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Re: ST - Allowable stresses for steel tees

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Richard Lewis responded :

>>What is the allowable bending stress per AISC-ASD for a steel tee (WT) with

>>the web in compression?  It does not appear to be covered by the

>>in Chapter F of AISC for allowable flexural stresses.   

>It is covered by Appendix 'B' in the 9th edition.


>Richard Lewis, P.E.
>Missionary TECH Team

Mr. Lewis,

I have contacted AISC regarding this matter and they say that the ASD 9th
does not address the allowable bending stress of WT sections with the stem in
compression.  App. B only address's WT sections that have non-compact webs.
 You cannot apply chapter F criteria to WT's with the webs in compression
since the buckling mode is completely different than what is assumed for
Chapter F.

The LRFD code does directly address this situation and AISC said that WT
should be designed to that criteria.  They also suggested for ASD design to
divide the LRFD ultimate moment strength by a "factor" to obtain an
approptiate allowable stress.

Respectfully Yours,