Question

Question 7: Wind Load A building is on an open flat terrain in Baltimore City. If what are the external wind pressure acting on the wi long. The roof of the building is essentially flat and fully enclosed. Parameter Value 105 miles/hr am in Baltimore City. If the side wall of the building is 20 ft high, sure acting on the windward and leeward walls? The wall is 60 ft V First Floor Slab K, -0.85 for wall height between 0-15 ft K-0.90 for wall height of 20 ft 0.85 Find Cp based on L/B

Answer 1

Ans) We know, velocity pressure coefficient (q),

q = 0.00256 K_z K_zl K_d V² I  

where, K_z = height factor = 0.90 for 20 ft wall  (given)

K_zl = topographical factor = 1 (given)

K_d = wind directional factor = 1 (given)

V = Wind velocity = 105 miles/hr

I = Importance factor = 1 for ordinary buildings

Putting values,

q = 0.00256 (0.90)(1)(1)(105)²

=> q = 25.4 psf

Now,

External wind pressure on windward wall, P_e = q G Cp

where, Cp is external wall pressure coefficient = 0.80 for windward wall

=> P_e = 25.4 x 0.85 x 0.80 = 17.27 psf

External wind pressure on leeward side , P'_e = q G Cp

To determine Cp for leeward wall , find L and B

L = Length of building = 60 ft

B = Width = 20 ft

For L / B = 60/20 = 3 and exposure B ,Cp = -0.50

=> P'e = 25.4 x 0.85 x (-0.5) = -10.8 psf