Assignment No. 3 : Wind Pressures (NBCC) (30-Story Building in Toronto) Assignment 3: Calculations for Wind Pressures (NBCC) (30-Story Building in Tor...
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Assignment No. 3 : Wind Pressures Pressures (NBCC) (30-Story Building in Toronto)
Assignment 3: Calculations for Wind Pressures (NBCC) (30-Story Building in Toronto) Given Data My Serial No = 33 Nature of Building: Typical Office Building Stories: 30 + 33 = 63 Stories First floor height: 17ft Typical storey height: 13 ft Building height, h: 17 + (62x13) = 823 ft. Location: Toronto, Ontario Wind speed V: 110 mph Terrain: Flat, open country with scattered obstructions obstructions having the size of single -family
dwellings, height generally less than 30 ft Plan dimensions: Width ‘W’ (along wind) = 98.5 ft (B); Depth ‘D’ (cross wind) = 164 ft; Building
height, H: 823 ft. Width ‘W’ (along wind) = 98.5 ft (B) = 30.02 m Depth ‘D’ (cross wind) = 164 ft = 49.98 m
Building lateral-load-resisting system: moment frame with shear walls. Fundamental period T= 3.12 sec. Damping co-efficient: 1.5% of critical; Building density = 195 kg/m
Required: 1. Determine the wind pressure on the windward and leeward sides as well as total wind pressure on the building. 2. Total load/ft at each floor level and the Total base shear. 3. Overturning moment (OTM) at each floor level and total OTM. 4. Calculate maximum along and across-wind accelerations. Comment whether the building is safe and comfortable to occupants under dynamic wind gust effect. NBCC- wind analysis The external pressure or suction on the building surface is given by the equation:
Afzal Waseem
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Assignment No. 3 : Wind Pressures Pressures (NBCC) (30-Story Building in Toronto)
If the wind speed NBCC - wind analysis V is in m/s, the design pressure ‘q’ in kPa, is obtained by using a value of C = 650 x l0 -6. Wind speed V: 110 mph
1 mile = 1 609.344 meters 1 mph = 0.44704 meters / second V = 110 mph = 49.1744m/s -6
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q = 650 x 10 x (49.1744m/s) = 1.572 kPa
Detailed Procedure: H= 823 ft = 250.85 m 1 foot = 0.3048 meters 1 mile = 1 609.344 meters 1 mph = 0.44704 meters / second V = 110 mph = 49.1744m/s
Exposure Factor Ce: Based on the mean wind speed profile, depending on the roughness of terrain before wind reach the building. Our Terrain: Flat, open country with scattered obstructions having having the size of single-family dwellings, height generally less than 30 ft
It best fits in Exposure A Exposure A: The exposure is defined as open, level terrain with only scattered buildings, trees or other obstructions and open water or shorelines. Ce for a given height (z) is given by:
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Assignment No. 3 : Wind Pressures Pressures (NBCC) (30-Story Building in Toronto)
This will vary with the height of the building, where z will be the height of the floor.
Gust Effect Factor (Dynamic Response Factor) Cg: The dynamic gust response factor is defined as the ratio of peak loading to mean loading
H =250.85m CeH = 2.8 Afzal Waseem
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Assignment No. 3 : Wind Pressures Pressures (NBCC) (30-Story Building in Toronto)
W/H = 164/823 = 0.1993 Height of the structure was H =250.85m so I took the value B = 0.5 W =164 ft
no = 1/T = 1/3.12 = 0.321 Hz VH = mean wind speed = 49.1744m/s
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Assignment No. 3 : Wind Pressures Pressures (NBCC) (30-Story Building in Toronto)
S = 0.05
no = 1/T = 1/3.12 = 0.321 Hz VH = mean wind speed = 49.1744m/s
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Assignment No. 3 : Wind Pressures Pressures (NBCC) (30-Story Building in Toronto)
F =0.25
Damping co-efficient: 1.5% of critical = 0.015 Putting all the above calculated values in the following formula
K = 0.08 CeH = 2.8 W =164 ft S = 0.05 F =0.25 = 0.015
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Assignment No. 3 : Wind Pressures Pressures (NBCC) (30-Story Building in Toronto)
V=
= 0.2537 gp = 3.8
The Required Ghust Factor Cg = 1.7418 Complete calculations are attacked in the table.
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Assignment No. 3 : Wind Pressures Pressures (NBCC) (30-Story Building in Toronto) 1.
Calculate maximum along and across-wind accelerations. accelerations.
Based on wind tunnel studies, NBCC gives two expressions for determining the across (aw) and along (a D) wind accelerations:
= H/450 = 250.85/450 = 0.557
no = 1/T = 1/3.12 = 0.321 Hz = nW = nD Width ‘W’ (along wind) = 98.5 ft (B) = 30.02 m Depth ‘D’ (cross wind) = 164 ft = 49.98 m