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Steel diaph. and 1/3 increase

Steel diaph. and 1/3 increase

Steel diaph. and 1/3 increase

Vulcraft's 2001 steel deck diaphragm tables (p.67) notes that a 1/3 increase has already been taken for short term loads and the values should not be increased again. Since ASCE7 does not recognize a 1/3 increase for dead and wind only, shouldn't the values in the diaphragm tables therefore be multiplied by 0.75 to account for this? Is everyone else doing this?

RE: Steel diaph. and 1/3 increase

ASCE 7 never deals with the 1/3 stress increase as it only deals with loads....not design.

IBC 2000 has monkeyed with the 1/3 stress increase to limit its use for load combinations that have two or more transient loads included in the combo.  

So I would agree that the 0.75 factor should be used (under the IBC) for load combinations such as 0.6D + W or 0.6D + 0.7E but not for load combos such as D + W + L + Lr.

I'm not sure where it is, but there was a good thread discussing the 1/3 issue relative to the IBC.

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