Wind Generated Structural Response of Tall Buildings

Rakibul Hasan Meseret Kahsay Dan Parvu Joshua Rosenkrantz Zeinab Samani Tong Zhang

May 3, 2023

Given Parameters & Requirements

Building Geometric and Structural PropertiesBuilding Height (H) 90 m

Building Width (W) 40 mBuilding Depth (D) 35m

Mass / Volume 110kg/m3

Damping Ratio 0.01

0.015

ExposureOpen

SuburbUrban

Return Period 50 Years (ULS) 10 Years (SLS)Design Code NBCC 2005

• Design Wind Speed Gumbel Distribution

• Dynamic Procedure Vibrationally Sensitive

• Objective of Analysis:

• Reduce the structural response to be less than acceptable values

• Minimize the cost and scope of recommended changes.

Objectives and Methodology

Wind Profile

Wind Profile

18.9 m/s

26 m/s

28.5 m/s

Assumptions

Building Use CommercialConstruction Reinforced Concrete Shear

WallVibrationally Sensitive? Yes:

• Tall Structure• Exposed to Mechanical

Vibrations from A/C

Analysis Procedure

q : design wind pressure Ce : Exposure factor Cg : Gust factor Cp : Pressure coefficient

Calculation of External Design Pressure

Ce windward H=90 mCe leeward H=45 m

Cp was found by using fig. I-15 and H/D≥1Where h=90 m and D= 35 m

External pressure coefficient

Cpw (windward) 0.8Cpl (leeward) -0.5

K: Surface roughness factorB: Background turbulence factorS: Size reduction factorF: Gust energy ratiogp: Peak factor fn: Natural frequency (Type of the building: Concrete)

Calculation of Gust factor

External design Pressure

Reference wind speed: V10 = 22.56 m/s , V50 = 26 m/s

Base Moment, Displacement, Acceleration

Results

Exposure Open terrain Suburban terrain Urban terrainBuilding Height (H) 90 (m) 90 (m) 90 (m)Building Width (W) 40 (m) 40 (m) 40 (m)Building Depth (D) 35 (m) 35 (m) 35 (m)Building Density (ρB) 110 (kg/m3) 110 (kg/m3) 110 (kg/m3)Damping Ratio ( β ) 0.01 0.015 0.01 0.015 0.01 0.015Reference Wind Speed (V50) 26 (m/s) 26 (m/s) 26 (m/s)Reference Wind Speed (V10) 22.56 (m/s) 22.56 (m/s) 22.56 (m/s)Net Pressure 1824.2 1760.8 1408.0 1356.5 962.7 945.6Wind Velocity at H (VH) 28.48 (m/s) 26.08 18.90Gust Factor Windward, Cg 1.84 1.77 2.06 1.99 2.24 2.20Base bending moment (KN· m) 240263 231904 176817 170353 111395 109417Displacement (m) 0.050 0.049 0.038 0.037 0.027 0.026Acceleration (m/s2) 0.250 0.204 0.209 0.171 0.113 0.092

• To effectively reduce the along-wind structural response of the building, measures must be taken by:

• Decreasing the surface area of the structure perpendicular to the direction of wind,

• Increasing the damping ratio, and

• Increasing the building density.

Mitigation of Excessive Response

• Wind confusion

• Limiting the amount of surface area perpendicular wind along height

• Absolute World Tower has a twisting, elliptical plan

Mitigation of Excessive Response

• Dampers

• Sloshing-action of a tuned liquid damper

• Counter-weight action of a tuned mass damper• eg. Taipei 101 Damper

Mitigation of Excessive Response

• Building Density

• Density is inversely proportional to building response

Mitigation of Excessive Response

• Increase building density• Comparably lower costs• Least change of scope

Recomendation

Thank You