wind-induced response of structures using wind tunnel...

S. M. Zia Uddin1

Wind-induced Response Of Structures Using Wind Tunnel Model Test

Organized by: In collaboration with: Supported by:

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Failure of Tacoma Narrows Bridge on November 7, 1940 in UnitedStates caused by a 19 m/s wind speed

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Failure of a 50 meter tall billboard structure on 26 June 2002 inBangkok, Thailand

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Failure of 80 meter tall wind turbine on 2nd January 2015 inNorthern Ireland

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47.8 meter tall 5-story Shiten’noji Pagoda collapsed on September21, 1934 in Japan. The maximum wind speed was estimated to bemore than 60m/s.

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The upper-floor occupants of 240 meter tall 60-story John HancockTower suffered from motion sickness when the building swayed inthe wind. Tuned mass dampers and diagonal steel bracing wereinstalled to stabilize the movement.

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Importance of

Wind Load

Building Height

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Wind-induced Response Of Structures

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Wind-induced Overall Response Of Structures

time time

𝑋𝑡𝐹𝑡

time

𝑋𝑡

Overall response = Mean response + Background response + Resonant response

Inertial force

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Wind-induced Force

Wind-induced Response Prediction

Building Code Approach Wind Tunnel Model Test

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Building Code Approach

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Building Code Approach: ASCE/SEI 7-10

Design Wind Pressure, P = 𝑞 𝐺𝑓 𝐶𝑝 − 𝑞𝑖 𝐺𝐶𝑝𝑖

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Building Code Approach: ASCE/SEI 7-10

Design Wind Pressure, P = 𝑞 𝐺𝑓 𝐶𝑝 − 𝑞𝑖 𝐺𝐶𝑝𝑖

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Wind-induced Force

Wind-induced Response Prediction

Building Code Approach Wind Tunnel Model Test

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ASCE/SEI 7-10 vs Wind Tunnel Model Test

Mx My

Pe

ak

Ba

se M

om

en

t

Comparison of Peak Base Moment

ASCE

Wind Tunnel

Wind Tunnel = 1.35 x ASCE

Wind Tunnel = 1.59 x ASCE

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Limitations Of ASCE/SEI 7-10

Wind

Exposure D

Wind

Exposure C

Wind

Exposure B

• ASCE/SEI 7-10 do not account for interference effects caused by nearby buildings and other obstructions.

Y

X

Z

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Interference Effect

• Reduce mean response

time

𝑋𝑡

• Increase background and resonant response

• Increase overall response

Overall response = Mean response + Background response + Resonant response

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Interference Effect

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Wind Tunnel Model Test

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TU-AIT Boundary Layer Wind Tunnel Laboratory

• 23m X 2.5m X 2.5m

• Open-circuit, Blowing Type

• Test Section: 18.5m X 2.5m X 2.5m

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Boundary Layer Wind Profile

0

20

40

60

80

100

120

140

160

180

200

0 0.2 0.4 0.6 0.8 1 1.2

Mean Wind Speed Prof i le

Open-terrain

Suburban

Urban

Full Scale Height, m

𝑼𝒊 𝑼𝒊𝒓𝒆𝒇

=𝒊

𝒊𝒓𝒆𝒇

𝝎

Power Law,

0

20

40

60

80

100

120

140

160

180

200

0 0.1 0.2 0.3 0.4 0.5

Turbulence Intensity Prof i le

Open terrain

Suburban

Urban

Full Scale Height, m

𝑰𝒖𝒊 =𝟎. 𝟒 𝜷

𝒍𝒏𝒊𝒊𝟎

Longitudinal Turbulence Intensity,

Normalized Mean Wind Speed, 𝑼𝒊 𝑼𝒈

Longitudinal Turbulence Intensity, 𝑰𝒖𝒊

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Boundary Layer Wind Simulation

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0

20

40

60

80

100

120

140

160

180

200

0 0.2 0.4 0.6 0.8 1 1.2


Open-terrain

Suburban

Urban

0

20

40

60

80

100

120

140

160

180

200

0 0.2 0.4 0.6 0.8 1 1.2


Open-terrain

Suburban

Urban


Full Scale Height, mLength Scale=1:300

𝑼𝒊 𝑼𝒊𝒓𝒆𝒇

=𝒊

𝒊𝒓𝒆𝒇

𝝎

Power Law,

Normalized Mean Wind Speed, 𝑼𝒊 𝑼𝒈

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0

20

40

60

80

100

120

140

160

180

200

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5


Open terrain

Suburban

Urban



Open terrain

Suburban

Urban


Full Scale Height, mLength Scale=1:300

𝑰𝒖𝒊 =𝟎. 𝟒 𝜷

𝒍𝒏𝒊𝒊𝟎


𝑰𝒖𝒊 =𝝈𝒖𝒊 𝑼𝒊

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Wind-induced Force Measurement


