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RE: Garage Floor in Residential House

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Sorry, I misunderstood the problem. I thought that the nailer was applied at the top and bottom flanges and that the lack of a tight plywood connection was due to the nail length of the nailer. I reread the email and I was way off base.
Now as I understand, the steel is 13.84" in depth less the flange (0.384"), the nailer 1-1/2", the 2x12 is 11.25" which gives a net difference betwee the top flange of the beam and the 2x12's of .705". If the plywood is nailed to the top of the 2x12's, the the net difference is .205 (assuming the plywood does not extend over the steel).
 
The calculated dead load deflection at mid span will be around 1/4" (based upon the 60psf dead load applied.
 
In order to get the 1/2" space betwen the plwd and the joists, I would assume that you extended the plywood over the steel. Is this correct?
 
I'll check some of the other responses to see if anyone got this one clearer than I did. Compression flange bracing for this member should be at least at the center of the beam so as not to exceed 12' unbraced length.
 
I would assume that even if the flange were to buckle in compression, the joists would prevent the deflection out-of-plane of the beam - therefore providing at least some lateral support. If this is the general consciences, the the beam would be considered braced at closer than12' and I would not see a problem with flange buckeling.
 
Interesting problem
Dennis Wish PE
 
-----Original Message-----
From: Rob Quiring [mailto:robq(--nospam--at)uniserve.com]
Sent: Friday, February 05, 1999 12:12 PM
To: seaint(--nospam--at)seaint.org
Subject: Garage Floor in Residential House

I have a garage floor that is 21'x21' square, that supports cars and light trucks (50 psf live load + 60 psf dead load) and is constructed with 2x12 DFir @ 12" o.c. (span 10') flush framed into a steel W14x30 steel (simple support) beam that spans 21' from front to back at the middle of the garage.
 
a 2x4 is bolted on top of the bottom flange at 36" o.c. each side of the beam. the 2x12 are framed on top of the 2x4 with blocking every second space.
 
2x4 strapping run perpendicular at 16" o.c. on top of the 2x12 to allow for venting, with 5/8" plywood, waterproof membrane, and 4" of concrete on top.
 
my problem is that there is a 1/2" gap between the top of the steel top flange and the plywood floor above providing no lateral support for the beam at the top flange.
 
my Question is: do the 2x12's framed tight against the web of the beam, which stop 1/2" shy of the bottom of the top flange provide lateral support for the top flange of the beam when the beam is in compression?
____________________________________________________
Rob Quiring
Isaak Engineering
Abbotsford, BC