Spring elements vs Connector elements

Hi. I am trying to simulate a metallic frame, with a board of OSB connected to it by metallic fasteners.

I have done two different models:

First model: I used spring elements with linear behavior, with three degrees of freedom (translational directions at each node). I gave a high stiffness in order to consider the springs rigid.

Second model: I used connector elements with linear behavior, with type Cartesian (just to have translational CORM), and considering elasticity rigid.

When I observed the results for each model, I observed that in the second model (with connectors) I had displacements in the Z direction (out of plane displacement), like a twist of the panel (rotated around a vertical axis). Because I am applying only a horizontal force on the top of the metallic frame (not in the panel), I am not understanding why this happen.

With the spring elements the model behaves like it should, but I want to simulate nonlinear behavior of the spring, and for now I don’t know how to do it…

Many thanks.

Regards,

Ricardo Dias.