I have a pipe that run on a structure and on a rack.

i have to analyze earthquake load case.

For pipe the earthquake is 0.35g along the direction x and 0.35g along the direction y.

Client confirmed that during the earthquake:

The metal rack will move:

Direction X: 50mm

Direction Y: 70mm

The concrete structure will move:

Direction X: 80mm

Direction Y: 100mm


On the pipe i insert a uniform load U1=0.35g (X direction) and U2=0.35g (Y direction).

Th pipe rest on structure/rack with shoes having friction 0.35 and there are also some guides with gap=0.


QUESTION:

how to model the structure and rack seismic displacement under the pipe?

how do i consider the deformation of structure and rack under the pipe?


can i, for example, for each support insert a Cnode to a small rigid and for each small rigid associate a displacement equal to structure or rack displacement below the pipe?

If yes, in quake load case I will have

W+T1+P1+U1+D1 for X direction

W+T1+P1+U2+D2 for Y direction

Where

U1,U2 are 0.35g on pipe

D1,D2 are structure/rack seismic displacement


in this way, pipe support shoes will allow sliding by friction even if below it the rigid (structure or rack) moves. do you think it?s correct or do you have any other suggestions?


If yes: have I to consider structure and rack seismic displacements having same direction or opposite directions? Or both cases?


If no: how can I model this case?