The Analysis Of Downwarping Long-span Prestressed Concrete Continuous Rigid Frame Bridge

With the improvement of engineering technology,the performance of the construction material has been continuously strengthened,and the ability of span has become larger and larger,prestressed concrete beam bridge has been more and more widely used.However,from the existing prestressed concrete beam bridge has been built for the observation,the bridge structure itself appears the disease that can not be ignored,the most obvious characteristic of the disease is that the beam down warp is too large and it appear some cracks.These diseases not only threat to the comfort and safety of driving,but also affect the normal service life of the bridge.Due to a large number of long-span prestressed concrete Rigid Frame Bridge is under building in our country,It is imperative in the project that studying the principle of deflection variation establishing a exact guidance and using a mature engineering technology.The main contents of this paper are as follows:(1)Introducing the general development of long-span prestressed concrete Bridge,pointing out some problems and giving some examples of bridge diseases during the operation of prestressed concrete Rigid Frame Bridge.(2)Expounding the influence factors and the calculation method for the principle of shrinkage and creep of concrete;Introducing the main factors that influence the loss of prestress and the influence of the bridge deflection.(3)Based on the maoertan bridge,deeply studing the factors which lead to the problem of long span prestressed concrete Continuous Rigid Frame Bridge,including the following aspects:? Influence of loading age on deflection;?the longitudinal effect of vertical prestress loss of bridge deflection;?The influence of unbalanced load on the cantilever state;?influence on bridge deflection and uneven settlement of the pier foundation.(4)Introducing the application of precamber method in construction control,comparing and analyzing the calculation method of different camber,choosing the most reasonable linear camber curve,Taking the Maoertan Bridge as an example,calculating the Maoertan camber,and then calculating the elevation of formwork construction.Briefly introducing the basic principle of constant load zero moment theory and Re-configurating the roof beam by the principle of the bending moment of the box girder with prestressed moment,Then the internal force,stress,deflection and internal force of the bridge structure are compared and analyzed,which verifies the feasibility of the method of zero bending moment in the control prestressed concrete Rigid Frame Bridge.Considering the long-term creep and live load,the deflection after 10 years of creep is compared and analyzed,and the feasibility of the zero moment method in the process of controlling the deflection of prestressed concrete Rigid Frame Bridge is verified.(5)The relationship between the deflection and the deflection of the floor slab is studied quantitatively:By the deflection of the bridge under the condition of changing the amount of the bottom plate and the state of the bridge under the condition of 5 years of creep is studied;In order to find out the optimum deflection of the prestressed beam in the bottom slab,the deflection of the main bridge and the change of stress are observed;Based on the analysis of the relationship between the post tensioning time and the mid span deflection,the deflection of midspan deflection is observed by changing the amount of steel beam on the basis of the optimal beam position...