Interaction Analysis Of Widened Bridge Structure

With large development of highway cause, bridge reconstruction tasks are more and more heavy. A great deal of research works about bridge reconstruction had been done in worldwide and some more successful examples had been obtained, but some key techniques are not formed clear guiding opinions. In the paper, based on projects of typical bridges in Xi'an-Tongguan and Xi'an-Tongchuan Freeway, the study of the method about bridge widening , the traffic capacity of bridge widening, the difference of creep and shrinkage between widen bridge and old bridge, the effects of foundation settlement in bridge structure and the method of settlement control are carried out according to the current existing problem in widening and rebuilding projects.Firstly, the widening methods and connection methods of existing bridges are introduced systematically, and their respective advantages and disadvantages are compared analyzed. So the applicability of widening methods and connection methods are discussed systematically. According to the results and the structural characteristics of relying on projects, widening principle are put forward ,which superstructure connection and substructure isolation operates chiefly and both superstructure and substructure isolation plays only a subsidiary role between widening bridge and old bridge. Secondly, the traffic capacity of bridge widening is analyzed by two ways which are the analysis of load transferring rules along the cross bridge and internal forces and deformation. The results show that deflection and internal forces of old bridges' boundary beam under live loading are greatly reduced after widening, and main girder's connection methods are not significantly effected on old bridge's traffic capacity. The differences in shrinkage and creep have significantly effect on new girders, and the differences make widening bridge's transverse deformation, which the impact of the degree is that the higher shrinkage and creep, the further is the distance from support section. By adopting numerical method to analyze shrinkage and creep which are produced by postpone connect time, the results show that the method can effectively improve the influence of differences in shrinkage and creep. Finally, the effects of additional internal forces about main beam and foundation settlement on the widened bridge are researched respectively after foundation settlement when the different ways have been used to broaden bridges. And the allowable deformation of the connect section is given under live load and foundation settlement. In addition, according to calculate foundation settlement, the settlement value of the bridge is given by using different theoretical, which is compared with allowable deformation of superstructure, in order to give the advice of connect method and the method of control the pile foundation settlement's effect.