________________________________________________________________________
PROBLEM (7.29) A W 410 x 60 wide-flange beam (see Table B.8) is reinforced by two 240 x 10
mm steel cover plates of the cross section shown in Fig. P7.29. The beam carries a uniformly distributed
load w on a simply supported span of 10 m. For an allowable bending stress of 120 MPa, calculate the
largest permissible value of w.
SOLUTION
2
max 1(10) 12.5
8
M
ww==
5w
A
B
w
( I )WF=216x10-6 m4
10 m 5w240 mm
WF410x60
y
407 mm
z
Plate
427 mm
C
The moment of inertia of cover plates about z:
33 64
240(427 407 ) 208.7 10
12
p
I
mm
−
==×
Thus 64
( ) 424.7 10
WF p
I
II −m=×=+
and
max all
M
Ic
σ
= gives:
66
3
120 10 (424.7 10 )
12.5
213.5 10
all
w−
−
××
=×
Nm
or wk19.1
all ⋅
=
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