Stress-resultant model for beam-column elements

[blaiman]

I've been working on a beam-column element formulation which has 22 DOFs per element such that member buckling as well as local buckling can be captured. One of the problems I am having with this formulation though is that I need to figure out how to incorporate a stress-resultant material model which can represent the bending of the plates for an I-section.

One obvious option is to incorporate a new material model similar to the J2Plasticity model under the NDMmaterial library for use with beam-column elements. However, I came across the command "Bidirectional" under the wiki which looks like it has potential to what I might be looking for. Does anyone know if following this route in creating, say uniaxial, material model with the characteristics of "Bidirectional" would be worthwhile or looking into for my particular element? Any input would be greatly appreciated!