An Overview of Wind Engineering Where Climate Meets Design

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1 An Overview of Wind Engineering Where Climate Meets Design Presented by Derek Kelly, M.Eng., P.Eng. Principal/Project Manager

RWDI Leadership & Consulting Expertise RWDI Consulting Engineers & Scientists offering design guidance and problem solving for structural and environmental issues

2 RWDI Leadership & Consulting Expertise RWDI Consulting Engineers & Scientists offering design guidance and problem solving for structural and environmental issues Established in employees Multi-disciplinary teams Senior scientists; engineers; specialists; meteorologists; engineering technologists; technicians; support staff

3 Allied offices around the world

4 Overview Overall building aerodynamics Building motion and supplementary damping Snow drifting and loading

5 Instantaneous Pressure Distribution About a Building

6 Experimental Process

7 Planetary boundary layer and effect of surface roughness - mean velocity profile

9 Local wind climate assessment and distribution of wind speeds Mean hourly wind speed (mph) \ bridge alignment included year Bridge P e rc e n ta g e o f Ti m e Return Period (years) 100-year Winds Exceeding 90 mph Wind Direction (degrees) year

10 Why we need shape optimization? Across-wind response where mean loads are negligible Mx 4.0E+ 09 Base Overturning Moment B a s e O v e rt u r n in g M o m e n t ( N -m ) 2.0E E E E+ 09 Along-wind response Wind Direction (degrees) Wind Direction (degrees) Peak Maximum Mean Peak Minimum For a slender tall building with almost uniform cross-section, the wind loads can be governed by across-wind response due to vortex shedding. This normally becomes an issue for both strength design and serviceability.

11 Why we need shape optimization? Across-wind response where mean loads are negligible Mx 4.0E+ 09 Base Overturning Moment B a s e O v e rt u r n in g M o m e n t ( N -m ) 2.0E E E E+ 09 Along-wind response Wind Direction (degrees) Wind Direction (degrees) Peak Maximum Mean Peak Minimum Wind response can be significantly reduced by shape optimization.

12 Across Wind Response and Vortex Shedding Strouhal Number f S U t D S t = Strouhal number D = a characteristic dimension, taken as the width U = the velocity of the approaching wind Strouhal numbers have been determined for a variety of shapes such as rectangular, circular and triangular bodies. Typically between 0.12 to 0.16 for squared objects, and 0.2 to 0.22 for circular bodies. U crit f B S D t 12

13 Mitigating Cross-Wind Response 432 Park Avenue

14 Mitigating Cross-Wind Response Taipei 101 Original Corner options tested Modified 25% - 30% REDUCTION IN BASE MOMENT

15 Tapered Box 120 o Configuration 180 o Configuration 100 o Configuration 110 o Configuration 15 Final 15 Configuration

16 Benefits of Optimization due to Twist & Building Orientation Comparison of Base Overturning Moments Assume the same structural properties for all configurations (Vr=52m/s, 100-yr wind, damping=2.0%) Reference Configuration Test Date My (N-m) Ratio Mx (N-m) Ratio Ref. Ratio Resultant Base (Tapered Box) 08/22/ E % 4.98E % 6.22E % 100 o (107 o ) 07/28/ E+10 83% 4.19E+10 84% 5.18E+10 83% 110 o (118 o ) 08/22/ E+10 73% 4.31E+10 87% 4.92E+10 79% 180 o (193 o ) 07/28/ E+10 62% 3.65E+10 73% 4.18E+10 67% 120 o (129 o ) - 0 Rot. Estimated 3.43E+10 63% 4.29E+10 86% 4.75E+10 76% 110 o (118 o ) - 30 Rot. 09/29/ E+10 72% 3.60E+10 72% 4.48E+10 72% 120 o - 40 Rot. 09/29/ E+10 66% 3.53E+10 71% 4.15E+10 67% Ref.Resultant 0 Rot. Original 110 Shape Footprint Position 30 Rot. Optimal Orientation of 110 Shape 40 Rot. Optimal Orientation of 120 Shape ( Max) ( 0. 6 Min) 2 2

17 Controlling Motions

18 Taipei 101

19 Comcast Tower - Philadelphia

20 432 Park Avenue in action!

21 Specialty Studies

22 Aeroelastic of a Super Tall Building

23 Aeroelastic model of a construction stage Image of a Rigid Aeroelastic Model Under Construction

24 Aeroelastic Models of Completed Bridges Tacoma Narrows Bridges Tacoma, Washington (suspension bridges) Cooper River Bridge - Charleston, S.C. (cable-stayed bridge)

25 Aeroelastic scaling

26 Non-dimensional time = Time and velocity scaling Non-dimensional velocity = t * U tu * b ref U ref b 0

27 Reynolds Number Tests In fluid mechanics, the Reynolds number is a measure of the ratio of inertial forces to viscous forces, and quantifies the relative importance of these two types of forces for given flow conditions. It is primarily used to identify different flow regimes passing by a given object. Typically, Reynolds number is defined as follows: VD Re where: V - mean fluid velocity, [m/s] D - diameter of pipe, [m] ν - kinematic fluid viscosity, [m 2 /s] Often overlooked in bluff body aerodynamics for sharp edged objects Typical ranges at model scale Re values are 10 4 Typical ranges at full scale Re values are 10 7

