sm12 56

________________________________________________________________________
PROBLEM (12.56) For the truss loaded as shown in Fig. P12.56, determine the horizontal de-
flection at point C. Use Castigliano's theorem.
SOLUTION
Apply the method of joint at
C & B:
P
55
68
BC
FQ=− − P
55
68
AC
FQ=−P
13
28
BC
FQ=+P
We have
15
26
AC BC
AB FF
F
QQQ
∂∂
∂==
∂∂ ∂
5
6
=−
Let Q=0:
1i
Hi
F
FL
AE Q
δ
∂
=∂
∑i
13 5 55 5 5 5
[()()(
82 8 66 8 6 6
PL PL PL
AE )]−+−−=+
3
16 PL AE
=→
A
2
P
B
5L/6
5L/6
CQ
L/3 2
L
P
2
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