Study On Problem And Prediction Method Of Long-term Deflection Based On Long-span Continuous Rigid Frame Bridge

Because of long-span continuous rigid frame bridge with the advantages of convenient construction,good structural rigidity,low cost and driving comfort advantages,so it is widely used in bridge construction.But the long span prestressed concrete will be long-term deflection problems later in the process of operation,which limits the further development of long-span continuous rigid frame bridge.The influence factors and mechanism for long-span continuous rigid frame bridge deflection and prediction of long term deflection have not formed a unified concept.Therefore,in order to explore the mechanism of concrete continuous rigid frame bridge long-term deflection of large span prestressed to accurately predict the deflection parameters and deflection,based on the background of a project,the systematic research on the long-term deflection of this paper are anlyzed.The main research contents and conclusions are as follows:(1)The influence factors of long term deflection of long-span concrete continuous rigid frame bridge analysis shows that prestressed reverse bending moment and constant load moment mismatch is caused by the inevitable cause of long-term deformation of concrete bridge,and the main reason is the excessive deflection due to constant load overweight and excessive loss of prestress.The effect of concrete creep,the structure will occur at the same time,long-term deformation,high stress concrete especially work with cracks caused by concrete creep coefficient is larger when the long-term deflection prediction mainly due to excessive and small.According to the different span bridge analysis found that the degree of influence of deck pavement,creep ultimate value and box girder overweight are increased with the increase of the span,span more than 100 m,the ultimate value of concrete creep and deck pavement thickness is the most sensitive factor of two.(2)For large span concrete beam bridge,due to the loss of prestress caused by concrete cracking,and after cracking,the cross section will have a greater loss of prestress,and thus into the long term deflection of the cycle.Compared to the non cracking structure,the cracks will not only cause elastic deformation,and will produce long-term additional deformation.(3)Through the analysis of the factors of deflection,it is indicated that the long-term deflection of long-span concrete beam bridge can meet the superposition principle,so it can be analyzed independently.(4)Forecast for the long-term deflection of long-span continuous rigid frame bridge,this paper presents three methods,each method has its own advantages and disadvantages according to the needs of the engineering and precision of the actual need to use different methods to predict the prediction of long-term deflection of engineering practice,for the project to provide a scientific basis for control long-term deflection.In summary,the results of this paper have been applied to guide the practical engineering,which provides the main basis for the preliminary design and construction drawing design of this type of bridge.