Response Analysis Of High Damping Rubber Isolated Structure Under Near-Fault Earthquake

Owing to the fact that near-fault ground motion is featured with short duration, large amplitude and long-period velocity pulse, it imposes serious damage to buildings. As a new type of isolation bearing, high damping rubber bearing(HDRB) is added with large amount of high damping material, dissipating more seismic energy, so that it is widely used in baseisolation engineering. According to results of experiments, HDRB is sensitive to the loading frequency, which is related with loading rate. Therefore, it is of great theoretical and engineering value to study the dynamic response of HDR isolated structure under the nearfault earthquake.Firstly, the paper discusses the mechanical properties of high damping rubber bearing. The bilinear hysteretic model is introduced, and the mechanical parameters of the model are calculated through the horizontal shear test of the bearing. A rate-dependent constitut ive model of HDRB is developed based on the improved hyperelatic Zener model. The mechanical properties of HDRB at different strain rates is researched through the cyclic compressive-shear test of the rubber material. The relevant parameters in the model are determined by fitting the test curve, which provides the basis for the finite element analysis of the HDR isolated structure.Then, on the background of practical engineering, the study establishes HDR isolated structure based on the bilinear hysteretic model developed by SAP2000. With the nonlinear time-history analysis method, the structural responses such as base shear, story displaceme nt, story acceleration are compared between near-fault and far-field earthquake. The results show that the seismic response of HDR isolated structure under near-fault earthquake is much larger than that of far-field earthquake.Finally, ANSYS restart function is used to simulate the high damping Zener model. With the dynamic time-history analysis method, the seismic response differences between the Zener model and the bilinear hysteretic model are compared from many aspects, including story shear force, story displacement and horizontal hysteresis curve of the bearing. The results indicate that the rate-dependent high damping Zener model delivers better seismic isolation effect under the near-fault earthquake.