A NUMERICAL STUDY ON SLIDING OCCURRENCE ACCELERATION FOR SLIDING BASE ISOLATION STRUCTURES

The occurrence condition of sliding is an important parameter for the dynamic response characteristics of the sliding base isolation structures, and it provides the theoretical basis to the performance based structural design of the sliding base isolation structures. A two-degree-of-freedom system model is adopted to simulate sliding base isolation structures. Base on the time history analysis method, the influence of various structural parameters (including natural period, mass ratio, and sliding friction coefficient) and ground motion parameters (including characteristic period of response spectrum and pulses of near-fault ground motion) on the sliding PGA are investigated. The results indicate that the structural parameters exhibit a stronger influence on the sliding PGA than that of the ground motion parameters. The sliding PGA versus natural period relationship curves of the isolated structures consisted of 4 segments, i.e., descend segment, horizontal segment, ascend segment, and ascend initially then keep horizontal segment. The sliding PGA decreases with increase in the mass ratio for the structures with natural periods smaller than 1.4 s, and increases with increase in the mass ratio for the structures with natural periods larger than 7.8 s subjected to the considered ground motion groups. The sliding PGA increases in an equal proportion with the increase of the sliding friction coefficient. An empirical expression to predict the sliding PGA is proposed using a piecewise linear fitting method. The calculated results of sliding PGA for the multi-degree-of-freedom structures using the proposed expression and time history analyses are in a good agreement. The results provide a basis for the following research on the sliding occurrence condition and the structure design of the sliding base isolation structures.