Page 381 - Design of Reinforced Masonry Structures

6.32 CHAPTER SIX

on or attached to the structure requires design conforming to the provisions of ASCE 7-05
Chap. 13, with the following exceptions in five categories:
1. Architectural components in Seismic Design Category B, other than the parapets sup-
ported by bearing walls or shear walls provided that the component importance factor,
I (discussed later), is equal to 1.0.
p
2. All mechanical and electrical equipment in Seismic Design Category B.
3. Mechanical and electrical equipment in Seismic Design Category C are exempt, pro-
vided that I = 1.0.
p
4. Mechanical and electrical equipment in Seismic Design Categories C, D, E, and F are
exempt if I = 1.0, and either
p
(a) Flexible connections between the components and ductwork, piping and conduit are
provided.
(b) Components are mounted at 4 ft (1.22 m) or less above a floor level and weigh 400 lb
(1780 N) or less.
5. Mechanical and electrical equipment in Seismic Design Categories D, E, and F are
exempt if I = 1.0, and
p
(a) Flexible connections between the components and ductwork, piping and conduit are
provided.
(b) The components weigh 20 lb (89 N) or less, for distribution systems, weighing
5 lb/ft (73 N/m) or less.
The value of the component importance factor (I ) alluded to in the preceding paragraph
p
is either 1.0 or 1.5 depending on whether the structure to which it is attached has life-safety
importance or hazard-safety importance. The value of I is assumed to be 1.5 when the
p
following conditions apply:
1. The component is required to function for life-safety purposes after an earthquake,
including fire-protection sprinkler systems.
2. The component contains hazardous materials.
3. The component is in or attached to Occupancy Category IV structure, and it is needed
for the continued operation of the facility, or its failure would impair the continued
operation of the facility.
The horizontal seismic force normal to the component, F , is given by Eq. (6.7):
p
.
04 aS ⎛ z ⎞
+
F = p DS ⎜ 12 ⎟ W (6.7)
⎛ ⎜ R p ⎞ ⎝ h ⎠
p p
⎟
⎝ I ⎠
p
The value of F given by Eq. (6.7) is not required to be greater than
p
F = 1.6S I W (6.8)
p DS p p
or less than F given by Eq. (6.9):
p
F = 0.3S I W (6.9)
DS p
p
p
where F = seismic design force to be applied normal to the component at its center of
p
gravity, and distributed over its height relative to the mass distribution of the
component.