Studies On Seismic Analysis Of Simply Supported Isolated Bridge In High-speed Railway Subjected To Multi-dimension And Multi-support Earthquake Excitations

Since 1964, the Japanese built the world’s first high-speed railway(Tokaido Shinkansen),the fast transport and economic benefits achieved won the recognition of many countries in the world, and they have added to the research and development of high-speed railway. In the construction of high-speed railway, due to traffic safety and vehicle speed requirements, the route for most of the bridge used in the form of straight, which makes in high-speed railway bridge accounted for a great part. The importance of the bridge for high-speed railway traffic safety is self- evident, once the high-speed railway bridge to be damaged in the earthquake,it will cause great economic losses. At the same time,it also has a great negative impact on the relief work and reconstruction after the earthquake. It is necessary to analyze the existing high-speed railway bridge structure in order to ensure the safety of the high-speed railway bridge structure in earthquake.Nowadays, the seismic isolation usually to be used in the current bridge design in order to meet the isolation requirements. The simple supported box girder bridge is used as the main beam in the high-speed railway bridge,and this kind of bridge still has the characteristic of large longitudinal span, and the structure form is easy to be affected by the traveling wave effect in the earthquake. Also, the multi-dimensional seismic action will also be larger influence on high-speed rail bridge structure, structure under Multi-dimension and Multi-support Earthquake Excitations will be more complicated. For long-span Bridges and complex structure,should consider Multi-dimension and Multi-support Earthquake Excitations,that will make the assessment of the structure will be more accurate.The article based on a high-speed rail bridge project, which using high damping friction isolation bearing, and usingthe the displacement time history method to doing nonlinear time history analysis. The main research parts as follows:(1)Using finite element software to establish the bridge model and the non linear dynamic time history analysis of the bridge is carried out. It show that the vibration isolation performance well. Researching the influence for the isolated effect of the bridge when considering nonlinear,the result shows that considering linear of the bridge will overlook the effect of isolation,nonlinear should be consider when researching the isolated bridge.(2)Using nonlinear dynamic time history analysis to research the internal force and acceleration response of the bridge under consistent and multi-support excited, as well as analysis the isolation bearing displacement and energy consumption situation. The results show that considering traveling wave effect bad for the acceleration of the deck of the bridge,and considering traveling wave effect is good for the pier bottom shear、moment of the pier bottom shear、the pier top acceleration、displacement of pier top and displacement of the deck,especially for the displacement of the deck. The traveling wave effect is generally beneficial to the seismic isolation bearing, but the effect is not big. In addition, compares to the traveling wave effect by excited the earthquake from consequent or reverse. It show that the excited direction obviously influence the performance of the bridge isolation bearings.(3)Using methods of nonlinear dynamic time history analysis to analysis isolated bridge,excited the seismic waves in single、double and three propagation directions,the results show that it has increase in the acceleration of the top of pier, the deck acceleration and displacement of bridge deck and the shear and moment of the pier b ottom reduce, and it has small influence on displacement of bridge deck. After cons idering the excited of multi-dimension and multi-support seismic, the responses peak of the bridge are same as multi-dimension excited, but it will form a different degre e of numerical fluctuation in each pier.When isolate bridge suffer two-dimension earth quake,with the increasing of the wave velocity,internal force of the middle pier、accele ration of the bridge、displacement of the bridge all same as one-dimension excitation.When isolate bridge suffer one-dimension earthquake,with the increasing of the wave velocity,internal force of the middle pier、acceleration of the bridge all different with o ne-dimension and two-dimension excitation,displacement of the bridge all same as onedimension and two-dimension excitation.