An Overview of Wind Engineering Where Climate Meets Design - - PowerPoint PPT Presentation

www.rwdi.com

• Presented by

Derek Kelly, M.Eng., P .Eng. Principal/Project Manager

An Overview of Wind Engineering Where Climate Meets Design

RWDI – Leadership & Consulting Expertise

RWDI ■ Consulting Engineers & Scientists

• ffering design guidance and

problem solving for structural and environmental issues ■ Established in 1972 ■ 440+ employees ■ Multi-disciplinary teams

• Senior scientists; engineers; specialists;

meteorologists; engineering technologists; technicians; support staff

Allied offices around the world

Overview

• Overall building aerodynamics
• Building motion and supplementary damping
• Snow drifting and loading

Instantaneous Pressure Distribution About a Building

Experimental Process

Planetary boundary layer and effect

• f surface roughness - mean velocity profile

Local wind climate assessment and distribution of wind speeds

0.1 1 10 100 1103 1104 20 40 60 80 100 120 Return Period (years) Mean hourly wind speed (mph)

\ bridge alignment included

0.01 0.1 1 10 100 P e rc e n ta g e o f Tim e 10 60 110 160 210 260 310 360 Wind Direction (degrees)

Winds Exceeding 90 mph

0.01 0.1 1 10 100 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 340 350 Bridge 0.01 0.1 1.0 10 100 1-year 10-year 100-year

Why we need shape optimization?

• 4.0E+09
• 2.0E+09

0.0E+00 2.0E+09 4.0E+09 B as e Ov ert urning M om ent (N -m ) 10 60 110 160 210 260 310 360 Wind Direction (degrees)

Mx

Wind Direction (degrees) Base Overturning Moment

Across-wind response where mean loads are negligible

Peak Maximum Mean Peak Minimum Along-wind response

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.

Why we need shape optimization?

• 4.0E+09
• 2.0E+09

0.0E+00 2.0E+09 4.0E+09 B as e Ov ert urning M om ent (N -m ) 10 60 110 160 210 260 310 360 Wind Direction (degrees)

Mx

Wind Direction (degrees) Along-wind response

Wind response can be significantly reduced by shape optimization.

Across-wind response where mean loads are negligible

Peak Maximum Mean Peak Minimum Base Overturning Moment

Across Wind Response and Vortex Shedding

12

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.

t B crit

S D f U 

D U S f

t



St= Strouhal number D = a characteristic dimension, taken as the width U = the velocity of the approaching wind

Strouhal Number

Mitigating Cross-Wind Response – 432 Park Avenue

Modified Original

25% - 30% REDUCTION IN BASE MOMENT Corner

• ptions

tested

Mitigating Cross-Wind Response – Taipei 101

15

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

Final Configuration

   ( ) ( . ) Max Min

2 2

06

Ref.Resultant

Reference

Configuration Test Date My (N-m) Ratio Mx (N-m) Ratio Ref. Resultant Ratio

Base (Tapered Box) 08/22/2008 5.45E+10 100% 4.98E+10 100% 6.22E+10 100% 100o (107o) 07/28/2008 4.53E+10 83% 4.19E+10 84% 5.18E+10 83% 110o (118o) 08/22/2008 3.97E+10 73% 4.31E+10 87% 4.92E+10 79% 180o (193o) 07/28/2008 3.39E+10 62% 3.65E+10 73% 4.18E+10 67% 120o (129o) - 0° Rot. Estimated 3.43E+10 63% 4.29E+10 86% 4.75E+10 76% 110o (118o) - 30° Rot. 09/29/2008 3.92E+10 72% 3.60E+10 72% 4.48E+10 72% 120o - 40° Rot. 09/29/2008 3.57E+10 66% 3.53E+10 71% 4.15E+10 67%

Assume the same structural properties for all configurations

(Vr=52m/s, 100-yr wind, damping=2.0%)

0° Rot. – Original 110° Shape Footprint Position 30° Rot. – Optimal Orientation of 110° Shape 40° Rot. – Optimal Orientation of 120° Shape

Benefits of Optimization due to Twist & Building Orientation Comparison of Base Overturning Moments

