Analysis Of Force And Differnential Settlement Of The Widened Prestressed Concrete Box Girder Bridge

With the rapid development of China’s economy,road traffic has been unable to meet the growing demand,and the reconstruction of the existing highway bridges is not only costly,but also waste of resources.The method of widening the existing highway bridge is a comprehensive reuse of the bridge,and conforms to the national policy of energy saving and emission reduction,which has important practical significance.First of all,research on common prestressed concrete box girder bridge as widening object,by analyzing the widening technology of box girder bridge,and combining with the domestic testing methods at home and abroad,the "three level" evaluation process of box girder bridge widening is established.Secondly,after the bridge widening,the new and old bridges are subjected to common force,and the different splicing methods of the old and new bridges will affect the transverse distribution of load and the transverse distribution law of the internal force of the bridge after widening.Through analysis of box girder bridge widening transverse force calculation method,application of grillage method construction of box girder bridge model after widening,the variation law of shear and bending moment of different beams is put forward.At the same time,the rigid connection method is more conducive to the overall force of the bridge structure,so in the design of the widening way,selecting the old and new bridge superstructure rigid splicing method,more conducive to the safety of the bridge;Finally,on the basis of the old and new typical bridges,by using MIDAS/FEA method,the support model is constructed,and the relationship between the settlement value and stress of continuous beam and simply supported beam is obtained.It is obtained by simply supported bridge internal force analysis,25 m in span simply supported box girder bridge differential settlement value is greater than 5 mm of each beam has a larger internal force,will lead to new and old bridge joint cracking,so when this type of bridge widening settlement difference should be controlled within 5 mm.Compared with simply supported box girder bridge,continuous box girder bridge in the piers in the settlement,joint of new and old bridges have the maximum tensile stress,through comprehensive analysis,bridge in control of the settlement should be compared with continuous girder bridge is more strict.The application of the research results has improved the safety of road and bridge,and provided a theoretical basis for the reconstruction and extension project of road and bridge.