, the Wall Street journal project costs $175 million for construction and the delay to

finish this project cost $9 million per month ($3 million in interest and $6 million in lost

rent) for about $300,000 a day (CRSI, 1997, p37).

3.4.33. Building Configuration

Since the structure system is defined by the form of the building, there is a strong correlation

between structure system and building shape. The shape of building could be the shape of

plan or elevation. A complex shape will cost more than a simple shape, and may require a

specific material, labor skills, and technology.

3.4.34. Future Modification

Structural system should provide flexibility to allow future changes. Windows, doors, plan

layout, etc. may change in the future and require the structure to allow such changes.

Concrete floor slab like flat slab as well as flat plate slab are adoptive to this requirements

(CRSI, 1997, p25).

Chapter 4 Background

4.1. Introduction

This chapter describes the wind force effects on buildings and lateral force resisting systems.

In addition, it includes information about lateral drift in tall buildings as well as a previous

study about lateral drift.

4.2. Wind Force

Wind consists of blowing air as shown in figure 4.1. Air has mass and density that has

specific speed and blowing in specific direction. The energy of wind can be calculated

according to the following equation: E = 0.5mv (Ambrose & Vergun, 1995, p7).

Figure 4.1: Wind flow around a tall building (J. Holmes wind, 2001, p186)

4.2.1. Wind Situations

The initial stage of building design should take in account wind speed, based on ground

level wind. The wind situation according to figure 4.2 is considered: mild breeze 10 mph,

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stiff breeze 30 mph, windstorm periphery 50 mph, hurricanes 90 mph, violent hurricane 150

mph, and tornado up to 250 mph. (Ambrose & Vergun, 1987, p36).

4.2.2. Correlation of Wind Speed and Pressure

Wind forces affect the building through the air pressure that causes shear force on the

opposite direction. There is a strong correlation between wind speed, air pressure and shear

force. When wind speed increased the pressure on the vertical surfaces will increase as well

as the shear force. Figure 4.2 shows the relationship between wind speeds at left which

ranges from (0 to 250 mph) and at right wind conditions which vary from mild breeze to

tornado. The curved line visualizes the equation to calculate the equivalent static pressure on

buildings in relation to wind speed. (Ambrose & Vergun, 1995, p8)

Figure 4.2: Relation of wind velocity to pressure on a stationary Object (Ambrose & Vergun, 1987, p37)

4.2.3. General Wind Effects

Wind has strong effects on buildings. Wind causes shear force, lateral drift, and other

effects, as shown in figure 4.3.

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4.2.3.1. Direct Positive Pressure

Horizontal wind on a vertical building causes a force on the surface which faces the wind

direction (Ambrose & Vergun, 1995, p9).

4.2.3.2. Aerodynamic Drag

Wind affects building surfaces parallel to wind direction as well, as can be seen in figure

4.3. The wind affects the roof of the building in horizontal action which generates force on

the building forward wind direction path (Ambrose & Vergun, 1987, p38).

4.2.3.3. Negative Pressure (Suction)

On the building side opposite to the air path (leeward side), wind causes negative pressure

which is called suction. The suction acts outward on the surface of the building (Ambrose