Civil Engineering Reference
In-Depth Information
SOLUTION
Assume Beam
wt
400 lb/ft
w
u
(1.2)(2
0.400)
(1.6)(3)
7.68 k/ft
M
u
(7.68)(25)
2
8
600 ft- k
(0.18)(3)
60
0.009
M
u
bd
2
482.6 from Appendix Table A.12
482.6
(12)(600,000)
M
u
bd
2
(0.9)(482.6)
Solving this expression for
bd
2
and trying varying values of
b
and
d
.
b
d
16
32.19
18
30.35
20
28.79
16,577
k
seems reasonable
Try 18
33 Beam (
d
30.50 in.)
Bm wt
(18)(33)
144
(150)
619 lb/ft
the estimated 400 lb/ft
N.G.
Assume Beam wt a Little Higher than 619 lb/ft
Estimate wt
650 lbs/ft
w
u
(1.2)(2
0.650)
(1.6)(3)
7.98 k/ft
M
u
(7.98)(25)
2
8
623.4 ft- k
M
u
482.6
(12)(623,400)
bd
2
(0.9)(482.6)
16
32.81
18
30.93
20
29.35
17,223
Try 18
34 Beam (
d
31.00 in.)
(18)(34)
144
Bm wt
(150)
637.5 lbs/ft
650 lbs/ft
OK
4.4
MISCELLANEOUS BEAM CONSIDERATIONS
This section introduces two general limitations relating to beam design: lateral bracing
and deep beams.
