Research On Mechanical Behavior Of Widened Box Girder Bridge Superstructure

With the rapid development of urbanization in China,the demand for road capacity is becoming higher and higher.It is urgent to improve the quality of existing roads and widen existing Bridges by joining them together.Bridge spreader can not only improve the carrying capacity and capacity of the original bridge,but also save money and land compared with the new bridge.The large box type section has high rigidity and good overall shape,and it has better effect than hollow slab and T type section in improving the bearing capacity of the bridge with split width,so it has a wide application prospect.Therefore,it is of great theoretical significance and engineering value to study the mechanical behavior of split beam bridge.Based on the rapid reconstruction project of xiangfu road(hexi section)in changsha city,the girder lattice model of the whole bridge was established with Midas Civil software.The forces of the box girder bridge under the action of vehicle live load,shrinkage and creep,and foundation settlement were analyzed.The research work of the paper is as follows:1.This paper introduces the development of bridge splicing technology at home and abroad and the research status of splicing wide bridge,summarizes the common splicing methods and splicing structure forms in the field of bridge splicing at present,and analyzes the application scope,advantages and disadvantages of each splicing method.At the same time,combined with the actual situation of the project,it is suggested to choose the most reasonable splicing method that the main girder is connected and the bridge piers are not connected.2.Compared and analyzed the application scope and limitations of the four calculation methods of deviated load coefficient commonly used in the field of bridge design,selected girder lattice method to establish the finite element model of split width bridge,and calculated the stress deviated load coefficient and deflection deviated load coefficient of the new bridge.The results are all smaller than the empirical partial load coefficient,It is suggested that the deflection and stress deflection coefficients of split width bridge should be 1.12 and 1.15 respectively.3.By establishing the finite element model of spang-width bridge,the distribution and variation trend of additional internal forces caused by the difference in foundation settlement of spang-width bridge are analyzed,taking into account the settlement at one end of the foundation and the simultaneous settlement at both ends.The results show that the additional internal forces generated by foundation settlement are mainly vertical bending moment and vertical shear force,and the transverse internal forces are less distributed,and the additional internal forces are mainly borne by the internal beams of the new bridge and the original bridge.The internal force distribution law of main girder structure under different splicing forms is compared and analyzed.4.By establishing the finite element model of split width bridge,the distribution law and change trend of additional internal forces caused by shrinkage and creep difference between the new bridge and the original bridge were analyzed.The results show that the additional internal forces caused by concrete shrinkage are mainly distributed in the longitudinal and transverse directions.The additional internal force caused by concrete creep is mainly distributed in the longitudinal and vertical directions of the bridge,and the additional internal force is mainly borne by the inner girder of the new bridge and the original bridge.It is suggested that the best splicing time is 6 months after the completion of the new bridge.