Lateral Torsional Buckling

[mann]

I have two W8x18 beams that are approx. 14.5' in length.  The beams are bearing in a brick wall at one end and are sitting on a 8"x8" bearing pad on a column at the other end.  The beams are 21' apart.  A 12x24 enclosure has been placed on the two beams.  The enclosure rests on two W10x26 I beams which in turn sit directly on top of the two W8 beams.  The back of the enclosure is 6' from the wall bearing and cantilevers about 3.5' beyond the end of the W8 beams.  (The W10 beams are 12' in length) The total weight of the enclosure is 24 kips.  The W10 beams were placed slightly off center of the W8 beams (about 1/8&quot and the two W8 beams were not completely level.  One of the column bearings is about 1/2" higher then the other bearings.  All of these factors seem to have put the W8 beams in torsion.  So now the occupants of the enclosure feel the enclosure sway.  How can this swaying be helped?  Will stiffeners in the W8 beam help with the swaying?

 

[JAE]

If the sway is caused by true torsional twisting of the W8 or W10 beams, vertical stiffener plates between the flanges of the beams will not reduce torsional deflection at all.&nbsp;&nbsp;If the deflection is caused by webs bending such that the flanges move laterally relative to each other (this would primarily be at the column bearing points) then stiffeners located directly at each column might help some.<br><br>If it is torsional twisting, the best way to stiffen wide flanges is to provide cover plates, welded across the flanges which convert the I shape into a box shape.&nbsp;&nbsp;Open I shapes, channels, slotted pipes, etc. have very small torsional stiffnesses.&nbsp;&nbsp;By converting to a box shape, the stiffness is greatly magnified.

 

[JC]

mann,<br>It's too bad that you can't send a sketch of the framing plan.&nbsp;&nbsp;But, the way I visualize the problem, is that you may be getting torsion in both the w8x18s anf the w10x26.&nbsp;&nbsp;The best way to eliminate this problem is to add one or two beams perpendicular toand between the w8s and w10 to tie them together.&nbsp;&nbsp;Also, x-bracing in horizontal plane between the two beams will help.