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Re: Garage Floor in Residential House

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I did some quick calculations and the deflection under the given loading +50
pounds for member weight is 49.69" .   The transformed  moment of inert. for
the given section is 882 in^4 and reduces the deflection to 2.36" so you
might consider having it retrofitted with shear studs - it would also brace
the flange.

                                                                Greg
-----Original Message-----
From: Horning, Dick/CVO <dhorning(--nospam--at)CH2M.com>
To: 'seaint(--nospam--at)seaint.org' <seaint(--nospam--at)seaint.org>
Date: Friday, February 05, 1999 3:15 PM
Subject: RE: Garage Floor in Residential House


>My $.02 - I wouldn't rely on it.  You need to prevent twisting of the
>compression flange about a longitudinal axis.  If the secondary members
were
>of steel and attached to the upper 1/3 of the web of the girder, AISC would
>consider it braced, but with wood I would be concerned about crushing of
the
>2x12s before they could develop enough restraint.
>
> -----Original Message-----
> From: Rob Quiring [SMTP: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
>
>