High Frequency Force Balance (HFFB) Technique

High Frequency Pressure Integration (HFPI) Technique

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144 m48 cm

1:300 Scale

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AA

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Basic Parameters

𝐿𝑒𝑛𝑔𝑡ℎ 𝑆𝑐𝑎𝑙𝑒, 𝜆𝐿 = 𝐿𝑚𝐿𝑃= 1/300

𝑉𝑒𝑙𝑜𝑐𝑖𝑡𝑦 𝑆𝑐𝑎𝑙𝑒, 𝜆𝑉 = 𝑈𝑚 𝑈𝑃= 6.5/49

𝑇𝑖𝑚𝑒 𝑆𝑐𝑎𝑙𝑒, 𝜆𝑇 = 𝜆𝐿𝜆𝑉

𝑇𝑒𝑠𝑡 𝐷𝑢𝑟𝑎𝑡𝑖𝑜𝑛, 𝑇𝑚 = 𝜆𝑇 ∗ 3600Prototype Pressure: 𝑷𝑷𝒊𝒋

𝒕 = 𝑪𝒑𝒊𝒋𝒕 ∗

𝟏

𝟐𝝆 𝑼𝑷

𝟐

Time−Varying Pressure Coefficient: 𝑪𝒑𝒊𝒋𝒕 =

𝑷𝒎𝒊𝒋𝒕

𝟏𝟐𝝆 𝑼𝒎

𝟐

𝒊 = 𝟏𝟎, 𝒋 = 𝟐

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Modal Drag Force:

𝑄𝑘𝑥𝑡 =

𝑖=1

𝑁

𝐹𝑖𝑥𝑡 𝛷𝑖𝑘𝑥

Drag Force:

𝐹𝑖𝑥𝑡 =

𝑗=1

𝑛𝑖

𝑃𝑃𝑖𝑗𝑡 𝐴𝑃𝑖𝑗𝑥

𝑻𝒊𝒎𝒆

𝑸𝟏𝒙𝒕

0 degree wind direction

𝑸𝟏𝒙

𝑭𝒓𝒆𝒒𝒖𝒆𝒏𝒄𝒚, 𝒇𝒑 = 𝒇𝒎 ∗ 𝝀𝑻

𝒇 𝑺𝒒𝟏𝒙𝒎𝒇

0 degree wind direction

𝑿𝒊𝟏𝒙 = 𝑸𝟏𝒙𝑲𝟏𝒙

𝛷𝑖𝑘𝑥

Mean Displacement Response,

𝒇 𝑺𝒙𝟏𝒙𝒎𝒇

Fluctuating Wind Force

𝝈𝑩𝟏𝒙𝒎𝟐

𝝈𝑹𝟏𝒙𝒎𝟐

Inertial force

Modal Response Spectrum : 𝑺𝒙𝟏𝒙𝒎𝒇

=𝑺𝒒𝟏𝒙𝒎𝒇

𝑲𝟏𝒙𝟐

𝑯𝟏𝒙𝒇 𝟐

𝝈𝑩𝒊𝟏𝒙𝟐 = 𝜱𝒊𝟏𝒙

𝟐 𝝈𝑩𝟏𝒙𝒎𝟐

Background Displacement Response,

𝝈𝑹𝒊𝟏𝒙𝟐 = 𝜱𝒊𝟏𝒙

𝟐 𝝈𝑹𝟏𝒙𝒎𝟐

Resonant Displacement Response,

𝑿𝑫𝒊𝟏𝒙 = 𝑿𝒊𝟏𝒙 + 𝝈𝒙𝒊𝟏𝒙

Total Displacement Response,

𝝈𝒙𝒊𝟏𝒙 = 𝒈𝐵1𝑥𝟐 𝝈𝑩𝒊𝟏𝒙

𝟐 + 𝒈𝟏𝑅𝟐 𝝈𝑹𝒊𝟏𝒙

𝟐

Fluctuating Displacement Response,

Equivalent Static Drag Force,

𝑭𝑫𝒙 =𝑿𝑫𝒊𝟏𝒙 𝑿𝒊𝟏𝒙

𝑭𝑷𝒊𝒙

𝝈𝒒𝟏𝒙𝒎

𝒈𝑩𝟏𝒙𝝈𝒒𝟏𝒙𝒎

𝒈𝑩𝟏𝒙 = 𝑸𝟏𝒙𝒕 − 𝑸𝟏𝒙𝝈𝒒𝟏𝒙𝒎

𝒇 𝑺𝒒𝒊𝒙𝒎𝒇

𝒇 𝑺𝒙𝒊𝒙𝒎𝒇

0

20

40

60

80

100

120

140

160

-0.5 0 0.5 1 1.5H

eig

ht

(m)

