Steel Transfer Beam supporting Wood Bearing Walls above
Steel Transfer Beam supporting Wood Bearing Walls above
(OP)
I have some 30ft long span steel beams transferring out 3 stories of wood bearing walls above. Using, L/360 or L/480 i'm limited to 1" or 0.75" total deflection respectively. I'm leaning towards limiting the deflection to a tighter limit like 1/2", since it is supporting gypsum sheathed wood walls above - but the beam sizes are becoming rather large. What deflection criteria would you use?






RE: Steel Transfer Beam supporting Wood Bearing Walls above
DaveAtkins
RE: Steel Transfer Beam supporting Wood Bearing Walls above
And, you could camber the stl. beams for most of the DL. Then, know too, that the framed and sheathed walls will act like deep beams to some extent, depending upon number and location of wall openings; and that it is unlikely that you will ever get full LL, from three stories on those stl. beams at the same time. While you may not want to (or be allowed to by code) apply a LL reduction on the stl. beams for their design, it may give you some confidence that the deflections will not be excessive.
RE: Steel Transfer Beam supporting Wood Bearing Walls above
RE: Steel Transfer Beam supporting Wood Bearing Walls above
Take full advantage of live load reduction allowed by code, which will likely reduce floor live load substantially (up to 50-percent), depending on total floor area being supported by beam.
John F Mann, PE
www.structural101.com
RE: Steel Transfer Beam supporting Wood Bearing Walls above
RE: Steel Transfer Beam supporting Wood Bearing Walls above
However, as it's steel there will be no creep. Therefore you will see full dead load deflection by the job's end, so it's only LL deflection which will contribute to visible cracking. Any cracking due to DL will be repaired before completion.
For extra peace of mind you could specify the drywall immediately above the beam to be fixed last.
RE: Steel Transfer Beam supporting Wood Bearing Walls above
"For drywall assemblies it is desirable to limit deflection to L/240 (L = length of the span) and to never exceed L/120 (L/180 in some codes). The preferred limit for veneer assemblies is L/360 and should not exceed L/240."
See the second page of this USG publication:
http://www.usg.com/content/dam/USG_Marketing_Commu...
www.SlideRuleEra.net
www.VacuumTubeEra.net
RE: Steel Transfer Beam supporting Wood Bearing Walls above
There is a good bet the architect won't call that out.
When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.
-R. Buckminster Fuller