Site Amplification Factor and Site Classification for Seismic Demand

Site Amplification Factor and Site Classification for Seismic Demand

The average shear wave velocity or the average SPT-N value of the upper 30 m of a soil deposit,(30) S V or N 30 , is an important parameter used in classifying sites in recent building codes. Based on these site classification criteria, the site response coefficients, Fa and Fv, were used to take into account the site amplifications of ground motion or design earthquake. The site response coefficients used in Taiwan building code were adopted from the U.S. building code provisions, which were based on empirical data for ground motions up to 0.1 g, and on the theoretical and laboratory results for larger motions. The TSMIP(Taiwan Strong Motion Instrumentation Program) array provides significant new sets of empirical data up to 0.5 g or even higher. These data together with recent site characterizations based on the investigation program of the CWB TSMIP sites provide empirical estimates of the site coefficients for different site classification. This two-year study has performed a detailed comparison of empirical site coefficients implied by the TSMIP earthquake data with those specified in the current code provisions.