Modal analysis for 3D beam

I am writing matlab code for the modal analysis of3D beams with different boundary conditions.

1. Fixed - guided beam

2. Simply supported - Guided beam

3. Guided - Guided beam

Initially I developed the modal analysis code for cantilever beam and checked it. It works well Now I want to modify that code in order to suit for the above cases.

How to do that? Anyone can help me

[KSSV]

First place this is not a matlab question. A structural problem you want to code in matlab.

You want to use FEM? How you have done 2d analysis?