sm7 85

________________________________________________________________________
PROBLEM (7.85) Design a cantilever beam of uniform strength having a rectangular cross
section with constant depth h and varrying width b, supporting a concentrated load P at its free
end as shown in Fig. P7.85.
Assumption: Only the normal stresses due to the bending need be considered; the permissible
stress is all
σ
.
SOLUTION
2
2
6
;
6all
bh M Px
MPx S Sbh
σ == ==
or
2
6
all
Px
bh
σ
=
Let width at fixed end (x = L):
2
6
oall
PL
bh
σ
=
Then
o
bx
bL
= or o
x
bb
L
=
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