
179Appliances and Equipment Failures
e actual loads must be compared to the design loads in order to determine the
likelihood of failure. e interaction equation (I.E.) allows the conditions of failure to be
determined:
I.E. 1.0=+≤
−−
σ
σ
cen
allc
bend
allb
(6.34)
where
σ
all-c
is the allowable axial stress (ksi)
σ
all-b
is the allowable bending stress (ksi)
e value calculated for I.E. must be less than or equal to 1.0 for the member to be ade-
quate. If the I.E. value is above 1.0, then the member will fail.
e allowable stresses are based on safety factors determined by the American Institute
of Steel Construction (AISC):
σ
σ
allc
CR
allb y
FS
_
_
..
=
=σ 0.66 ...