Seismic Response Analysis Of Large Elevated Pile Foundation

The elevated pile foundation, as a common substructure of the long-span bridge, has always been the vulnerable part of the structure when under seismic loads. Being conscious of the huge mass of the pile cap and scouring effect of elevated pile foundation, the seismic response analysis of the large high-rise pile cap foundation has been discussed in this dissertation by linear elastic analytical method and nonlinear analytical method. The detailed content of the dissertation is as follows:1. In order to simulate the dynamic interaction between superstructure and substructure, the simplified two-particle model has been adopted to model the superstructure and substructure. Through the finite element analysis and numerical analysis of the single-pier-pile-foundation and the whole bridge structure, it shows that the seismic response of the pier would be remarkably enlarged when the mass of the pile cap being huge, especially when the natural vibration of the superstructure meets with the substructure.2. Provided the soil being elastic medium, the common simplified seismic models have been compared and analyzed and the elastic fixed model has been stated in detail in this chapter. Through the response spectrum analysis, it shows that 6×6spring model deserves no good accuracy compared with the lumped-mass model. And equivalent fixed model shows more inaccuracy when analyzing the seismic response of the pile foundation. However, elastic fixed model performs more accurate compared with lumped-mass model3. Taking the seismic soil pile superstructure interaction (SSPSI) into consideration, the seismic response of the large high-rise pile cap foundation has been analyzed by p-y curve method. And the difference of the results of the p-y curve method and m method has been stated. It shows that, the results calculated by m method show larger than the results calculated by p-y curve method, whatever considering the non-uniform excitation of the soil stratum. And the parameters of deserving the soil p-y curve have been compared and analyzed.4. In view of the SSPSI, seismic response of the structure under different scouring depth has been compared and discussed. It shows that the seismic response come through a peak before going down along with the scouring depth being increased. And seismic response of the pile foundation system has been analyzed when taking the local scour into account. It indicates that the worst pile behaviors more dangerous when considering local scour under seismic loads.At last, the further studies of these issues have been discussed.