Dynamic Analysis of a Spring-Asphalt Three-Dimensional Isolation System Based on Cyclic Simple Shear and Shaking Table Tests

Damping is one of the important issues related to isolated structures, including the newly proposed low-cost spring-asphalt isolation system. In this study, the damping properties of the system in terms of displacement dependence, frequency dependence and temperature dependence were studied by a cyclic simple shear experiment. Then, the direct least-square method was used to identify the damping properties from the experimental data. Furthermore, to validate the effectiveness of the damping device, a modal analysis was conducted based on multi-dimensional shaking table tests. The results indicate that (1) the hysteretic curves are similar to an ellipse, which means that the asphalt shows characteristics of viscoelastic materials; (2) the damping properties are positively related to the loading frequency and inversely related to the temperature and displacement; and (3) asphalt can provide adequate damping and reduce the displacements of the superstructure by nearly half. On the basis of the experimental test results, an analysis of the modal information with multi-dimensional input is also presented.