________________________________________________________________________
PROBLEM (7.68) A cantilever beam, having a built-up cross section is loaded as shown in Fig.
P7.68. Determine:
(a) The maximum bending stress in the beam.
(b) The maximum shearing stress in the beam
Given: P = 800 N, M = 200 N⋅m
SOLUTION
y
z
240 m
m
200 N
⋅
m
44
240 160
12
I−
=
46
1087.221 mm×=
(a) 3
max 6
1000(120 10 ) 541
221.87 10
Mc kPa
I
σ
−
−
×
== =
×
(b)
max 120 240 60 80 160 40Q=××−××
34
1216 10 mm=×
6
max
max 63
800(1216 10 )
221.87 10 (80 10 )
VQ
Ib
τ
−
−−
×
== ××54.1 kPa
=
V, N
x
x
M
, kN⋅m
800 N
1000 N m ⋅
-800
0.5 m 1 m
800 160 mm
800
-1000
-600
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