Expansion joint stiffness data in terms of trasverse and rotational stiffness can be obtained from vendors.This data can be used for modelling the expansion joint.The forces and moments obtained based on analysis(dead weight,thermal,seismic or spectrum etc.,) must be forwarded to the vendor for qualification of the Expansionjoint.Only when both Piping and expansion joint are qualified we can conclude that system is safe.

I agree with the comments given by the Moderator

thanks

c srinivas