Wind-Related Issues in the Design of Buildings · 2020. 3. 12. · derivation of wind loads and wind effects 2. Define the aerodynamic and meteorological variables involved in wind

Wind-Related Issues in the Design of Buildings

Copyright© 2018 by RWDI. All rights reserved.

WIND-RELATED ISSUES IN THE DESIGN OF BUILDINGS


This program is registered with AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product.

Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.


American Institute of Architects

This course provides a comprehensive review of wind related issues for high-rise buildings. Both derivation of overall structural wind loads and local wind loads for the design of cladding or building facades are discussed with emphasis placed on wind tunnel testing.

Abstract




1. Assess general methodologies and potential limitations included in building codes and standards for the derivation of wind loads and wind effects

2. Define the aerodynamic and meteorological variables involved in wind engineering.

3. Describe the potential benefits of alternative modeling and analytical approaches for the derivation of wind loads, specifically wind tunnel testing.

4. Evaluate potential mitigation strategies of real building project examples that have faced wind-related issues

Learning Objectives



Derek Kelly, P.Eng.

Senior Project Manager, Principal

Presented By

Derek is known for his ability to make exceptionally complex and demanding projects advance smoothly and without surprises. His keen communication skills, combined with his extensive experience in the design and construction of bridges and high-rise buildings, make him an invaluable leader on any project. Clients not only benefit from Derek’s mastery of project leadership skills from financial management to quality assurance, they enjoy the experience of collaborating with him as he steers their projects to successful conclusions.

1. Introduction to Wind Effects

2. Nature of Wind Speed• Effects of Local terrain

• Effects of Local climate

Agenda

3. Modelling the Building• Wind Load Studies

4. Influence of Shape• Structural Wind Load

Studies: Input And Output




Introduction to Wind Effects


Structural failure

Aeroelastic instability

Cladding failure

Pedestrian wind comfort

Serviceability or wind induced motion

Types of Risk from Wind



Flow Pattern and Pressure Distribution



Complex geometry

Interference of neighbouring buildings

Upwind terrain

Dynamic excitation

Building codes lack of resolution


Wind Load Assessment

Wind Tunnel Testing



Building Geometry

Wind Tunnel Testing

LocalClimate

Structural Properties

Wind Loads

LocalTerrain



Nature of Wind Speed



Nature of Wind Speed

25 m/s

20 m/s

15 m/s

10 m/s

5 m/s

1 min 2 min 3 min 4 min 5 min0 min

153 m

64 m

12 m


Vertical Profile of Wind Speed



Effects ofLocal Terrain



Surface Roughness

IncreasingRoughness


Wind Tunnel Profiles





Existing surroundings Future surroundings

Effect of Immediate Surroundings

Effects ofLocal Climate





Statistical analysis of wind conditions at a siteMost locations (Asia, North America, Western Europe) have useful data from local airports

Airports catalog:

• Location of instrumentation

• Height of anemometers or data acquisition equipment

• Averaging time of data acquisition equipment

Directionality of Local Wind Climate


Directionality of Local Wind Climate

Wind Speed

(mph)

Probability (%)

Summer Winter

Calm 8.1 6.2

1-5 16.7 13.4

6-10 48.6 38.9

11-15 21.9 28.3

16-20 4.0 10.2

>20 0.7 2.9

Summer (May – October) Winter (November - April)

Jackson Hartsfield International Airport (1983 - 2013)


Probability of Recurrence

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

1 10 100 1000 10000

Win

d S

pe

ed

(m

/s)

Mean Recurrence Interval (years)

Predicted Wind Speed Code Basic Wind Speed




Probability of Recurrence

0.0

50.0

100.0

150.0

200.0

250.0

300.0

1 10 100 1000 10000

Win

d S

pe

ed

(k

m/h

)

Mean Recurrence Interval (years)Extra-Tropical Extra-Tropical + Typhoon Code Basic Wind Speed


Wind Directionality

0

5

10

15

20

25

30

35

40

45

N10

20

30

40

50

60

70

80

E

100

110

120

130

140

150

160170

S190

200

210

220

230

240

250

260

W

280

290

300

310

320

330

340350

Design Winds

0

5

10

15

20

25

30

35

40

45

N10

20

30

40

50

60

70

80

E

100

110

120

130

140

150

160170

S190

200

210

220

230

240

250

260

W

280

290

300

310

320

330

340350

Design Winds

Beirut, Lebanon Taipei, Taiwan

Wind speed (m/s)

Mean Recurrence Interval of 50 years

Modelling The Building




Architect’s 3D Model

Wind Tunnel Models

RWDI’s 3D Model Physical Model


Wind LoadStudies


Cladding Wind Load Study

High Frequency Pressure Integration Study (HFPI)

High Frequency Force Balance Study (HFFB)

Common Types of Wind Loading

Assessment




Pressure Studies: Cladding &HFPI


Wind Tunnel Model Data Acquisition


In-House Software





Local peak pressures

for cladding design

Recommended even for short buildings

Typically lower than code




Wind pressure vs wind direction

Local Pressure Coefficient


Internal Pressure Considerations




Wind Pressure Block Diagrams

Negative Pressure (psf)

Wind Pressure Block Diagrams


ASCE 7 Standard

Condition Zone 4 (central zone)

Zone 5 (edge zone)

EnclosedBuilding

-32 -59

Open Condition

-43 -70

HFPI Structural Wind Load Study




HFPI Structural Wind Loads



Provides overall wind loads and wind-induced motion

Pros:

+ Includes higher order modes

+ Allows to include large podia

Cons:

