Compression only element/support (NLLINK-GAP)

[jackyyau]

I am try to model a support, an element which is able to take compression only with the NLLInk GAP element, however it is found that the GAP element is able to take tension as well. Why?

 

[ElmerTheFudd]

The tension force is from the linear spring portion of the gap element. Gaps have a linear spring (when open), and a nonlinear spring (when closed).

 

[jackyyau]

According to the help menu from searching "GAP": Nonlinear behavior is exhibited only during nonlinear time-history analyses. For all other analyses, this link element behaves linearly.

Therefore the spring should be elastic for linear analyses like static analysis...

The question is still unresolved. How to model a compression only spring (passive soil support)? I expect the outputs of these compression only springs to be zero or ill-conditioned when these springs are under tension.

 

[kennyltk]

Dear ElmertheFudd, I am Jacky's friend. I have tried to increase the stiffness for non-linear spring and set the open to zero, also I set the stiffness for linear spring to zero, however the result is the same as that of no spring under compression, how can I activate the stiffness of non-linear spring?