Strategies For Mitigating Wind-Induced Motion in Tall Buildings through Aerodynamic and Damping Modifications by Nnabuihe Nnamani B.Sc. in Civil & Environmental Engineering The George Washington University, 2011 Submitted to the Department of Civil & Environmental Engineering in Partial Fulfillment of the Requirements for the Degree of MASTER OF ENGINEERING IN CIVIL AND ENVIRONMENTAL ENGINEERING at the ASSACHUsETTs INSTrruTe Massachusetts Institute of Technology JUN 2 2 2'012 June 2012 © 2012 Massachusetts Institute of Technology LiB "RAR IE5 All rights reserved ARCHIVES Signature of Author: Department of Civil & Environmental Engineering May 18, 2012 Certified by: Jerome J. Connor Professor of Civil and Environmental Engineering Thesis Supervisor JI - 7A Accepted by II HeidiM. Nepf Chair, Departmental Committee for Graduate Students Strategies For Mitigating Wind-Induced Motion in Tall Buildings through Aerodynamic and Damping Modifications by Nnabuihe Nnamani Submitted to the Department of Civil & Environmental Engineering on May 18, 2012 in Partial Fulfillment of the Requirements for the Degree of Master of Engineering in Civil and Environmental Engineering ABSTRACT The advent of modern structural systems, spurred by advances in construction methodology and high strength materials, has driven the height of modern skyscrapers beyond what was once deemed possible. Although science and technology has been able to increase the strength of building materials such as steel and concrete, their material stiffness has remained virtually unchanged. The end result is a wave of taller, slender and more flexible skyscrapers that are very susceptible to wind-induced excitations. Ever mindful of the fact that human comfort levels are affected by perceived structural responses, engineers must employ various strategies to satisfy serviceability constraints. This thesis presents an overview, in addition to successful applications, of the various aerodynamic and damping modifications that are used to control wind-induced motion in tall buildings. Finally, a modified gyrostabilizer, akin to those used in luxury yachts, is proposed as a possible active control mechanism. The feasibility of this device was studied using simple statics and rigid body dynamics. Thesis Supervisor: Jerome J. Connor Title: Professor of Civil and Environmental Engineering ACKNOWLEDGEMENT I owe my deepest gratitude to my parents and family for being such as inspiration to me. I am very grateful for their trust, guidance and support in all my endeavors. I would also like to thank my thesis supervisor, Professor Jerome J. Connor, for his contributions and guidance throughout my research. Finally, I would like to acknowledge the Master of Engineering class of 2012 for their companionship throughout my time at MIT. I consider it a great pleasure to have had you all as classmates. 3 TABLE OF CONTENT A BSTRACT ................................................................................................................................................ 2 A CKN OW LEDG EM ENT ........................................................................................................................... 3 TA BLE O F CO N TENT .............................................................................................................................. 4 LIST O F FIGU RES ..................................................................................................................................... 5 INTRO D U CTIO N ...................................................................................................................................... 6 CH A PTER 1: W IN D IND U CED M OTION ........................................................................................ 9 DETERM IN ING W IND ................................................................................................................... 9 DETERMINING WIND LOAD AND STRUCTURAL RESPONSE.................................................... 10 W ind Tunnel Testing...................................................................................................................................11 Com putational Fluid Dynam ics ......................................................................................................... 12 CHAPTER 2: AERODYNAMIC MODIFICATIONS ...................................................................... 13 TAPERED CROSS SECTIONS AND SETBACKSA.CRO.E.T.I.NT.P.E.R.E.D.SS.SS..................................................... ........ 13 H ELICA L SHAPES ............................................................................................................................................... 15 ADDITION OF OPENINGS ................................................................................................................................ 16 CORNER M ODIFICATIONS ............................................................................................................................. 17 CHAPTER 3: SUPPLEMENTARY DAMPING MODIFICATION............................................... 20 PASSIVE DAM PING ............................................................................................................................................ 22 Tuned M ass Dam pers ................................................................................................................................. 22 Viscous and Viscoelastic Dam pers ................................................................................................... 25 ACTIVE DAM PING .............................................................................................................................................. 27 Active M ass Driver.......................................................................................................................................27 Hybrid M ass Dam per .................................................................................................................................. 28 SEM I ACTIVE DAM PERSS.................................................................................................................................. 29 M agneto-rheological (M R) dam per ................................................................................................ 29 Electro-rheological Dam per.....................................................................................................................31 Active Variable Stiffness ............................................................................................................................ 31 CHAPTER 4: PROPOSED DAMPING MODIFICATION ........................................................... 33 GYROSTABILIZER .............................................................................................................................................. 33 UN DERSTANDDER T NS IN G GYROSCOPIC .............................................................................................. 34 CON CEIVA BLE DESIGN .................................................................................................................................... 37 M echanism of a Gyroscope Attached to an exterior w all............................................................40 W ind loading on M odel..............................................................................................................................43 M odified Gyrostabilizer Design .............................................................................................................. 44 CONCLUSION ......................................................................................................................................... 48 REFERENCES ......................................................................................................................................... 50 4 LIST OF FIGURES Figure 1: Effects of Perceived Accelerations in Humans...........................................7 Figure 2: Patterns of w ind m otion................................................................................ 9 Figure 3: Vertical W ind Profile.................................................................................. 10 Figure 4: Chicago's Trump Tower in Wind Tunnel...................................................11 Figure 5: Burj Khalifa in Dubai, UAE........................................................................... 13 Figure 6: Proposed Kingdom Tower in Jeddah, Saudi Arabia.................14 Figure 7: Infinity Tow er in Dubai, UAE...................................................................... 15 Figure 8: Shanghai Tower in Shanghai, China............................................................16 Figure 9: Shanghai W orld Financial Center................................................................ 17 Figure 10: Various Corner Modifications.................................................................. 17 Figure 11: T aip ei 101 .................................................................................................. 18 Figure 12: Aqua Tow er in Chicago, USA.................................................................... 19 Figure 13: Undamped Response (left) and Damped Response (right)...................20 F ig u re 14 : T M D ................................................................................................................. 2 2 Figure 15: Pendulum TM D in Taipei 101.......................................................................23 Figure 16: Sliding