The question is long:

I am modelling a masonry wall in ANSYS APDL. The masonry units are "expanded" to half mortar thickness on each side and joined to the adjacent ones using Surface-to-Surface contacts. Bricks are assigned Drucker-Prager plasticity parameters.

After the first load step of vertical pressure is applied on the wall, the second load step is applied that pushes the wall laterally in-plane. (For the 2nd load step, the vertical motion of the top beam is restrained). When this push is applied:

1. If the contact cohesion value is less, the top beam (above the wall) slips and very little lateral (practically zero) slip is transferred to brick courses underneath.

2. If the contact cohesion is increased, the wall deflected shape is a good one but the stresses go as high as twice the compression and tension limits of brick that were used to define Drucker Prager's parameters. The pushover curve gives 10 times high strength for the wall than actual.

I cannot figure out the root cause of the problem and need someone to help. Thanks.