Stress analysis including seismic analysis for zone D was done using CII on 12”, STD wall, CS water line on a pipe rack from chilled water tower to the main plant. Uniform seismic loads were calculated in accordance with ASCE 7 based on Rp=12 (Table 13.6-1) and used for calculating of stress.
(Piping in accordance with ASME B31, including in-line components with joints made by welding or brazing a=2.5; Rp= 12.0)

OPE cases that include seismic loads and differential displacement between structures were considered frictionless.

At the same time ASCE 7 para 13.4.1 limits Rp to max 6 for calculating of forces in attachments.
13.4.1 Design Force in the Attachment
The force in the attachment shall be determined based on the prescribed forces and displacements for the component as determined in Sections 13.3.1 and 13.3.2, except that Rp shall not be taken as larger than 6

This requires 2 stress runs with Rp=12 for stress and Rp=6 for loads on restraints. Similar recommendation is found in Bentley AutoPIPE (Item #3 Comment)
https://communities.bentley.com/products...-load-case.aspx

Loads on restraints from CII run with Rp=12 were reported to structural group as follows:
- Normal operating loads
- Seismic component loads from CII e.g. OPE1=[(W+T1+P1+U1+U2)-(W+T1+P1)] were conservatively amplified by the factor of 2 to account for dynamic affects and max Rp=6 for forces.
This approach resulted in relatively high seismic component loads on line stops and some guides with magnitude of 80.0 kN on LS and 30.0 kN on guides.
Pipe rack is designed for 20.0 kN on attachments and beams for only 10.0 kN (that looks unreasonably low to me), but structural group does not accept piping loads.
Questions:
1. Is above approach to stress analysis correct and seismic component loads on restraints amplified by the factor of 2 look reasonable?
2. What needs to be re-designed: line or structure (this line has importance factor Ip=1 and not deemed to be seismically critical, that means it can fail during earthquake and cause only some flooding)
3. If structural design remains unchanged, how these seismic loads can be reduced to satisfy load limitations?
4. If the failure occurs, what will fail first: line or structure and how this can be predicted? (Line has a few flanged joints)
5. We used piping guides with gaps to allow differential displacement between pipe rack modules. Can line stop with gap be used for the same purpose?

Sound like too many questions, but your expert suggestions/comments even on some of them will be greatly appreciated.
Thanks,

Vikoll