An Introduction to Seismic Design Categories for the Seismic Design of Structural Buildings

May 15, 2017 Abdul Siraj, P.E.

The International Building Code (IBC 2012) is used to calculate the seismic forces acting on a structure during an earthquake. The International Building Code (IBC 2012), Section 1613, specifies the following six seismic design categories (SDC): A, B, C, D, E, F. In addition to the six seismic design categories, International Building Code (IBC 2012), Section 1613.3.5, also defines four risk categories: I, II, III, and IV. The design spectral response accelerations, SDS and SD1, are parameters that are used to relate the seismic design category with risk category.  SDS is the design spectral response acceleration coefficient for short periods, and SD1 is the design spectral response acceleration coefficient for a period of 1-second. There is a relationship between the design spectral response acceleration coefficients and severity of the design earthquake ground motions at a particular location. Identifying the proper seismic design category is essential because it dictates what type of lateral force analysis must be performed as well as what type of lateral force resisting system must be used.