28 Plot of Drag Coefficient of a Cylinder vs. Reynolds Number 4.0 Drag coefficient u b Drag Force 1 u A C D 2 2 A b E+01 1E+02 1E+03 1E+04 1E+05 1E+06 1E+07 Reynolds number [After Clift, Grace and Weber Bubbles, Drops and Particles, Academic Press, 1978]

29 Addressing Reynolds Number Because the Reynolds number is a function of Speed, Width of the object, and viscosity, one can do the following to achieve a high Reynolds number: Test a large model Test at a high speed Change the air density in the experiment* *difficult to do, need a pressurized wind tunnel For projects that RWDI has worked, a large model has been built and tested at a high speed. These experiments are then compared to a similar experiment conducted at a smaller scale in RWDI s facilities. The results from each are then compared to original wind tunnel tests. The outcome is typically the overall responses, i.e. overall loads on a tower and building accelerations reduce, whereas the local Cladding loads may increase slightly and the distribution will change.

30 High Reynolds Number Tests (option) Example

31 High Reynolds Number Tests

32 High Reynolds Number Tests Shanghai Center

33 Shear Force (lbf) Fx 1.80E E E E E E E E E E E Wind Direction (degrees) Full Stage Equipment - Full Roof No Stage Equipment - Full Roof Shear Force (lbf) 5.00E+03 Fy 0.00E E E E E E E Wind Direction (degrees) Full Stage Equipment - Half Roof No Stage Equipment - Half Roof

34 Indiana State Fair Collapse Incident Wind Engineering Services Scale Model Tests

Shear Force (lbf) Fx 1.80E+04 1.60E+04 1.40E+04 1.20E+04 1.00E+04 8.00E+03 6.00E+03 4.00E+03 2.00E+03 0.00E+00-2.

35 Shear Force (lbf) Fx 1.80E E E E E E E E E E E Wind Direction (degrees) Full Stage Equipment - Full Roof No Stage Equipment - Full Roof Shear Force (lbf) 5.00E+03 Fy 0.00E E E E E E E Wind Direction (degrees) Full Stage Equipment - Half Roof No Stage Equipment - Half Roof

36 SNOW CONTROL FEATURES IN BUILDING DESIGN

9% Wind Speed km/h Winter Winds Probability (%) During Snowfall Blowing Snow 1-20 50.1 41.0 2.

37 Understanding the Local Climate All Winter Winds Winds during Snowfall Percentage of Snow over All Winds: 12.9% Wind Speed km/h Winter Winds Probability (%) During Snowfall Blowing Snow > Blowing Snow Events Winter Winds Directionality (Blowing From) Toronto International Airport ( )

38 Site surroundings and topography also something we also have little control over

39 Drifting Snow in Urban Areas

40 Unbalanced Structural Snow Load Approaching Wind Flow Large Problematic Grade Level Drift Roof Step Accumulation Example Snow Drift Simulation

41 Reduced Accumulations Large Structural Loads Evaluation of Mitigation Measures

42 Snow Drifts Pushed Away from the Building Facade Wind Deflector Device Evaluation of Mitigation Measures

43 Wind Deflectors above Clearstory Windows

44 Building Massing to Promote Controlled Sliding Image Courtesy

45 Large Catchment Gutter for Storing Sliding Snow Sliding Snow and Ice Snow Deflector for Directing Snow into Large Catchment Gutter Building Massing to Promote Controlled Sliding Image Courtesy

46 Scale Model of Minnesota Multi-Purpose Stadium in RWDI s Boundary Layer Wind Tunnel

Reputation Resources Results Canada USA UK India China www.rwdi.

47 Reputation Resources Results Canada USA UK India China Velocity Vectors from Wind Tunnel Tests RWDI s FAE (Finite Area Element) study was used to derive detailed snow loading patterns on the roof for 58 years of historical winter weather data The study accounted for: snow and rainfall on the roof the velocity field (drifting) across the roof thermal effects or heat loss sliding Page 47 Example of Flow Fields Obtained from Wind Tunnel Testing

the Winter of 1981-1982 Example Time History of Minnesota Multi-Purpose Stadium Roof

48 Reputation Resources Results Canada USA UK India China Example of Roof Loading Pattern Example Time History of Ground Accumulation for the Winter of Example Time History of Minnesota Multi-Purpose Stadium Roof Loading for the Winter of Example of Typical Roof Snow Accumulation for the Winter of Page 48

49 Through knowledge and understanding, we can anticipate and control the impact of the climate in the built environment. Performance and precision.

50 MERCI BEAUCOUP

RESILIENT INFRASTRUCTURE June 1 4, 2016

RESILIENT INFRASTRUCTURE June 1 4, 2016 CASE STUDIES ON THE IMPACT OF SURROUNDING BUILDINGS ON WIND-INDUCED RESPONSE John Kilpatrick Rowan Williams Davies and Irwin, Guelph, Ontario, Canada ABSTRACT In