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  1. 1. Wind Drift Design of Steel Framed Buildings: An Analytical Study and a Survey of the Practice Daniel Christopher Berding Thesis submitted to the faculty of the Virginia Polytechnic Institute and State University in partial fulfillment of the requirements for the degree of Master of Science in Civil Engineering Finley A. Charney W. Samuel Easterling ____________________ ____________________ Thomas M. Murray ____________________ June 29, 2006 Blacksburg, Virginia Keywords: structural steel, structural analysis, serviceability, wind, drift Copyright 2006, Daniel Christopher Berding
  2. 2. Wind Drift Design of Steel Framed Buildings: An Analytical Study and a Survey of the Practice Daniel Christopher Berding Abstract The design of steel framed buildings must take into consideration the lateral drift of the structure due to wind loading and any serviceability issues that may arise from this lateral movement. This thesis focuses on one of these issues, damage to nonstructural components. Although there are no specific requirements in the United States governing the effects of wind drift, it is an important issue which may significantly impact the buildings structural performance and economy. Furthermore, because these serviceability issues are not codified, there is a wide variation among design firms in how they are dealt with, leading to a greater economic disparity. This thesis begins with a comprehensive review of the literature that covers all pertinent aspects of wind drift in steel framed buildings. Next an analytical study of the variations in modeling parameters is performed to demonstrate how simple assumptions can affect the overall buildings stiffness and lateral displacements. A study is then carried out to illustrate the different sources of elastic deformation in a variety of laterally loaded steel frames. The different modeling variables demonstrate how deformation sources vary with bay width, the number of bays and the number of stories, providing a useful set of comparisons. To ascertain how serviceability issues are dealt with from firm to firm, a survey of the practice is developed to update the one conducted in 1988 (ASCE). In effect, the thesis is presented with the intention of suggesting and establishing a comprehensive, performance based approach to the wind drift design of steel framed buildings.
  3. 3. iii Acknowledgements The completion of this thesis and the attainment of my Masters Degree would not have been possible without the support and guidance from family, friends and the faculty of Virginia Tech. I would like to thank my Committee Chairman Dr. Finley A. Charney for providing assistance and guidance throughout my studies. The work I have done is largely a result of his previous and ongoing research. For the knowledge and insight that I have gained from working with him I am grateful. I would also like to thank Dr. Samuel Easterling and Dr. Thomas Murray for serving on my committee and enhancing my overall educational experience at Virginia Tech. "I get by with a little help from my friends." - John Lennon Without the support of family and friends none of this would have been achievable. I thank everyone who has been with me through this journey: my parents, siblings, my close friends. Special thanks goes out to Laurie Mazursky with whom I have shared countless hours throughout our undergraduate studies together at Vanderbilt University and graduate studies at Virginia Tech. Don't let schooling interfere with your education. - Mark Twain
  4. 4. iv Table of Contents Abstract............................................................................................................................... ii Acknowledgements............................................................................................................iii Table of Contents............................................................................................................... iv List of Figures................................................................................................................... vii List of Tables ..................................................................................................................... ix Chapter 1: Introduction ................................................................................................... 1 1.1 Philosophy of Design for Drift ........................................................................... 1 1.2 A Brief History of Wind and Structures ............................................................. 2 1.3 Project Scope ...................................................................................................... 5 REFERENCES ............................................................................................................... 8 Chapter 2: Literature Review.......................................................................................... 9 2.1 Introduction......................................................................................................... 9 2.2 Drift Limits and Damageability.......................................................................... 9 2.2.1 Definition of Damageability ....................................................................... 9 2.2.2 Drift and Damage Limits .......................................................................... 15 2.2.3 Codification of Serviceability Limit States............................................... 17 2.3 Modeling and Analysis for Drift Design .......................................................... 18 2.3.1 Sources of Deformation ............................................................................ 20 2.3.2 Modeling the Beam-Column Joint Region ............................................... 24 2.3.3 Connection Flexibility .............................................................................. 29 2.3.4 Composite Action ..................................................................................... 31 2.3.4.1 Floor Diaphragms ................................................................................. 33 2.3.5 Nonstructural Components ....................................................................... 35 2.3.5.1 Nonstructural Walls ............................................................................ 36 2.3.5.2 Cladding.............................................................................................. 38 2.3.6 Foundation Stiffness Flexibility................................................................ 39 2.3.7 Second Order (P-Delta) Effects ................................................................ 40 2.3.8 Structural Optimization.................................................................................... 42 2.4 Wind Loads....................................................................................................... 43 2.4.1 Factors Affecting Design Wind Loads ..................................................... 44 2.4.1.1 Mean Recurrence Interval................................................................... 44 2.4.1.2 Wind Velocity..................................................................................... 48 2.4.1.3 Topography and Roughness of the Surrounding Terrain.................... 49 2.4.1.4 Wind Directionality ............................................................................ 49 2.4.1.5 The Buildings Dynamic Characteristics ............................................. 50 2.4.1.6 Building Shape.................................................................................... 50 2.4.1.7 Shielding (Interference) Effects.......................................................... 50 2.4.2 Code Determined Wind Loads.................................................................. 51 2.4.3 Code Comparisons.................................................................................... 52 2.4.4 Wind Tunnel Testing ................................................................................ 53 2.4.4.1 Rigid Pressure Model............................................................................ 55 2.4.4.2 Rigid High Frequency Force Balance Models...................................... 55 2.4.4.3 Aeroelastic Models ............................................................................... 56
  5. 5. v 2.4.5 Database Assisted Design......................................................................... 56 2.4.6 Computational Fluid Dynamics................................................................ 57 2.5 Building Response ............................................................................................ 58 2.5.1 Methods of Measuring Response.............................................................. 59 2.5.1.1 Real Time Kinematic Global Positioning System (GPS) ..................... 59 2.5.2 Boundary Layer Wind Tunnel vs. Full Scale Comparisons ..................... 59 2.5.2.1 High-rise Buildings............................................................................... 61 2.5.2.2 Low-rise Buildings................................................................................ 65 2.6 Summary........................................................................................................... 66 REFERENCES ............................................................................................................. 69 Chapter 3: Test Building Modeling and Analysis........................................................ 79 3.1 Overview........................................................................................................... 79 3.2 Test Building: Structural System...................................................................... 79 3.2.1 Computer Software................................................................................... 80 3.3 Lateral Loads ........................................................