Seismic Pounding Analysis Of Curved Continuous Girder Bridge

Bridge is the pivotal project of the transportation network. And curved continuous girder bridge can fit the restrictions of space and bridge alignment so well that it is used widely in the highway’s small and medium-sized bridge, interchange project of city road, and the approach bridges of the large bridge across a river. However, because of its irregularity, the curve bridge is seismic vulnerable. When confronted with the earthquake, it will not only cause huge economic losses, but also has difficulty in post-earthquake restoration. So the seismic problems of curve bridge has been highly valued in the academia and engineering field. The damage of bridges in all previous earthquake indicated that the adjacent structures’ collision is the main cause of structural damage. And curve bridge are more likely to cause a collision of adjacent components, because the adjacent components have a big difference on dynamic characteristics due to the surface curvature of the structure and the different hight of piers. In Wenchuan earthquake in 2008, there are a lot of bridges damage due to the collision, and the curved bridges are particularly striking. Therefore, this paper researches on the collision response of curved bridges under strong earthquake, in order to understand the collision mechanism of curve bridge and to provide some references for the earthquake resistance design of curve bridge. The main content of this paper is as follows:(1) The research of bridge collision has been summarized and discussed, including the theoretical analysis, test, analysis model, and the analysis method of bridge seismic and collision response. This paper made a comparison of the three simulation methods of bridge seismic collision: the recovery coefficient method, the contact element method and three-dimensional contact friction element method. And the third was selected to analyze the collision response of curved bridge in order to take its uneven collision into account.(2) The analysis model came from the practical engineering, a double column pier bridge, which is used commonly in the southwest mountainous regions. And the three-dimensional finite model was built in ABAQUS. In order to simulate the collision response and guarantee the feasibility of the calculation, the multi-scale method is adopted to divide grid. While the collision parts was established by detailed finite element, other parts used a larger mesh size. The three-dimensional contact analysis model could consider the uneven collision between adjacent components on the basis of penalty function method and the contact search algorithm.(3) The collision response of curved bridge could be obtained through the nonlinear dynamic time history analysis. The results indicated that the curved bridge is easy to collide under the strong earthquake. The great collision force produced by collisions leads to the compression and tensile damage of concrete. The collision effect significantly increases the radial displacement of the main girder, and has obvious influence on the displacement of pier top and pier bottom torque. As a result, the damage of bridge piers gets more serious. Therefore, the influence of the collision should be considered in the seismic design of curved bridge. And efficient measures should be adopted to reduce the collision response.(4) Many factors having influence on the collision response were discussed in the paper, such as the curvature radius, the expansion joint space, the height of piers and the input mode of earthquake ground motion. Research suggests that the small-radius bridges are more vulnerable to the effects of torsion eccentric. While the straight-line bridge usually has a point-to-point frontal crash in the expansion joints, the curved bridge has a local collision in general. The expansion joint space between adjacent structures has a obvious effects on collision. The smaller the expansion joint space is, the more collision occurs. On the contrary, when the expansion joints size increases, the number of collisions decreases, but the collision force increased. The higher the bridge pier is, the greater the collision force is. The collision force with piers in different hights is greater than that of piers in same hight. The input angle of the ground motion has a obvious influence on the collision response. The bigger the angle between the input direction and the direction of expansion joints is, the easier the collision occurs, and the greater the collision force is. Different ground motion has significant difference to the collision response. And collisional stress of bi-directional ground motion input is greater than one-way input.