Civil Engineering Reference
In-Depth Information
Figure G5-9
Partial load cases
for roof purlins in
Example 5-2.
Solution
As before,
C
e
is 1.0,
I
s
is 1.2, and
p
g
is 20 lb/ft
2
, but now
C
t
is 1.0 and the
roof slope factor from Figure 7-2(a) is as follows:
.
oo
14
−
5
C
s
=
10
086
.
−
=
o
65
The fl at roof snow load becomes
16.8 lb/ft
2
p
f
=
0.7
C
e
C
t
I
s
p
g
=
0.7(1.0)(1.0)(1.2)(20)
=
(round to 17 lb/ft
2
)
The balanced snow load is
0.86 (17 lb/ft
2
)
14.6 lb/ft
2
(round to 15 lb/ft
2
)
p
s
=
C
s
p
f
=
=
For 5 ft purlin spacing, the full- and half-balanced loads are
balanced
=
15 lb/ft
2
×
5.0 ft
=
75 lb/ft
half-balanced = ½(75 lb/ft) = 37.5 lb/ft (round to 38 lb/ft)
