plane strain vs plane stress

where can I use plane strain and plane stress?
if I have a portal frame : column 600x600 mm and beam 600x800mm, which element type is suitable?

Forums: 

Dear Salahqudah,
Plane strain and Plane stress are two simplification structural models for the modeling of 3D problems, in which:
- Plane strain modelling: strain in Z-direction is neglectible
- Plane stress modelling: stress in Z-direction is neglectible
For a beam, plane stress is normally used, assuming that the stress in Z-direction can be neglected;
otherwise 3D modelling is advisable.
With reference to the element types, for 2D models, quadrilateral elements with quadratic interpolation is recommended.
For 3D models, brick solid elements with quadratic interpolation is recommended. 
Kesio Palacio
TNO DIANA support team

By Kesio Palacio