Which Rp for large diameter pipe ?

[4Pipes]

Please could somebody advise on which Rp values to use for large diameter pipe. 1.25 for cast iron pipe and 3.5 for small bore copper and steel pipe which would seem logical given that Rp is a measure of energy dissipation due to plastic deformation.

However, what happens when the supporting structure cannot develop the forces necessary to plastically deform the pipe necessary to absorb the energy of motion. Is it still reasonable to classify welded steel pipe as high deformability ?
Should a high Rp be used for large diameter thick walled steel pipe. Say 30” diameter x 1.5” wall. The section properties of the pipe are very much higher than sections in the supporting structure. The supporting structure may even be portalized in some directions. My judgement would be to class the pipe as low deformability because the pipe is going to be the last thing that bends. I would value any comments.

 

[stanier]

I am a newcomer to this forum and would like to learn as the thread is replied to. Could you please explain the term Rp and where it appears in text, books, codes, software etc.

 

[4Pipes]

Rp is the Component Response Modification Factor specified in UBC97 and IBC2000. I think it was known as Rw in UBC94. (Rp and Rw mean the same in principle but are not numerically the same). I understand it to be a measure of the energy absorbing capability or ductility inherent in a particular component. The values I quoted above are from IBC2000 for "low deformability" and "high deformability" pipework respectively. The higher Rp gives very much lower design loads so is the value of choice. I'd very much like to know some background to the building code values.

 

[stanier]

Hi 4 pipes,

Thanks for the response. I have come across the term in a FEMA document FEMA302. FEMA as I understand were commisioned by BSSC to recommend provisions that were adopted by IBC. You can download from FEMA's website. FEMA may be able to answer your question