Experimental Investigation of Seismic Damage in RC Frame Structures With Soil‐Structure Interaction Using Wavelet Packet Transformation

In existing studies, researchers tend to use peak values as indicators that directly reflect the time‐frequency characteristics of structural responses. However, there is limited research on the time‐frequency analysis of structures considering soil‐structure interaction (SSI), making it difficult to intuitively obtain information about structural vibration intensity, fundamental frequency, and duration. Therefore, using the results from a previously conducted shaking table test of a 12‐story frame structure with SSI effect, wavelet analysis is employed to perform wavelet packet transformation on the time‐history response signals of the frame model. This process obtains the corresponding time‐frequency relationship and the maximum energy variation index of each floor, which can reveal the variation patterns of structural responses in the time and frequency domains comprehensively, and evaluate the structural damage state under various earthquake excitations. In this present study, the experimental results of the 12‐story frame structure are further analyzed in time and frequency domains, decomposition and reconstruction of acceleration responses, energy distribution of each frequency band, and total energy ratio. The results show that, firstly, the shallower the depth of the soil, the larger the seismic response, and the response at the pile foundation is larger than that at the free field, indicating that SSI effect amplifies the response of the soil. Secondly, the acceleration amplitude of the SSI system is smaller than that under fixed‐base condition, and the SSI effect reduces the overall energy of the structure. Finally, the middle levels of the structure have the largest probability of maximum energy variance index, therefore appropriate strengthening measures should be considered in the seismic design of the structure.