David Diehl indicated on June 98 how to model flexible coupling ( volume 25), David dismissed using Expansion Joint, but in my case i have too rigid model for OPE EXP , because if i put a flexible coupling i suppose it will expand all gap (3.2 mm) due pressure thrust but it wont have a flexible relief around lateral Tee restraining for expansion. this model is failing taking an expansion joint in flexible couplings for OPE and EXP