I have a client that has indicated both the PGA=0.32 (under the SITE CLASS heading and based on a geothermal report that was prepared for this Nuclear Site) and the REPONSE SPECTRUM DATA (including the Sa(0.2) that I am accustomed to for the static analysis) on their pipe skid drawings for their client.

With reference to the pipe stress calculation, is there any reason to indicate the PGA? It is confusing the local safety authority and they are asking if I have included it in the PSA report. I do not believe there is an input for PGA, even under the Dynamic Analysis.

We are assuming that because it is a nuclear plant, an in-depth study was carried out to identify the PGA to ensure safety of the processes that are associated with anything nuclear. However, the piping skids are not associated with the nuclear process, even though it is destined for this site.

If David or Richard could comment on this it would be great!

Thanks in advance

For all those Canadain subscribers of this FORUM, I am going to answer my own question!

I just read that the NBC-2015 (National Building Code) used to use the PGA and it was replaced by the Sa (0.2) in the 2010 version, although funny enough, the PGA is not an input in the current Seismic Wizard for NBC-2005.

Not sure why this is.

In theory, PGA corresponds with Sa at 0 sec and make sense to use it when construct the spectrum. Using Sa(0.2) as PGA would be conservative for high frequencies, maybe this was the intent.