In Opensees, why reinforced concrete beam-column joint is assumed as a parallelogram?

[kaustavsengupta]

I have included an inelastic Joint2D element in my RC moment frame building for RC BC joints. My moment frame has seismic and gravity loading,

A. Which option is correct?

Option 1. Is the RC BC joint modeled as a parallelogram considering shear deformation is more critical than flexural deformation? OR

Option 2. Is the RC BC joint modeled as a parallelogram considering shear deformation is more than flexural deformation?

B. Why can't we model the RC BC joint for flexural deformation? Is it related to more deformation or critical deformation? or critical forces?
Here critical means that cause permanent failure even without loading

C. If there is only gravity loading, we need not model the RC BC joint as a parallelogram. We can model it as a trapezium, right?

Kindly reply.