Research On Mid-span Deflection Control Technology Of Long-span Continuous Rigid Frame Bridge

With the rapid development of national road construction,continuous rigid frame bridge has been widely used because of its high stiffness,Large-span rigid-frame bridges with spans between 100 m and 300 m have become more common in recent decades.With the rapid development of national road construction,continuous rigid frame bridge has been widely used because of its high stiffness,However,the stiffness of long span rigid frame bridge decreases in the later operation,and the problem of continuous increase of mid-span deflection begins to highlight.In this paper,the midspan deflection under the influence of segmental joint and prestress is studied by the flexural test of segmental concrete and the analysis of finite element model of bridge.The main contents of this paper are as follows:(1)Development process of pc continuous rigid frame bridge and problems existing in cantilever construction are described.The problem of deflection of long span continuous rigid frame bridge and the research status of segment joint are introduced.(2)The bending deflection law of concrete beam under the influence of joint is studied by designing section joint bending test.The influence of the construction joint on the bending deflection of the beam section is simulated by using the section pouring specimen.The influence of interface treatment,section reinforcement and prestressing on the bending resistance of joints is considered.The influence law of each factor is analyzed to provide the basis for the bending resistance of bridge segment joint.The results show that: Chiseling makes the joint concrete bonding ability to be effectively improved;The influence of the spacing between the bars on bending performance is nonlinear,With the increase of reinforcement spacing,the improvement of bending resistance of segmental concrete gradually weakens;Increasing the size of prestressing force can effectively delay the cracking time of beam.(3)The main span 200 m continuous rigid frame bridge——Pinglu Canal bridge are studied.The full bridge model is established by finite element software,and the influence of segmental joint and prestress loss of long steel bundle on the mid-down deflection of long span continuous rigid frame bridge is studied.The results show that: The prestress loss of roof steel bundle has more influence on the mid-span deflection than that of bottom steel bundle;The effect of bridge section joint disposal on midspan deflection is nonlinear,Poor initial disposal will lead to accelerated deflection of bridge span.(4)Based on findings,Combined with physical engineering,Control of mid-span deflection of long span continuous rigid frame bridge,proposed measures from design,construction and operation,and track and observe the deflection of the real bridge.