an overview of wind engineering where climate meets design - rwdi philadelphia presen… · •...

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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 offering 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 of surface roughness - mean velocity profile

Local wind climate assessment and distribution of wind speeds

0.1 1 10 100 1 103 1 1040

20

40

60

80

100

120

Return Period (years)

Mea

n ho

urly

win

d sp

eed

(mph

)

\ bridge alignment included

0.01

0.1

1

10

100

Pe

rce

nta

ge

of

Tim

e

10 60 110 160 210 260 310 360Wind Direction (degrees)

Winds Exceeding 90 mph 0.01

0.1

1

10

100 0 10

2030

40

50

60

70

80

90

100

110

120

130

140150

160170180190

200210

220

230

240

250

260

270

280

290

300

310

320330

340350

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 O

ve

rtu

rnin

g M

om

en

t (N

-m)

10 60 110 160 210 260 310 360 Wind Direction (degrees)

Mx

Wind Direction (degrees)

Bas

e O

vert

urn

ing

Mo

men

t 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

Ba

se

Ov

ert

urn

ing

Mo

me

nt

(N-m

)

10 60 110 160 210 260 310 360 Wind Direction (degrees)

Mx


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

Bas

e O

vert

urn

ing

Mo

men

t

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

Bcrit

S

DfU

D

USf 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 options tested

Mitigating Cross-Wind Response – Taipei 101

15 15

Tapered Box

100o Configuration

110o Configuration

120o Configuration 180o Configuration

Final Configuration

( ) ( . )Max Min2 206Ref.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

tUt

ref*Non-dimensional time =

Non-dimensional velocity = b

UU

ref

0

*

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:

VDRe

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

Dra

g co

effic

ient

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

AuCD 2

21

Force Drag

4

2bA

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

She

ar F

orc

e (

lbf)


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

She

ar F

orc

e (

lbf)


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

She

ar F

orc

e (

lbf)


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

She

ar F

orc

e (

lbf)


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

www.rwdi.com



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

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

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

an overview of wind engineering where climate meets design - rwdi philadelphia presen… · •...

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