7/31/2019 Wind load analysis By UBC for Tall buildings - Tall Buildings

1/3

Assignment No. 1: Wind Load Analysis by UBC Tall Buildings

Assignment No.1 (Wind load analysis By UBC) By Afzal Waseem for Ryerson

University

Data on Design Problem (Wind load analysis)

My Serial No = 33

Nature of Building: Hospital BuildingStories: 15 + 33 = 48 Stories

Exposure condition: open terrain

Scattered obstructions but also includes shoreline in hurricane prone region

Typical story height: 10ft (3.05m)

2 Bottom floors height: 15ft (4.6m)

Building height: (2x15) + (46x10) = 490 ft (149.4 m)

Basic wind speed V = 100 mph

Building width = 80 ft

Design wind pressures and floor by floor lateral force for lateral load analysis of the building.Find the wind load distribution and the total base shear. (USE UBC)

DESIGN

The Uniform Building Code is a Static method that assumes the building to be a fixed rigid body

in the wind. This method is appropriate for mid-sized buildings, which are neither particularly

slender nor susceptible to vibrations under high winds

Design wind pressure p is obtained from formula:

Ce = a coefficient that accounts for the combined effects of height, exposure and gusting;

Cq = a coefficient that allowing for higher pressures for wall and roof elements; for example, C q

has a value of 1.4 when using the projected area method of calculating the wind loading for

structures over 40 ft in height, whereas it has a local value of 2.0 at wall corners.

qs = wind stagnation pressure for a minimum basic 50-year wind speed at a height of 30ft above

ground, as given for different regions of the United States in a wind speed contour map.

I = Importance factor taken as 1.15 for post-disaster buildings and 1.00 for all other buildings.

Calculation of qs

= Density of air = 0.0765pcf

Although at higher altitudes the value of air density should be reduced but UBC does not

consider its effect in calculations.

v = velocity of wind = 100mph

The formula becomes

7/31/2019 Wind load analysis By UBC for Tall buildings - Tall Buildings

2/3

Assignment No. 1: Wind Load Analysis by UBC Tall Buildings

h/w = 490/80 = 6.1 > 5 and h= 490ft > 400ft

UBC directs the users to adopt the standards like ASCE 7-02 for the design of such types of

structures.

Calculating the Ce factor

Ce = Kz x Gh

Ce = Gust factor coefficient

Kz = Velocity exposure coefficient

Gh = Gust response factor.

Exposure C: Scattered obstructions but also includes shoreline in hurricane prone region

The values of Ce is usually calculated from the following table but my height is greater than

400ft so its not included in the below table.

The chart did not provided values beyond 400 m so I approximated the values in calculations.

7/31/2019 Wind load analysis By UBC for Tall buildings - Tall Buildings

3/3

Assignment No. 1: Wind Load Analysis by UBC Tall Buildings

Pressure coefficient Cq

Walls

Cq for windward wall = 0.8 inwards

Cq

for Leeward wall = 0.5 outwards

Roof

Flat roof = 0.7 outwards

Importance Factor Iw

Iw = 1