Collective Identification of Superstructures and Dynamic Soil Springs Considering the Effects of Higher Modes Based on the MIEC Method

The natural period and damping ratio are essential parameters that significantly impact the seismic response of buildings. Most recent seismic observation records have indicated that buildings are also affected by the dynamic soil-structure interaction (DSSI). In this study, we propose an identification method of vibration characteristics considering low-to high-order modes using the modal iterative error correction method and evaluate the influence of DSSI. First, we confirmed the validity of the proposed method using a numerical analysis model. Next, the proposed method was applied to the large shaking table test, and the stiffness and damping of the specimen were identified. The identification results for the test showed that the stiffness of the building or soil spring decreased, and the damping ratio tended to increase with the increase in the maximum deformation experienced. Upon evaluating the influence of DSSI on the foundation in the fixed condition, the effects of the first and second modes on the natural period were found to be more pronounced than the third mode. When the maximum deformation experienced increased, the natural period did not considerably change, whereas a part of modal damping ratios exhibited relatively large fluctuations.