What is meant by linear release and nonlinear release when working with boundary conditions?

[bojoka4052]

I have a bar element which was pinnned on one side and compressed on the other. Ive been told to change it to a nonlinear release so that the bar element can no longer take any compression. I've assigned tension-only property to the beam, but now the problem becomes nonlinear it seems, and takes much longer to run.

I am trying to understand what exactly is meant by release, what is the difference between linear and nonlinear release. And why does assigning tension-only property to the beam make it go from linear to nonlinear? The programme I am working with is a structural FEA programme, and not Abaqus, Ansys, Comsol or any of the other more popular ones.

 

[FEA way]

Tension-only behavior is indeed a form of nonlinearity. Several FEA codes offer no compression and no tension behavior that modifies the linear elasticity of the material. And I would stick with this option, I don’t think that end releases (usually used to introduce internal hinges) are necessary in this case.