geometric nonlinearity

[tangzhen]

I want to do some analysis about geometric nonlinearity in a structure built with truss element, however I get the linear result . so how to solve this problem.
when I use the corotTruss element, I get the zero result , in this problem, an earthquake load is applied to the whole model. Is there any command I have to use to do the geometric nonlinearity analysis.
thanks a lot.

[mhscott]

Not clear what your problem is from "I get zero result", but try using multiple corotTruss elements per member.