Study On Long-term Performance And Concatenation Of Prestressed Concrete Continuous Girder Bridges

Due to the increase of traffic volume and the reasons of bridge structure design and construction,continuous girder bridges are faced with many problems and challenges: long-term deflection of long-span prestressed concrete continuous box girder bridge and widening of box girder bridges because of traffic growth.Based on the actual projects,this paper analyzes the two problems,including the following aspects:1.In view of the difficulty of transverse splicing of new and old box girders of large cantilever box girder bridge with transverse prestressed tendons,a concatenation designing for prestressed concrete continuous box girder bridge with long cantilever is proposed.The finite element models of the spliced box girder are established;2.Analyses of the stress state of splicing section of rigid box girder bridge under the action of uneven settlement of foundation,temperature gradient,vehicle load and shrinkage and creep are conducted,which lay the foundation of further design.The safety checking calculation for the old bridge structure after splicing is carried out,and the bearing capacity of splicing section is calculated.Through the stress analysis of the splicing section,it is found that the temperature gradient and shrinkage creep have a great influence on the structure.And at the fulcrum position,it is necessary to pay attention to the possible adverse effect of the settlement difference between the new and old bridge foundation.In addition,attention should be also paid to the transverse stress of splicing section caused by local vehicle load;3.Parametric analyses of the factors affecting the stress of the spliced structure are conducted,including numerical values of uneven settlement of foundation,waiting time of concatenation,thickness and material of splicing section.Corresponding measures are put forward to improve stress state of splicing section.The analysis results show that controlling the foundation settlement difference can effectively reduce the lateral stress value at the fulcrum position,prolonging the waiting time of splicing and increasing the fly ash content can reduce the influence of the shrinkage creep stress on the splicing section.Changing the thickness of the splicing section can reduce the influence of the foundation settlement difference,but also reduce the rigidity of the splicing wide structure,which should be carefully decided.4.Summarizes and analyzes the main factors influencing the long-term deflection of long-span prestressed concrete continuous beam bridge through practical investigation and the finite element software modeling,including concrete overweight,prestress loss and the automobile load effect.The comprehensive analysis of the influence of different factors on the long-term deflection is given;5.Combined with some engineering cases and practical bridge design experience,from aspects of design and construction,this paper puts forward some measures to prevent and control long-term deflection of longspan continuous beam bridge from multiple angles.