Modeling truss member

[yhu2007]

I'm doing another truss bridge analysis using STAAD. My question is: Should I use "MEMBER TRUSS" to model truss all just usual beam element?

When I use beam element, some of the truss members will get large Mx or My, Mz. When I use truss member, I'll get many "instability at Nodes XXX" warnings.

 

[edward1]

I have found the best way to model truss bridges using STAADPRO is to use beam members for top and bottom chord and truss members for the bracing. This has given me deflection results that are closest to reality. Be sure to use the appropriate support condition to model a pinned support or roller support.