Development of Site Classification System and Modification of Design Response Spectra considering Geotechnical Site Characteristics in Korea (II) - Development of Site Classification System

In the companion paper (I-Problem Statements of the Current Seismic Design Code), the current Korean seismic design code is required to be modified considering site characteristics in Korea for the reliable estimation of site amplification. In this paper, three site classification methods based on the mean shear wave velocity of the top 30m , fundamental site periods and bedrock depth were investigated and compared with each other to determine the best classification system. Not enough of a difference in the standard deviation of site coefficients to determine the best system, and neither is the difference between the average spectral accelerations and the design response spectrum of each system. However, the amplification range of RRS values based on were definitely concentrated on a narrow band than other classification system. It means that sites which have a similar behavior during earthquake will be classified as the same site category at the site classification system based on . The regression curves between site coefficients and described the effect of soil non linearity well as the rock shaking intensity increases than the current method based on . Furthermore, it is unambiguous to determine sue category based on when the site investigation is performed to shallower depth less than 30m, whereas the current is usually calculated fallaciously by extrapolating the of bedrock to 30m. From the results of this study, new site classification system based on was recommended for legions of shallow bedrock depth in Korea.