- Requires simple geometry and sharp corners

- May take longer

HFPI Structural Wind Loads

HFFB Structural Wind Load Study





Force balance Wind tunnel model

HFFB Structural Wind Loads

Provides overall wind loads and wind-induced motion

Suitable for most geometries

Generally faster

Combines mean and dynamic wind loading


HFFB Structural Wind Loads


Base Wind Loads vs Wind Direction

0

5

10

15

20

25

30

35

40

45

N10

20

30

40

50

60

70

80

E

100

110

120

130

140

150

160170

S190

200

210

220

230

240

250

260

W

280

290

300

310

320

330

340350

Design Winds

Wind speed (m/s)



Worst-Case Overall Forces

Effective Static FBF Wind Loads

Design Wind Loads

Load Combination Factors



Aerodynamic response

Influence of the Wind Climate






Combination of response and directionality



Aerodynamic

Response

Wind Climate

Model

Combination of

Response and

Directionality


Peak response aligned with less frequent winds

Peak response aligned with prevailing winds

Code Analytical methods mostly address drag loading only

Lift is larger in both cases but ratio of lift / drag less in more built-up surroundings


Influence of Surroundings

Drag response

Direction of Loading



LIFT



Drag response

DRAG



Wake buffeting

-8E+07

-6E+07

-4E+07

-2E+07

0E+00

2E+07

4E+07

6E+07

Ba

se

To

rs

ion

al

Mo

me

nt

on

To

we

r C

(N

-m

)

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

Without Upstream Tower B With Upstream Tower B

N (0 deg.)

X

Y

WIND

Building codes are reliable for short, stiff buildings

Code might miss important dynamic effects on tall or unusual buildings

Wind Tunnel is always more accurate


Wind Tunnel vs Code Structural Wind Loads




Drag Loads include mean and dynamic component

Typical Tall Building - Drag

-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


Ba

se O

ve

rtu

rnin

g M

om

en

t

Peak MaximumMean

Peak Minimum

DRAG

WIND

Dir

ecti

on

of

Lo

ad

ing

Plan


Across-wind response where mean loads are negligible

Typical Tall Building – Lift

-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


Mx


Ba

se O

ve

rtu

rnin

g M

om

en

t

Peak MaximumMean

Peak Minimum

Dir

ecti

on

of

Lo

ad

ing

Plan

WIND

LIFT


Across-Wind Loading (Vortex Shedding)

Directions of fluctuating force

WIND




Across-Wind Loading (Vortex Shedding)

Shedding frequency N (Hz) is given by:

b

USN

S = Strouhal number

U = wind speed

b = building width

“N” can be related to building frequencies

“S” is function of building shape

Above gives indication whether Vortex Shedding

will impact strength and/or serviceability Wind velocity

Cro

ssw

ind

Re

spo

nse

Vortex shedding

No vortex shedding


Lift and Drag Spectra Comparison

0.001

0.01

0.1

1

10

0.001 0.01 0.1 1 10

fS/σ

^2

Reduced Frequency

0.001

0.01

0.1

1

10

0.001 0.01 0.1 1 10

fS/σ

^2

Reduced Frequency


Benefit of 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


Mx


Ba

se O

ve

rtu

rnin

g M

om

en

t

Peak MaximumMean

Peak Minimum

Dir

ecti

on

of

Lo

ad

ing

Plan

WIND



Influence of Shape


Across-Wind Response

UniformSection

Severe cross-windexcitation

SharpCorners


Across-Wind Response

Tapering

Severe cross-windexcitation

Porosity

AerodynamicSolutions

Corner Modifications




“We virtually designed [the tower] in a wind tunnel”

Bill Baker of Skidmore Owings & Merrill Discussing Dubai Project



432 Park Ave: Exploration of Openings

Initial wind tunnel model of 432 Park Avenue included a worst case baseline

432 Park Avenue with double story openings at five levels


Study of Exploration of Openings




“Softened” corners

Sensitivity to Corner Details

Slotted Corners Chamfered Corners



69

Tapered Box

100o Configuration

110o Configuration

120o Configuration 180o Configuration

SHANGHAI TOWER, CHINA - Final ConfigurationCopyright© 2018 by RWDI. All rights reserved.



Comparison of base overturning moments:


Benefits of Optimization: Twist and Building Orientation

Configuration Ratio

Base (Tapered Box) 100%

100o

(107o) 83%

110o (118

o) 79%

180o

(193o) 67%

120o

(129o) - 0° Rot. 71%

110o (118

o) - 30° Rot. 72%

120o - 40° Rot. 67%

Tapering and setbacks


Shaping Strategies

Varying cross-section shape

Spoilers Porosity or openings

“Softened” corners



“Hardened” cornersSlotted Corners Chamfered Corners Basic Fins




Exposed structure at edges – big response increase



Corner Modifications

Mitigation


Building Motions




Accelerations

Structural Wind Load Studies:Input And Output


• 3D model of the building or full drawing package

• Information on surrounding buildings

• Information on building code and return period

• Structural dynamic properties

• Assumed damping

• Maximum base reactions

• Floor-by-floor equivalent static wind loads

• Predicted accelerations and torsional velocities

• Sensitivity analysis of the above to damping, natural frequencies and mass


Structural Assessments

Input required



THANK YOUDerek Kelly, P.Eng.Building Performance [email protected]

RWDI.COM KNOWLEDGE LEARNING LAB


rwdi.com

Documents

Wind-Related Issues in the Design of Buildings · 2020. 3. 12. · derivation of wind loads and wind effects 2. Define the aerodynamic and meteorological variables involved in wind