Abstract Summary
In the seismic design of building structures, the natural period and damping ratio are important parameters that greatly affect the response of the building. However, most of the seismic observation data for actual buildings are affected by the dynamic soil structure interactions (SSIs). Therefore, a method for estimating the effect associated with the SSI from measurement data in actual buildings is required. In this study, as one of the methods for estimating the vibration characteristics of the SSI system and those of the building itself from the actual data, we estimate the vibration characteristics of the SSI system by applying the modal error iterative correction (MIEC) method, which is a general purpose inverse analysis method for input output (IO) systems, to the sway rocking (SR) model. The parameters identified by the MIEC method are collectively identified as the story stiffness and damping ratio of the building and dynamic soil springs. In addition, by identifying each parameter, we evaluate how the horizontal and rocking interactions in the SSI system affect the vibration characteristics of the building itself. The novelties of this study are that the parameters of each story of the super structure and the dynamic soil spring are estimated collectively. Moreover, the parameters are estimated considering not only the first mode but also the higher modes. First, an overview of the IO systems to estimate the vibration characteristics using the MIEC method is presented. Next, a seismic response analyses are conducted using a numerical analysis model simulating a three story reinforced concrete (RC) building supported by pile foundations. The proposed identification method is applied to the seismic response analysis data. Then, estimation accuracy of the parameters based on this method is verified for the parameters set in the analysis model. Finally, the proposed method is applied to the large shaking test data of the RC structure specimen supported by the pile foundation performed at E Defense which is the largest shaking table facility in the world. In the experiment, vibrations were applied from small amplitude to large amplitude level for seismic excitations that greatly progressed the plasticization of the specimen. By comparing the results of the parameters estimated using the numerical analysis of the SR model and the MIEC method, it was confirmed that each parameter could be estimated with generally good accuracy. By applying this method to a large shaking table test of the SSI system and identifying their parameters according to the amplitude level experienced, the variation characteristics of the SSI system and their changes can be investigated. As a result, it was found that the natural period and damping ratios of the first and second modes tended to increase due to the influence of SSI. On the other hand, the variation of these effects according to the amplitude level was found to be relatively large in the damping ratio than in the natural period. In the future, we plan to study the vibration characteristics of an actual building by applying this proposed method.
