SEISMIC POUNDINGS MODELED AS THE NON-LINEAR GROUP IMPACTS BETWEEN ASYMMETRIC STRUCTURES

摘要

Eccentric poundings between adjacent structures are usually induced in severe earthquakes. In this paper, the eccentric poundings between an asymmetric structure and its neighbor barrier under harmonic earthquake excitation were modeled as non-linear Hertzian impacts. The impact force depends on the 3/2 power of the relative displacement and the relative contact stiffness of the asymmetric structure and the barrier. The coupling effect between the horizontal motion and the rotational motion of the asymmetric structure is considered. Fourth-order RungaKutta integration method is used to get the numerical solution for the asymmetric structure. The maximum impact velocity and the maximum angular velocity within 40 excitation periods are used to indicate the dynamic behavior of asymmetric structures under earthquake excitation in the numeral analysis. In general, the poundings have very large influence on the motion of the asymmetric structure, in some cases even changes the motion pattern of the asymmetric structure. More importantly, we found that the group impacts, which are never occurs for symmetric structures, are a common type of pounding behavior of asymmetric structure. The pattern of the group impacts depend on the damping ratio, the natural period of the asymmetric structure. In addition, the largest responses of the asymmetric structures are always induced when the nature frequency of the asymmetric structures is very close to the input frequency of the ground excitation nearby, but not necessarily at the case when the nature frequency of the asymmetric structures is equals to the input frequency, which is consistent with experiment results.