Study Of Dynamic Characteristics Of Pile Base Isolation Structure On Soft Ground

Exsisting study shows that the soil-structure dynamic interaction can not be ignored in the structural seismic analysis. In traditional seismic calculation, foundation is often assumed as rigid, transmission of the reciprocating earthquake excitation on the influence of the structure response is ignored. Therefore, the results of the calculation inevitably have huge difference from the actual value.Based on the basic principle of soil-structure dynamic interaction of isolation structure. Shaking table tests for base-isolated structure on soft interlayer foundation were carried on. Based on the paramenters from model test, integral three dimensional finite element models considering dynamic response of isolation and non-isolation structure on rigid and soft interlayer foundation were established based on ABAQUS. The elastic half space simplified model has been optimized based on above. Main contents and conclusions are:(1)Vibration response of pile base isolation structure on soft interlayer foundation was analysed through shaking table test. Results show soft interlayer foundation significantly changes spectrum characteristics of the input motions. The effect of the base rotation is remarkable. The amplification effect of isolator’s angle acceleration of different input motions exists difference.(2)The law of the isolation structure seismic response was studied through comparing the results of the models on different kinds of foundations. Overall, natural frequency of isolation structure is reducing with the severity of the foundation soil from firm to soft, and the damping ratio increases significantly. The influence on the response of isolation structure is different when the foundation is different.(3)Integral three-dimensional finite element model of pile-soil-isolated and non-isolated structure on rigid and soft interlayer foundation were established. Results of model test and numerical calculation were mainly compared, and indicates under the condition of rigid foundation, In addition to certain conditions, the amplification coefficient law is consistent. Under the condition of soft interlayer foundation, with the peak acceleration increasing, the deviation of the peak at the top of pile caps and the soil surface becoming small gradually. The intension of the motions are weakened when passing the interlayer. It proves the natural isolation effect of soft interlayer foundation is well.(4)Based on the existing simplified calculation method of the isolation structure dynamic characteristics, simplified analysis model of pile-base isolation structure was established. Results from this simplified method were compared with those from the model test. It verifies the simplified calculating method can effectively predict the dynamic characteristic and the seismic response of the isolation structure in considering pile-soil interaction.