Normalized Mode Shape

X direction

Y direction

Rotation

𝑄𝑘𝑥𝑡 =

𝑖=1

𝑁

𝐹𝑖𝑥𝑡 𝛷𝑖𝑘𝑥 +𝐹𝑖𝑦

𝑡 𝛷𝑖𝑘𝑦 + 𝐹𝑖Ɵ𝑡 𝛷𝑖𝑘Ɵ

𝑿𝑪 = 𝑿𝒊𝟏𝒙 + 𝑿𝒊𝟐𝒙 + 𝑿𝒊𝟑𝒙 + 𝒈𝑩𝟏𝑥𝟐 𝝈𝑩𝒊𝟏𝒙

𝟐 + 𝒈𝑩2𝑥𝟐 𝝈𝑩𝒊2𝑥

𝟐 + 𝒈𝑩3𝑥𝟐 𝝈𝑩𝒊𝟑𝒙

𝟐 + 𝒁𝑩𝟏𝒙𝟐𝒙 + 𝒁𝑩1𝑥𝟑𝒙 + 𝒁𝑩2𝑥𝟑𝒙 + 𝒈𝑹𝟏𝑥𝟐 𝝈𝑹𝒊𝟏𝒙

𝟐 + 𝒈𝑹2𝑥𝟐 𝝈𝑹𝒊𝟐𝒙

𝟐 + 𝒈𝑹3𝑥𝟐 𝝈𝑹𝒊𝟑𝒙

𝟐

Coupled Response : Equivalent Static Drag Force,

𝑭𝑫𝒙 =𝑿𝑪 𝑿𝑪 𝑭𝑷𝑪

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Design Wind Load Cases


𝑭𝑫𝒙 , 𝑭𝑫𝒚 ,𝑴𝑻Ɵ𝑭𝑫𝒚

𝑭𝑫𝒙𝑴𝑻Ɵ

𝟏𝟎𝟎%

𝟏𝟎𝟎%

𝟏𝟎𝟎% 𝟏𝟎𝟎%

𝟎%

𝟎%

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Design Wind Load Cases: Wind Tunnel Test

𝑭𝑿𝒕

𝑭Ɵ𝒕

( 𝑭𝒙 , 𝑭Ɵ)

( 𝑷𝒙 = 𝑭𝒙 𝑭𝒙= 𝟏)

( 𝑷Ɵ = 𝑭Ɵ 𝑭𝒙= 𝟎. 𝟔𝟐)

( 𝑷𝒙 = 𝑭𝒙 𝑭𝒙= 𝟏)

( 𝑷Ɵ = 𝑭Ɵ 𝑭𝒙= 𝟎. 𝟓𝟗)

Effective Equivalent Static Force (Mean),

𝑭𝒙 = 𝑷𝒙 𝑭𝑫𝒙

𝑭𝒚 = 𝑷𝒚 𝑭𝑫𝒚

𝑴Ɵ = 𝑷Ɵ𝑴𝑻Ɵ

𝑭𝒚

𝑭𝒙

𝑴Ɵ

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Design Wind Load Cases: ASCE/SEI 7-10

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𝒇𝐧 =𝟏

𝟐𝛑

𝐊

𝐌

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Wind

𝑭𝒙𝒕 (Drag force)

𝑴Ɵ𝒕 (Torsion)

𝑭𝒚𝒕 (Side force)

𝑿𝒊𝟏𝒙 = 𝑸𝟏𝒙𝑲𝟏𝒙

𝛷𝑖𝑘𝑥

Mean Displacement Response,

𝝈𝑩𝒊𝟏𝒙𝟐 = 𝜱𝒊𝟏𝒙

𝟐 𝝈𝑩𝟏𝒙𝒎𝟐

Background Displacement Response,

𝝈𝑹𝒊𝟏𝒙𝟐 = 𝜱𝒊𝟏𝒙

𝟐 𝝈𝑹𝟏𝒙𝒎𝟐

Resonant Displacement Response,

𝑿𝑫𝒊𝟏𝒙 = 𝑿𝒊𝟏𝒙 + 𝝈𝒙𝒊𝟏𝒙

Total Displacement Response,

𝝈𝒙𝒊𝟏𝒙 = 𝒈𝐵1𝑥𝟐 𝝈𝑩𝒊𝟏𝒙

𝟐 + 𝒈𝟏𝑅𝟐 𝝈𝑹𝒊𝟏𝒙

𝟐

Fluctuating Displacement Response,


𝑭𝑫𝒙 =𝑿𝑫𝒊𝟏𝒙 𝑿𝒊𝟏𝒙

𝑭𝑷𝒊𝒙

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Advantage Of High Frequency Pressure Integration (HFPI) Technique

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Wind

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Wind

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Importance of wind-induced response rises as structures grow taller and slender

Building codes have limited scope and many conditions

Wind tunnel model test provides appropriate wind-induced loading of structures

High Frequency Pressure Integration (HFPI) technique offers effective solution by outweighing disadvantages of High Frequency Force Balance (HFFB) technique

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wind-induced response of structures using wind tunnel...

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