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Re: AISC LRFD- composite beams

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Marc,

> I find it strange that most texts including the Salmon & Johnson advise
> that using steel beams composite with concrete slabs generate savings of
> 20% to 30%.
>....
> A typical W10X15 has an permissible Mn of 43 kip ft . When composite
> with a 5" slab the permissible is generally over 75 kip ft. Im I doing
> something wrong

In addition to floor vibrations, did you check strength and deflections
during construction ?

The composite capacity is not developed until the concrete hardens.
When the concrete is placed, the steel section must resist the dead
weight of the concrete (plus any other applied loads).  Metal decking
or formwork might, or might not, be able to provide bracing against
lateral buckling of the compression flange.


Ed.S.
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Edwin R. Schmeckpeper, P.E., Ph.D.
Department of Civil Engineering                   Phone  : (208) 885-6702 
University of Idaho                               FAX    : (208) 885-6608
Moscow, Idaho 83844-1022                          E-Mail : eds(--nospam--at)uidaho.edu
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