Non prismatic brick element/ nonlinear model

[sgs]

Hello,

I want to model a masonry wall with varying thickness. The material model is nonlinear.
I wanted to define nonprismatic brick elements with fiber section. (is this a good choice?)

However, I do not know how I should define the fibers for such elements whose sections are changing.any idea?
Also, when the element is not prismatic how I should calculate the mass to be assigned to each node?

Thank you