When we do a static seismic analysis, we put construction nodes on the restraints and apply the building displacements as vectors on those C-nodes. We just have to make sure to catch all the restraints on the building section moving. Usually we do 2-4 orthogonal directions depending on the pipe routing (lateral to piping axis and into/away from pipe axis). For tank nozzles I resolve the tank motion to the axes of the nozzle (which rarely matches the piping coordinate system).