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American Steel Design
Section 2
2-30
manual) and Composite beams (I shapes with concrete slab on top)
is not suppported.
Allowable Stresses per AASHTO Code
The member design and code checking in STAAD is based upon
the allowable stress design method. It is a method for
proportioning structural members using design loads and forces,
allowable stresses, and design limitations for the appropriate
material under service conditions. It is beyond the scope of this
manual to describe every aspect of structural steel design per
AASHTO specifications because of practical reasons. This section
will discuss the salient features of the allowable stresses specified
by the AASHTO code. Table 10.32.1A of the AASHTO code
specifies the allowable stresses.
Axial Stress
Allowable tension stress, as calculated in AASHTO is based on the
net section. This tends to produce a slightly conservative result.
Allowable tension stress on the net section is given by,
FF
ty
=
055.
Allowable compressive stress on the gross section of axially
loaded compression members is calculated based on the following
formula:
F
F
E
when Kl r C
a
y
c
=<
F
F.S.
(1- (Kl / r)
y
2
4
2
π
(/)
F
E
F S Kl r
when Kl r C
ac
=>
π
2
2
..( /)
(/)
with E F and F S
y
C (2
c
2
==π /) ...
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