Buckling and lateral torsional bucklin

[LMW.dk]

Hey guys i have a question. I have a portal frame like the one attached, where i have timber at 1070 at the rafter. My question is can those timber construction be regarded as bracing against lateral torsional buckling ( Moment) and buckling ( Normal force) pr 1070

 

[271828]

I assume this is a steel frame. The answer is probably "not by themselves."

Depending on the diaphragm stiffness, the purlins might provide a relative lateral brace for the top flange. See the AISC Specification Appendix 6 and the "Fundamentals of Beam Bracing" paper by Yura.

Presumably, some parts of this frame have negative moment. A lateral brace must attach near the compression flange, so the purlins don't provide that in negative moment regions. Theoretically, they could provide torsional braces, but it's hard to envision how this could be accomplished in reality. In negative moment regions, you would need to add a diagonal member from the purlin to the bottom flange of the rafter. That might qualify as a torsional brace or a lateral brace per Appendix 6.

 

[Lomarandil]

All of what 271828 said, but on top of that, the timber connections will make meeting stiffness requirements very difficult.



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The name is a long story -- just call me Lo.