I am modeling a masonry wall in ANSYS using "Simplified Micro modeling approach". That means that I model the bricks as solid elements, and then mortar is considered using COMBIN39 springs and its interaction with bricks is simulated using CONTA178 Node to Node contacts. I have tried varying number of substeps, auto load stepping, altering the convergence criteria among many other things but the solution run always terminates at a certain lesser-than-desired value of deflection. I fail to figure out what I am doing wrong? The graph of my resultant Load-deflection curve (blue) to the desired experimental curve (orange) is attached herewith.