Relationship between importance of wind and height. Importance of wind loads. Council on Tall Buildings. and Urban Habitat.

Transcription

1

2 Relationship between importance of wind and height Importance of wind loads Building height

3 Growth of the tall building No. over 300 m Start of my career in wind engineering Year Formation of RWDI No. over 200 m Number Completed

4 The Megatall Building Wind engineering by RWDI

5 72 Story Bank of America Tower, Dallas Architect: HLM Design. Structural Engineers: Brockette Davies Drake / LeMessurier Consultants Aeroelastic Model used in wind tunnel tests. (early 1980 s)

6 wind Shedding frequency N is given by Directions of fluctuating force Vortex shedding N U S b S = Strouhal number U = wind speed b = building width

7 Peak response due to vortex excitation Magnitude of peak response density 1 damping

8 Metropolitan Tower and City Spire, NY Metropolitan Tower Architect: Schuman Lichtenstein Structural Engineer: Rosenwasser/Grossman Origin of the milli-g criterion. Considered using Tuned Mass Damper of pendulum type City Spire Architect: Murphy/ Jahn Structural Engineer: Rosenwasser/Grossman (Mid 1980 s)

9 Occupant Comfort Criteria Thou shalt use milli-g at the 10 year return period for a residence

10 Acceleration ( milli - g ) PREDICTED 10 YEAR ACCELERATIONS OF 19 BUILDINGS THAT HAVE BEHAVED SATISFACTORILY Upper point without SDS Lower point with SDS Building # milli-g range accelerations Above milli-g range accelerations Reduced acceleration responses using SDS SDS = Supplementary Damping System

11 Exploratory Studies on ½ Mile High Tower, Chicago Architect: Harry Weese Structural Engineer: Thornton Tomasetti (Late 1980 s)

12 Miglin Beitler, Skyneedle First of a few planned 2000ft buildings in Chicago. Architect: Cesar Pelli. Structural Engineer: Thornton Tomasetti. (Early 1990 s)

13 Petronas Towers Architect: Cesar Pelli Structural Engineer: Thornton Tomasetti (Early 1990 s)

14 Original Modified Taipei 101 Architect: C.Y. Lee Structural Engineers: Evergreen Engineers / Thornton Tomasetti 25% REDUCTION IN BASE MOMENT

15 Shape effect, Taipei 101 wind tunnel tests

16 Use of tuned mass damper Taipei 101 With TMD - 35% reduction in acceleration

17

18 TMD in operation.during Typhoon Longwang- October 2005

19 Park Tower, Random House and Wall Center with Damping Systems Chicago Vancouver New York

20 Trump world Tower and Bloomberg Center with Damping Systems New York New York

21 Buildings with Supplemental Damping System Building Number Building Name and Location SDS Type Installed 10-Year Peak Resultant Acceleration Without SDS ( milli g ) With SDS 1 Park Tower, Chicago, IL TMD Random House, New York, NY 12 Wall Centre, Vancouver, BC 18 Bloomberg Tower, New York, NY TLCD TLCD Trump World Tower, New York, NY TMD TMD

22 Burj Khalifa 828 m Architect and Structural Engineer: Skidmore Owings Merrill Set backs, changing cross-section, orientation Completed Building Early 1:500 scale wind tunnel tests

23 We virtually designed [the tower] in a wind tunnel Bill Baker of Skidmore Owings & Merrill discussing the Burj Khalifa Project

24 Shaping strategies Softened corners Tapering and setbacks Varying cross-section shape Spoilers Porosity or openings

25 1:50 Scale Model of Upper Portion of Burj Khalifa High Reynolds Number Tests, Re ~ 2x10 6 Note: Full scale Re~7x10 7

26 Meso-scale Modelling of June 1988 Event

27 Chicago Spire Very Long period Higher Mode Effects

28 Higher modes can affect response ~ questions re frequency dependent motion criteria such as ISO comfort criteria Height, m nd harmonic 1st harmonic Mode deflection shape

29 Chicago spire - motion and deflection control through use of damping system.

30 Assessing building motions. ISO Criteria for single frequency Moving room simulations of multiple frequencies Peak acceleration, milli-g Frequency, Hz

31 Shanghai Center 632 m Twisting and tapering Architect: Gensler Structural Engineers: Thornton Tomasetti

32 High Reynolds number tests on Shanghai Center Example of Mean Pressure Coefficients Pressure tap count

33 Nakheel Tower studies, m Architect: Woods Bagot Structural Engineer: WSP Cantor Seinuk (Early 2000 s)

34 Consequence of vortex shedding on reliability assessment Nakheel Tower Uncertainty in loads is mostly dictated by uncertainty in this peak Low ratio of 1000 year to 50 year loads Need to carefully assess uncertainty in peak vortex shedding response since the normal assumption that uncertainty in wind speed governs is no longer valid. Damping and frequency uncertainties become important.

35 432 Park Avenue, NY, 16:1 slenderness ratio August 2014 Architect: Raphael Vinoly Structural Engineer: WSP Cantor Seinuk Wind Tunnel Model

36 Future of wind engineering of tall buildings Current methods of structural design are based on linear elastic analysis. Indications are that this results in them having much more reserve strength for wind than earthquake. There could be benefits from examining the non-linear response under extreme winds Could tall buildings be useful as hurricane/typhoon shelters. Occupants would not need to evacuate. High-rise buildings seem to be inherently superior when it comes to storm surge. Critical services (emergency power, water, waste systems) can be designed to be above storm surge and keep the building self sufficient during the event and for a period afterwards. The weak link in wind resistance appears to be the building envelope. The envelope is also key to developing greener buildings. Therefore this is an area where there is ample room for new developments in design, performance testing and creativity.

37 Thank you.