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PROBLEM (10.37) A cantilever of variable cross section supports a uniformly distributed load w
(Fig. P10.37). Verify, using the last of Eqs. (10.4), that the expression for the deflection curve is
v=
wL
(− x 3 + 3L2 x − 2 L3 )
Eb0 h3
(P10.37)
Here h represents the depth of the beam and b0 is the width at the fixed end.
SOLUTION
1 x
( b0 )h3
12 L
The last of Eq. (10.4):
(b0 x L)h3 d 2 v
d2
d 2v
d2
(
)
[
] = −W
EI
=
E
dx 2
dx 2
dx 2
12
dx 2
Integrating twice
(b x L)h3 d 2 v
d
[E 0
] = − wx + C1 = −V
dx
12
dx 2
I=
(b0 x L)h3 d 2 v
1
E
= − wx 2 + C1 x + C2 = M
2
12
2
dx
Boundary conditions:
M (0) = 0 : C2 = 0
V (0) = 0 : C1 = 0
Equation (1) becomes then
d 2v
6wL
dv
3wL 2
=−
x
=−
x + C3
2
3
dx
Eb0 h
dx
Eb0 h3
wL 3
v=−
x + C3 x + C4
Eb0 h3
We have
3wL3
2 wL4
v '( L) = 0 : C3 =
,
v ( L ) = 0 : C4 = −
Eb0 h3
Eb0 h3
Substitution of these into Eq (2) results in Eq. (P10.37).
(1)
(2)
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