huangyhg

allowable beam rotation
can anyone provide some guidance on allowable rotations of w-sections for servicability considerations?
i have an architecturally finished wall section being supported by the w-sections. however, the wall is two feet off the centerline of the beam, and is creating a substantial torsional moment. the wall finish is sensitive to deformation and the beams cannot be laterally braced.
any guidance on this issue would be greatly appreciated.
need more information. is the wall parallel to the beams, what is it supported by? why is the beam in torsion, is there a cantilever?
perhaps more description might help us!
the wall is running parallel to the beam. the wall is supported by a canilever system attached to the top flange of the w-section. the distance between the centerline of the beam and the center of mass of the wall/wall support system is two feet.
what type of wall? what type of deck? weight of the wall on the cantilever? if you can't kick back to the deck or another beam can you add framing to kick back to?
the structure is a large four story atrium-like entrance, but with minimal windows. there is no decking, ect. to tie it back to and no additional framing can be added. the cantilever-wall system is to be cold form shapes with an architectural finish on the cold-form wall frame. the finish weighs 18 psf on beam spacings of ten feet. beam spans are twenty feet and column/wall placements cannot be altered due to the retrofit nature of the project.
do you have to use a wf? i would try to use an hss.
i would either use an hss or reinforce the wf with side plates to make a closed section (tube).
i agree that a tube would be a better solution here.
but, back to your original question--the serviceability issue is with items attached to the beam, and not the beam itself. for example, what does the beam rotation do to the wall system? a small rotation in the beam could result in a large deflection in the wall system. the wall system will rotate with the beam, where it is attached to the beam.
daveatkins
right. i was informed that the wall finish would be very rigid, but could crack due to any substantial deformations.
i have taken care of local deflections on the wall.
i was worried about the beam rotations because any differential in rotation from beam to beam could cause deformations. i had hoped to counteract this by limiting beam sizes, but i am limited with how large a beam i can use.
i actually meant to write limiting beam rotations, not limiting beam sizes.

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