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Re: AISC LRFD- composite beams

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Be careful that you are comparing apples and apples.  The values that you quoted
for A36 steel are for full composite action.  That is a lot of weld studs.
Economical designs usually are based on partial composite action to reduce the
amount of weld studs.  The 30% number is a reasonable approximation of values
that have a wide variation,  some examples will be higher and some will be
lower, but the savings are real, if the deflection limit state doesn't govern.

Rick Drake, SE
Fluor Daniel, Aliso Viejo, CA


marfra(--nospam--at) on 01/18/2000 06:16:24 PM

Please respond to seaint(--nospam--at)

To:   seaint(--nospam--at)
cc:    (bcc: Rick Drake/AV/FD/FluorCorp)

Subject:  AISC LRFD- composite beams

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%.
The design charts and calcs indicate a considerably higher saving
particularly when beams under 16" are used with slabs 5" and over.This
is quite common for most buildings under 4 stories high. Deflections
usually are also fine.
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

Mark Francois