triangular trusses
triangular trusses
(OP)
I have a long span (120') porte coche roof truss that is triangular in cross section. There are two bottom chords, one top chord of pipes, with pipes web members tying everything together.
My question is this: does anyone have a reference for designing such a truss accounting for overall stability, especially lateral-torsional buckling of the whole truss?
Any reference help is greatly appreciated.
My question is this: does anyone have a reference for designing such a truss accounting for overall stability, especially lateral-torsional buckling of the whole truss?
Any reference help is greatly appreciated.






RE: triangular trusses
Curious as to what others think here.
RE: triangular trusses
RE: triangular trusses
RE: triangular trusses
RE: triangular trusses
It sounds like you're worried about the top chord flexurally buckling about a vertical axis.
Like one of the others typed, you could do an eigenvalue buckling analysis if you have a program like SAP. Just make sure you do a simpler model first to make sure you know what it's doing and how to use it.
You could also use the AISC Appendix 7 Direct Analysis Method. Explicitly model the top chord to be out-of-straight (bent laterally), use the reduced stiffnesses of the DAM, and run a rigorous second-order analysis. That should tell you if it's stable for the required load combos. Just looking at your ratio of second-order to first-order deflections, forces, etc., will give a good feel for the truss stability.
It would be interesting to see how the eigenvalue approach and the DAM approach compare.