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Bracing a W section

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Anantha Narayan wrote:
"Greetings
I am analysing an existing scoreboard for future expansion. It has a horizontal truss with W14x30's being braced by 2 1/2 x 2 1/2 x 1/4 angles (at the top and bottom flange).
Would be adequate to use a section having twice the section properties as the 2 1/2 x 2 1/2 x 1/4 or are there any other ways to model the same.
I am using ETABS for my analyses.
Thanks
Anantha"
 
 
Anantha,
That's how I would model it.
 
Taking a step beyond your question, if these small angles are only welded (parallel to each other) to the flanges of the W14's and not back to something solid, then I wouldn't consider the beams braced.  In my mind, a pair of beams can brace each other if there is a member between them which prevents torsional displacement (twisting).  In this case, a W14 or W12 attached with sufficient rigidity to each beam would prevent twisting; and even if both beams moved laterally, absent axial load they cannot fail in lateral-torsional buckling.  But two small angles top and bottom do not accomplish this.
 
But, the picture I am drawing in my mind may not look much like your scoreboard.
 
HTH,
Mike Hemstad, P.E., S.E.
Meyer Borgman Johnson
Minneapolis, Minnesota