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WTCA/ASCE Floor Deflection criteria

WTCA/ASCE Floor Deflection criteria

WTCA/ASCE Floor Deflection criteria

(OP)
Need to locate some info

I'm a designer working at a truss plant and one of the Sales guys is questioning why we increase our defection setting from 360/240 to 480/360 for our floor trusses when light weight concrete is added to the floor system.

I explained the whole "brittle floor" concept to him and our PE requires this increase on deflection to keep the concrete from cracking over time.

Wondering if anyone knows where to find the actual guideline laid out for this situation. The sales people did not figure the increase in cost into his bid. If i had an actual guideline i could pass to the sales people they would have no excuse for not figuring their bid correctly.

RE: WTCA/ASCE Floor Deflection criteria

Check with your truss plate supplier.

Masonry has often used l/500 or l/600.

Also - I have seen this happen on steel deck/concrete floors where they did not shore the midspan of the steel deck.  They started pouring concrete and unbeknownst to the workers the steel deck deflected and they added MORE concrete.  The steel deflected more - more concrete.  You can see where that went......

RE: WTCA/ASCE Floor Deflection criteria

Kobi,

If you look at the manufacturers specs for the crete they usually have deflection limitations.

For instance, maxxon has a delfection limitation of L/360 in their "drying conditions sheet" for gypcrete.

RE: WTCA/ASCE Floor Deflection criteria

I believe the IBC requires L/600 when supporting concrete/masonry

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