Research On Dynamic Performance Of Railway Bridge With Seismic Isolation Bearing Under Train Load And Earthquake

Seismic isolation technology is usually used in structures and bridges. This method can prevent and dissipate the input energy of earthquake and reduce the acceleration response of structures effectively. However the LRB is rarely used in railway bridges. The railway bridge with tracks is hardly to analysis for several reasons such as vehicle structure, groups organizing and velocity of vehicles. So far, the performance of railway bridge under train load and earthquakes is not clear. And in China the velocity of trains is frequently accelerated, the smooth of tracks is restricting restrained. In order to apply the seismic isolation technology to high speed railway bridge and to insure the safety and satisfaction, the following content had been studied:1. The vertical and longitudinal coupling oscillation between train and railway bridge had been analyzed. It is simplified to be the multi-particle model. The isolated bridge using finite element model connect the vehicle and bridge system together through the longitudinal interaction force between the wheel and rail. Set up the train's dynamic equation through the force balance. The interaction force time history between wheels and tracks had been obtained. Multi degree of freedom model and forth and fifth order Runge-Kutta method is adopted when calculating the braking force time history. The bending and braking force time history had been second discrete transferred to braking force time history fixed node of structure to realize the space discrete. The time discrete is realized for the bridge dynamic analysis by the ANSYS. The result show that, when the train pass by the bridge, the vertical displacement response of isolation bridge is larger than non-isolation bridge. Longitudinal displacement response is smaller than non-isolation bridge. When brake at single pier the braking force is uniformly distributed to each pier. So the longitudinal displacement response of deck can be diminished effectively and the force distribution reasonably. The most unfavorable position of the train at the train stop on the bridge when the first pair of wheels go out of the bridge.2 Dynamic coupling responses between vertical and transverse dimension analysis program by composite mode method had been written by MATLAB. The vertical and transverse coupling response between train and bridge of bidirectional seismic isolation railway bridge with LRB had been analyzed. The analysis take into account the non-smooth of track and the snake moving of wheels and the vehicle is simulated by 27 DOF model. The influence of isolation period, isolation damp ratio, the initial stiffness and yield load to oscillate response had been studied. The result show that the train passes by the bridge with normal LRB the transverse displacement is large which can not satisfy the safety demand and the displacement of LRB must be restrained.3 The longitudinal and transverse time history response under designed and rare earthquakes of bidirectional seismic isolation bridge had been analyzed by FEM software ANSYS. The result show that the there will be good seismic isolation effect of railway bridge with LRB. Under occasional and design earthquakes the LRB yield and the displacement will be beyond the allowable value, which may cause the damage of track equipments. The large displacement have serious influence to the safety and increase the difficulty and work to the maintenance and economic loss.4 In order to restrain the displacement of bridge deck under occasional and frequency earthquakes, a composite bearing which is combined by LRB and displacement restrainer had been approved here to provide enough initial stiffness and yield strength for isolation bearings. There are totally two types of displacement restrainer:a. Energy dissipation and deform restrain damper: In the design and occousional earthquake the damper and LRB remain elastic state and restrain the deformation effectively. And under rare earthquakes the dampers yield and the composite bearing can isolate the earthquake and dissapate energy. In this section X shape steel plate damper and X shape steel rob had been studied.b. Non-energy dissipation deform restrainer: This restrainer has no plastic stage and when reach elastic limitation the restrainer crack. Under design and occousional earthquake, both of the deform restrainer and LRB remain elastic state. Under rare earthquake the deform restrainer quit and LRB works solely. In this section X shape brittleness steel plate and long neck X shape steel rob had been strudied.5 The material characteristics and mechanical static test is done for the above restrainers. The constitutional relationship and hysteretic relationship had been got by test for FEM simulation. A three spans continuous railway bridge with seismic isolation bearings had been designed. And the shake table test had been taken to the railway bridge, and the test verified the design method is reasonable and the FEM analysis result is right and proved the theory and test demonstration for the practice use of the three composite bearings.