Seismic Performance Analysis Of Skewed Bridges After Widening

The increase in transportation volume has shortened the adaptation period of highway transportation constructed at the end of the last century in China,and the demand for highway reconstruction and expansion has increased year by year.Bridge widening is the control project for the reconstruction and expansion of expressways.It is an inevitable requirement for the implementation of the project to ensure that the required functions and service life after the bridge is widened.The skewed bridges appearing in a large number of highways have complex interaction mechanisms under the dynamic action of the new and old structures.The reasonable widening method is adopted to ensure that the seismic performance of the skew bridges meets the fortification requirements after widening,which has important engineering practical value.In this paper,a four-span oblique prestressed concrete continuous girder bridge in the Shanxi Province of Lichang Expressway is taken as an example to analyze the seismic performance of the crossover bridge before and after widening.For the bridge and the bridges with three widening schemes,four finite element models were established using the large-scale general finite element software ANSYS.The XTACT software was used to calculate the section characteristic parameters of the potential plastic hinge position under the self-weight of the pier.It is then input into the combined plastic pier model of the combined pier.Under the action of pile-soil,the El Centro south-north and east-west seismic waves after amplitude modulation were selected,and the elastoplastic seismic response analysis of the four models was carried out using the input mode of uniform excitation.The occurrence position,appearance time,number of occurrences and number of damages of the plastic piers of the piers under various seismic conditions are compared.The maximum displacement of the main girder and the maximum displacement of the girder under the peak acceleration of each working condition are compared.The maximum relative displacement of the main beam and the cover beam and the maximum displacement of the top of the pier.The results show that: the predetermined three widening schemes,the damage degree of the piers meets the requirements of the eight-level seismic fortification;the first condition is the more unfavorable working condition of the elastoplastic capacity of the pier,and the original bridge model is destroyed under the seismic wave of 0.4g peak acceleration.Except for the original bridge model with the peak acceleration of 0.4g and the full-connection model(rigid connection of the main beam and the connection of the cover beam),the other models have plastic piercing damage of the pier under the peak acceleration of 0.3g;the three widening models are in each The maximum displacement of the main beam,the maximum displacement of the cover beam,the maximum relative displacement of the main beam and the cover beam,and the maximum displacement of the pier top are basically smaller than the corresponding displacements of the original bridge model.The four displacement indicators of the full connection model are in the four types.The smallest model in the model(the main beam rigid connection,the cover beam is not connected)is not much different from the earthquake;the elastoplastic deformation ability of the pier and the comparison of the above four displacement indicators are concluded: the full-seismic model has the most seismic performance.Well,the upper model is not much different,and the articulated model is the weakest.It is recommended to choose the widening method of the rigid connection of the main beam,and the new and old cover beams can be connected or not connected.At the same time,the pile bottom beam should be added,and the new pier longitudinal reinforcement and stirrup reinforcement ratio should be increased to improve the ductility of the pier.The research results of this paper can provide reference for similar bridge widening projects.