Design Considerations for Earthquake Forces - Simplified Design of Reinforced Concrete Buildings - page 298

Total wall weight = 3.53(63) = 222 kips

Roof dead load = 0.122(480) = 59 kips

Four floors dead load = 0.142(480)(4) = 273 kips

Total dead load = 222 + 59 + 273 = 554 kips

Proportion total dead load between wall segments:

Two 8 ft segments: (2 96 in.) = 192/440 = 0.44

One 20 ft-8 in. segment: (248 in.) = 248/440 = 0.56
For two 8 ft segments: Dead load = 0.44(554) = 244 kips
One 20 ft-8 in. segment = 0.56(554) = 310 kips
Roof live load = 20(480)/1000 = 10 kips
Four floors live load = (29.5 + 24.5 + 22.5 + 21) (480)/1000 = 47 kips (see Section 5.7.1)

Proportion of live load between wall segments:

Roof live load
For two 8 ft segments = 0.44(10) = 4.4 kips

One 20 ft-8 in. segment = 0.56(10) = 5.6 kips

4 floors live load
For 2-8 ft segments: = 0.44(47) = 21 kips

1-20 ft-8 in. segment = 0.56(47) = 26 kips

Recall wind load analysis (see Chapter 2, Section 2.2.1.1):

For wind load N-S direction

M = [(16.2 63) + (31.6 51) + (30.6 39) + (29.2 27) + (30.7 15)]/2 = 2537 ft-kip

The axial force, bending moment, and shear acting on the base of the 20'-8” long shear wall resisting lateral loads
in the N-S direction are summarized in Table 11-5. Table 11-6 shows the factored axial force, bending moment and
shear. It is clear from the table that seismic forces will govern the design of the shearwalls in this example.

Story Drift and P- Effect

To check that the maximum allowable limits for story drift are not exceeded (ASCE Table 12-12.1) the
displacement at each floor level δ xe need to be calculated and amplified (See Section 11.8). Then the stability

index θ should be calculated and checked against 0.1 where the P- effects are not required to be considered.