Verification research on inelastic seismic behavior of soil-foundation-structure system

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The objective of the research project is to verify the input energy dissipation of earthquake motion at the base in soil-foundation-structure systems by on-site observation and test, SSI analysis and theory, with specific focus on the neighborhood inelastic behavior of soil. The observation research includes aftershock observation and the post-earthquake damage evaluation after Niigata-Chuuetsu Earthquake, October 2004, which was conducted with a specific research objective on identification of input loss of base motion at the foundation and neighborhood soil. A strong motion with very high spectral intensity was recorded during the main shock at K-net Ojiya station. Using the record as the base input motion to structures, large inelastic displacement responses were calculated, although the observed damages to reinforced concrete buildings seemed to be generally less than those in the calculation. The aftershocks were observed at a free field and in a school building nearby the K-net s … More tation to identify the difference at these sites. Relatively high aftershock up to the level 2 of the design motion in the Building Standard Law was obtained, where the input motion into the building was obviously reduced from those at the free field and the K-net station, which might be due to the input loss or soil-structure interaction at the neighborhood foundation. The main shocks recorded at the K-net and the JMA stations were assumed as possible input base motions to the structure, while the observed damages to the structure were compared with the calculated responses. It may be concluded from the analysis that the intensity of the main shock into the structure was obviously much less than that of K-net and probably also less than that of JMA. An on-site static pushover test on a school building in Ojiya was also conducted, from which inelastic behavior in lateral resistance at foundation level was identified. Analytical model is developed which fairly simulates these observation and test data. Input losses due to these effects are approximated in a general practical form Less