There are recommendations/requirements to not consider the frictional effects in piping seismic calculation.

See for example ASCE 7, 15.5.2 Pipe Racks, 15.5.2.1 Design Basis:
"[...] See Section 13.6.3 for the design of piping
systems and their attachments. Friction resulting from
gravity loads shall not be considered to provide
resistance to seismic forces."

Best regards.