Controlling Motions

Taipei 101

Comcast Tower - Philadelphia

432 Park Avenue – in action!

Specialty Studies

Aeroelastic of a Super Tall Building

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

Aeroelastic Models of Completed Bridges

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

Aeroelastic scaling

Time and velocity scaling

b tU t

ref



*

Non-dimensional time = Non-dimensional velocity =

b U U

ref *

 

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, [m2/s]

• Often overlooked in bluff body aerodynamics for sharp edged objects
• Typical ranges at model scale Re values are 104
• Typical ranges at full scale Re values are 107

Reynolds Number Tests

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Drag coefficient

1E+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]

u b

A u CD

2 2 1

Force Drag  

4

2

b A   Plot of Drag Coefficient of a Cylinder vs. Reynolds Number

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.

High Reynolds Number Tests (option)

Example

High Reynolds Number Tests

High Reynolds Number Tests – Shanghai Center

• 2.00E+03

0.00E+00 2.00E+03 4.00E+03 6.00E+03 8.00E+03 1.00E+04 1.20E+04 1.40E+04 1.60E+04 1.80E+04 260 270 280 290 300 310 320 330 340 350 360

Shear Force (lbf) Wind Direction (degrees)

Fx

• 3.00E+04
• 2.50E+04
• 2.00E+04
• 1.50E+04
• 1.00E+04
• 5.00E+03

0.00E+00 5.00E+03 260 270 280 290 300 310 320 330 340 350 360

Shear Force (lbf) Wind Direction (degrees)

Fy Full Stage Equipment - Full Roof Full Stage Equipment - Half Roof No Stage Equipment - Full Roof No Stage Equipment - Half Roof

Wind Engineering Services – Scale Model Tests

Indiana State Fair Collapse Incident

• 2.00E+03

0.00E+00 2.00E+03 4.00E+03 6.00E+03 8.00E+03 1.00E+04 1.20E+04 1.40E+04 1.60E+04 1.80E+04 260 270 280 290 300 310 320 330 340 350 360

Shear Force (lbf) Wind Direction (degrees)

Fx

• 3.00E+04
• 2.50E+04
• 2.00E+04
• 1.50E+04
• 1.00E+04
• 5.00E+03

0.00E+00 5.00E+03 260 270 280 290 300 310 320 330 340 350 360

Shear Force (lbf) Wind Direction (degrees)

Fy Full Stage Equipment - Full Roof Full Stage Equipment - Half Roof No Stage Equipment - Full Roof No Stage Equipment - Half Roof

SNOW CONTROL FEATURES IN BUILDING DESIGN

Winter Winds Directionality (Blowing From) Toronto International Airport (1953-2015)

Percentage of Snow over All Winds: 12.9% Wind Speed km/h Probability (%) Winter Winds During Snowfall Blowing Snow 1-20 50.1 41.0 2.1 21-25 18.3 19.1 4.9 26-30 14.7 18.7 15.7 31-35 7.3 10.2 24.6 >35 5.5 8.2 52.8

All Winter Winds Winds during Snowfall Blowing Snow Events

Understanding the Local Climate

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

Drifting Snow in Urban Areas

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• Example Snow Drift

Simulation

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

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• Evaluation of Mitigation

Measures

Reduced Accumulations Large Structural Loads

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• Snow Drifts Pushed

Away from the Building Facade Wind Deflector Device

Evaluation of Mitigation Measures

Wind Deflectors above Clearstory Windows

Building Massing to Promote Controlled Sliding

Image Courtesy www.vikings.com

Large Catchment Gutter for Storing Sliding Snow Snow Deflector for Directing Snow into Large Catchment Gutter Sliding Snow and Ice

Building Massing to Promote Controlled Sliding

Image Courtesy www.vikings.com

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

Page 47

Reputation Resources Results

Canada | USA | UK | India | China www.rwdi.com

Example of Flow Fields Obtained from Wind Tunnel Testing

• 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

Velocity Vectors from Wind Tunnel Tests

Page 48

Reputation Resources Results

Canada | USA | UK | India | China www.rwdi.com

Example Time History of Minnesota Multi-Purpose Stadium Roof Loading for the Winter of 1981-1982 Example of Typical Roof Snow Accumulation for the Winter of 1981-1982 Example Time History of Ground Accumulation for the Winter of 1981-1982

Example of Roof Loading Pattern

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

MERCI BEAUCOUP