Hello community. I want to extract the natural frequency (linear perturbation-> frequency) of a beam defined in a 2d section (length and height), then I give it a depth. I would like to neglect torsional effects and enforce the euler or timoshenko beam conditions (plane section remains plane etc.). How do I go about it? what element is most suitable?

I have tried the plane strain and plane stress elements however they produce poor modal frequencies when I compare them with beam elements of the same cross section. My rationale for selecting the plane strain or stress elements was because of the degrees of freedom (x and y). When i tried 3d continuum elements i couldn't figure out a way to remove torsional modes and other modes coupled with torsion.

Abaqus ​​​​​​​