Regarding the seismic analysis using dynamic tool of response spectrum method, I need some advice from specialists who have many experiences.

Our piping is laid from a HRSG structure to Turbine building via a pipe rack.

when we need to use seismic spectrum, C-II can generate a spectrum data by structural code like UBC. as far as i know, the spectrum generated automatically by C-II is ground response spectrum then the spectrum can be used if the piping is located on ground level.

but in my case above, should amplified response spectrum by each elevation attaching the piping be applied instead of ground spectrum? because our piping is on three structures.

of course, three structures may have different spectrum then the enveloped spectrum including the three spectrum has to be applied.

generally does the architectural team supply the data through the structure analysis?

If the data is not available, are there big discrepancy between the results using ground spectrum and amplified(floor) spectrum?

I'm looking forward to listening to valuable advice from specialists.

I agree, your piping would experience an amplified spectrum. You have two choices that I see:

1) Obtain the amplified spectra from your structural group to use as input to your CAESAR II model.

2) Model the structural steel in your CAESAR II model and use CNodes to connect the piping to the steel. This will allow the ground spectra to excite the structural supports. (The CNodes are internal restraints and would not be excited directly by the ground spectra.)

In my opinion, in alternative 1 and considering your particular case of 3 structures, you must consider also the different seismic displacements of group supports belong to different structures.
I mean even the supports can be at the same level but in different structures, it is likely they will be subject to different imposed displacements under a seismic event.
In fact for a structure and a level the supports are subject to a spectrum considered in phase for those supports, but for two structures and a level, you have two groups of supports, subject to different spectra which are out of phase in the worst case. It is what is named in literature Seismic Anchor Movement- SAM.

That's why I think the alternative 2 is better, even is hard in practice and time consuming.