Simplified Frame Analysis - Simplified Design of Reinforced Concrete Buildings - page 25

2.2.2.1 Example: Calculation of Wind Loads - Building #2

For illustration of the ASCE procedure, wind load calculations for the main wind-force resisting system of
building #2 (5-story flat plate) are summarized below.

Wind-force resisting system:

Alternate (1) - Slab and column framing with spandrel beams
Alternate (2) - Structural walls

(1) Wind load data

Assuming the building is classified as closed (ASCE 6.5.9) and located in Midwest in flat open terrain.

Basic wind speed V = 90 mph ASCE Figure 6-1

Occupancy category II ASCE Table 1-1

Exposure category C ASCE 6.5.6.3

Wind directionality factor K d = 0.85 ASCE Table 6-4

Importance factor I = 1 ASCE Table 6-1

Topographic factor K zt = 1 ASCE 6.5.7

Gust effect factor G = 0.85 ASCE 6.5.8

External pressure coefficient C p ASCE Figure 6-6

Windward - both directions C p = 0.8

Leeward - E-W direction (L/B = 120/60 = 2) C p = -0.3

N-S direction (L/B = 60/120 = 0.5) C p = -0.5

Velocity pressure exposure coefficients K z (ASCE 6.5.6.6) at various story heights are summarized in Table 2-1

Velocity pressure q z = 0.00256K z K zt K d V 2 I ASCE 6.5.10

Design wind pressure p z = q z GC p ASCE 6.5.12.2

(2) Design wind pressure in the N-S Direction

Table 2-2 contains a summary of the design pressures calculations for wind in N-S direction.

Table 2-2 Design Pressures for N-S Direction

Height
above
ground
level, z
(ft)

Windward
design
pressure
q z GC p
(psf)

Leeward
design
pressure
q h GC p
(psf)

Total
design
pressure
(psf)

Level K z q z

(psf)

Roof 63 1.148 20.2 13.8 -8.6 22.4

4 51 1.098 19.4 13.2 -8.6 21.8

3 39 1.038 18.3 12.4 -8.6 21.0

2 27 0.961 16.9 11.5 -8.6 20.1

1 15 0.849 15.0 10.2 -8.6 18.8