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Re: HSS Truss Stability

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        A few years ago I designed something like this.  I don't remember the span and depth; but they were quite a bit larger, perhaps 80' and 66 inches or even larger.

        What we did was to use two top chords about 6 or 8 feet apart and a single bottom chord half way in between.  As  I recall, the planes of the webs were between 45 and 60 degrees from horizontal (closer to vertical than to horizontal); we had purlins between the top chords of each joist and between joists in order to span the metal decking parallel to the joist span.  All members were hollow structural members with 50 k.s.i. yield.  This configuration provides complete stability for all chords.

        Excuse me for being so vague about the details but it has been several years and I find it hard to separate what we actually did from what we seriously considered and rejected.  If you would like more details I could look it up and e-mail you privately.

        Hope this is helpful.


H. Daryl Richardson

Paul Feather wrote:

I am looking for additional resources / references regarding truss stability bracing.  I have architecturally exposed HSS trusses spanning 44 feet with a 42 inch depth.  The trusses are top chord bearing at the supports.  Top chords are continually braced, the desire is to have the absolute minimum bottom chord bracing in the span and at the supports.  The architectural goal would be no bottom chord bracing at all. Any references / methodologies of rational analysis for evaluating the brace requirements would be appreciated. Paul Feather PE, SE