Seismic Design Category and Site Class are indeed two different things - although inter-connected in concept:
We have the Secondary Onsite Water Supply requirement from the BOCA days and now IBC codes which relies on the determination of Seismic Design Category (SDC) as the threshold to apply the code requirement in the hi-rise building. While I am not an engineer or credentialed designer this is the very basic form to determine SDC for a project (Under IBC Chapter 16) Seismic Design Category actually consists of the following three factors or variables that are part of the overall calculation: - Site classification (site soil conditions and engineering) - Anticipated ground motion - Local data or you may use general maps found in the IBC as to the risk and extent of ground movement for that locale - Occupancy category - IBC Section 1604.5 - A Table which puts a risk hierarchy on buildings based on value to the community and occupancy When a project does not perform site specific soil engineering analysis the IBC allows the assumption of a default site classification 'D' (IBC Section 1613.5.2) This may explain why a number of small sprinkler jobs often just say Site Class 'D' on them .. No soil engineering performed and opting to use the code default. The occupancy category is found in Table 1604.5 and most residential high rises will be Category II You put all those variables and factors into a blender and push blend and then puree and the answer will give you the Seismic Design Category for the project .. A value of C,D,E,F would then be the trigger to provide the secondary on-site water supply I have seen a lot of sprinkler shop drawings which cut and paste general data from the architectural plan cover page where there is the Site Class 'D' provided for purposes of footing depth and size. Somehow this piece of information ends up on the sprinkler drawings as SDC - Class D which is really incorrect but often times goes below the radar and does not affect outcome. If you have a project with something unusual about it then it's time to fire up the blender OR have the engineer provide you with the actual SDC - NOT the Site Classification. IMHO - TGIF Dave P. Fire Fighter with dreams of designing _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field)
