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Re: 2x Built-up columns.

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> Hi,
>
> Moving from southern California to St. Louis, MO,  I noticed more built-up
beams and columns in the residential construction here. 2-2x4 or 3-2x4 as
columns to support girder trusses with up to 8000 lbs. or 12000 lbs, If the
column ht goes to more than 12',  I saw some 2x6 s. 10d or 16d nail @ 12" or
24" are common for these built-up columns. ½" plywood exterior and ½" gyp
board interior are the only bracing for those columns. Per NDS 97 sec. 15.3,
I have problems to justify the design. But I have been told, they built
thousands of houses like these, none of these columns failed. Please help me
!
>
>
> Helen Zhou  PE
>

Are these columns in an open space, or columns within a wall?

IMO, if they're within a wall they can be treated as multiple studs,
restrained by the wall sheathing.

But beware of bearing stress across the grain at the top and bottom plates -
I've noticed some truss manufacturers give required bearing areas based on
the allowable stresses of the girder truss material, which might be higher
than allowed for the plate material. Also, the capacity of a "stocky" stud
(parallel to grain) often exceeds the capacity of the plates across the
grain.

Peter James



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