This question would be good for the seismic bracing experts in the group: NFPA 13 and ASCE/SEI 7 address the Component Response Modification Factor (Rp) as a ductility of the system. It comes into play when determining the seismic design force using the ASCE/SEI 7 method (not the simplified method used in NFPA 13).
NFPA 13 states several times that this factor (Rp) is 4.5 for steel systems (NFPA 13-2016 A.220.127.116.11.1 and E.3). The only mention of plastic pipe systems is in Annex E.3 where it states an Rp value of 4.5 for "high-or limited-deformability piping with joints made by threading, bonding, compression couplings, or grooved couplings", and an Rp value of 1.5 for "low-deformability piping such as cast iron and non-ductile plastics". Is a Response Modification Factor of 1.5 suitable for CPVC pipe?
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