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American Steel Design
Section 2
2-88
1.
Global Bending:
Global bending check is done at the web post section. This is the
region of the member where the full cross section is active,
without interference of the holes.
The actual bending stress is computed at the middle of the web
post location and is obtained by dividing the moment by the
section modulus of the full section.
For computing the allowable bending stress, the compactness of
the section is first determined in accordance with Table B5.1 in the
Chapter B of the AISC 9
th
edition specifications. The rules
applicable to I-shaped sections are used for this. Following this,
the allowable bending stress is computed per chapter F of the
same.
The ratio is computed by dividing the actual stress by the
allowable stress.
2. Vierendeel Bending:
This is checked at the middle of the hole locations. The effective
cross section at these locations is a Tee. The overall moment (Mz)
at the span point corresponding to the middle of the hole is
converted to an axial force and a moment on the Tee.
The actual stress is computed at the top and bottom of each Tee
section.
fa = M / ( deffect * At )
where At is the area of the Tee section
fb = V * e * a / ( 2 S )
where a is the area factor. For the top Tee section, a = Area of Top Tee / (
Area of Top Tee + Area of Bottom Tee )