I have designed a 80m box truss with StaadPro. For the top chords that are in compression, do I need to specify their Lz to be equal to 80m? If I do that, the top chords will fail terribly due to slenderness. Is it a valid assumption to default the Lz for the top chords to the member length between nodes in this circumstance?
I have attached the relevant file; will appreciate some advices.