What would be the proper choice between shell and frame for modelling 1.2m x 0.6m vertical element?    In a building I am studying expansion joints. All columns are 600mm dia circular. Except some vertical elements 1200x600mm.   1) The question is what system for seismic behaviour you would consider as per ASCE? shear wall or frame?    2) How would you model 1200x600 as frame or as shell?