huangyhg

one-way pt on steel beams?
hi fellow structural engineers,
i've had an architect propose that we have steel beams support our 34' one-way pt slab. it's got me a little concerned. we have had an old-school se consulatant claim that this is fine with an l/600 non-composite design criteria.... and he proposes add studs at 12" anyway. which seems like a bit of self-deception: that there should be a real design composite criteria if you are going to put in studs.
i'm wondering if we'll be having conflicts, shrinkage, cracking, vibration, long-term creep etc, etc?
is there any real design criteria for this, rather than a (unverified) "rule of thumb?" i have trouble believing off-the-hip "rules of thumb" will stand up in a court room. not unless someone really verifies that it is the standard of care in the local engineering community.
thanks for your help!
mike in seattle

what is the problem or concern that you are questioning? l/600 seems like high quality construction for live load deflection after completion. i would suggest shored concrete forms so plastic concrete does not deform the beam prior to gaining concrete strength and post tension compression.
hi civilperson,
thank you for your quick reply.
well, so i imagined the pt slab would be on flat forms, but wouldn't that make the situation worse by having both a live load transfer and a dead load transfer once the forms are pulled?
as for l/600, aside from a m/s < fcr.stress -> 6.7*root_f'c, what is the tolerance of concrete for deflection?
thank you!
mike

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