Shaking table tests on the modal of a multi-story isolated structure on the ground with softer interlayer

Based on shaking table tests on the model of a multi-story isolated structure on the ground with softer interlayer, the dynamic characteristics of the structure and the seismic behaviors of the ground were studied. The superstructure acceleration responses and turning effects of foundation and isolation layer were analyzed. The turning effects on the isolation effectiveness were investigated. The test results show that the ground motion is obviously weakened due to softer interlayer, soil-structure interaction (SSI) is of signifigant effect on dynamic characteristics of the isolated structure on softer interlayer ground. Its first order natural frequency is reduced and the damping ratio is increased. The turning effects of foundation and isolation layer can be induced on the softer interlayer ground by SSI. The isolation layer can amplify the rotational acceleration response of foundation, depending on the type of the input earthquake motion. SSI can increase or decrease the seismic response of isolated structure on softer interlayer ground. The isolation effectiveness is closely related to the intensity of turning effects of isolation layer. When the turning effects of isolation layer is enhanced, the amplification factors of floor acceleration amplitudes of the isolated structure are increased, and the isolation effectiveness is reduced. When the turning effects of isolation layer are weakened, the amplification factors of floor acceleration amplitudes of the isolated structure are similar to those in the case of a rigid ground, and the isolation effectiveness is rather good. © 2015, Chinese Vibration Engineering Society. All right reserved.