Ken, All great points and I should have pointed them out when I referenced the USGS site. Making assumptions for any of the categories listed would be the same as guessing on water flow data for hydraulic calcs. Most of the information, if not all, in this area is shown on the structural drawings for new buildings. If it is an existing building, then it's a lot of phone calls.
Marc Walter, SET Sprinkler Design Services 780 6th Avenue Seaside, OR 97138 (503) 956-4019 -----Original Message----- From: Sprinklerforum [mailto:[email protected]] On Behalf Of Parsley Consulting Sent: Tuesday, November 11, 2014 9:19 AM To: [email protected] Subject: Re: Seismic Ss Values Brian, The first concept I present when I teach seismic protection for sprinkler systems is to avoid doing the work of the site engineers, soils engineers, structural engineers, or architects. Heading down that path increases your chances of sitting in the witness chair to defend what you've done. A decided negative all the way around. As for the process itself, it's not quite as simple as it used to be, as I'm sure you've learned. The USGS software forces you to designate applicable design codes, the appropriate soil classification, and perhaps the risk category or earthquake hazard level as well, prior to determining the Ss value for you. Steve Leyton is correct, in that finding the exact lat/long of a project site is fairly easily accomplished thanks to numerous websites. The one I use most frequently is latlong.net. There are nine different design code reference options in the USGS software. I know which one of those options is applicable here in California, however, unless you're sure of what's applicable for your specific project the results might not work out the same. The site soil classification could be better or worse than the default value for the calculation, which is "D". A lower letter (A-B-C) shows a much more stiff soil, while a higher designation (E-F), shows a much less resistant to motion parameter. You may have to enter a "risk category" which identifies the building use, or the "earthquake hazard level", which has four separate categories, or a custom set of parameters to generate the information. Now if you can, with some degree of accuracy, establish those variables, then the USGS process can give you a reasonably accurate Ss value. If you can't, then why are you trying to do that in first place? The only reason I follow the process is to verify some value on a set of plans - either from a sprinkler contractor or a structural engineer - that just doesn't match what I've seen before in a specific area. And, when I come up with a different value, my question is always, "I came up with this value, which is different from yours. Can you check my figures/parameters to see where we might be coming up with different numbers?" I'm not trying to tell you to run and hide, however I am suggesting that you're taking on a liability that doesn't match the work you're doing. The above is my opinion as a member of the hanging and bracing committee of NFPA 13, and doesn't reflect the official position of NFPA, which is contained in the standard, or that of anyone other than myself. sincerely, *Ken Wagoner, SET *Parsley Consulting*** *350 West 9th Avenue, Suite 206 *Escondido, California 92025 *****Phone 760-745-6181* Visit our website <http://www.parsleyconsulting.com/> *** _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
