Page 385 - Design of Reinforced Masonry Structures

6.36 CHAPTER SIX

2
Wall forces—Interior Zone 5 for effective area of 10 ft (Table 6.3):
⎧ ⎪ 14 .6 lb/ft (inward pressure) ⎫ ⎪
2
p = ⎨ ⎬
net30 − 2
⎩ ⎪ 19 .5 lb/ft (outward pressure) ⎭ ⎪
w
Design wind pressure:
⎧ ⎪ 115 146) = 168 lb/ft 2 (inward pressure) ⎫ ⎪
.
.
.
(
w = p = 1.15p net30 = ⎨ ⎬
net
⎩ ⎪ 115(−119 5.) =− 22 4 lb/ft 2 (outward pressure )⎪
.
⎭ ⎭
.
b. Calculate seismic load: Lateral seismic load on the wall would be calculated sepa-
rately for the wall (w ) and for the parapet (w ).
u1
u2
w = 0.4S IW p
DS
u1
Determine short-period spectral acceleration parameter S :
DS
S = 150%g = 1.5g
S
S = 90%g = 0.90g
1
2
S = / 3 S
DS MS
S = F S
a S
MS
Site class is unknown; assume Site Class D.
For Site Class D and S ≥ 1.25g,
S
F = 1.0 (ASCE 7-05 Table 11.4-1)
a
Therefore, S = F S = (1.0) (1.5g) = 1.5g
a S
MS

2
2
S = / 3 S = / 3 (1.5g) = 1.0g
MS
DS
Determine 1-s period spectral acceleration parameter S :
D1
For Site Class D and S ≥ 0.25g,
1
F = 1.5
v
Therefore, S = F S = (1.5) (0.9g) = 1.35g
M1 v 1
2

2
S = / 3 S = / 3 (1.35g) = 0.90g
M1

D1
For Occupancy Category III,
I = 1.25 (Table 6.4)
Determine the seismic design category: From ASCE 7-05 Table 11.6-1, for Occupancy
Category III having S ≥ 0.50g, SDC is D. From ASCE 7-05 Table 11.6-2, for Occupancy
DS
Category III having S ≥ 0.20g, SDC is D. Therefore, SDC for the building is D.
D1
2
The dead weight of the wall @ 84 lb/ft ,
W = (84)(22.67) = 1904 lb
p
W = 0.4S IW = 0.4(1.25)(1904) = 952 lb (acting at the center of gravity)
p
u1
DS