________________________________________________________________________
PROBLEM (7.28) As depicted in Fig. P7.28, two vertical concentrated forces are applied to an
S380 x 64 steel beam (see Table B.9) resting on the ground. Determine the largest bending stress in
the beam.
SOLUTION
1.6 m
120 kN
120 kN
B
wr
0.4 m
A
D
C 0.4 m
Sz=977x10-6 m3
y
z
S 380x64
C
Moment at C and D:
32
1(100 10 )(0.4)
2
CD
MM== × 8kN m
=
⋅
At midspan: 32 3
max 1(100 10 )(1.2) 120 10 (0.8) 24
2
M
kN m=× −× =−⋅
Thus, 3
max
max 6
24 10 24.6
977 10
z
M
M
Pa
S
σ
−
×
== =
×
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