if i well understood.

if i have a pipe running from a structure (on structore there are 5 pipe supports) to a piperack (on piperack there are 6 pipe supports)

i will analyze with different caesar models:

Model_1) i analyze only seismic (0.35g x direction and 0-35g for y direction) and structure don't move.

model_2) i analyze only relative displacement between structure and piperack. if structure moves 100mm and piperack moves 60mm, i will consider both case displacements have same directions both case diplacements have opposite directions.
So:
model_2-subcase_A): 100+60=160mm for structure and 0mm for piperack
model_2-subcase_B): 100-60=40mm for structure and 0mm for piperack

BUT!

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