Internal Arch Reinforcement Method For Continuous Rigid Frame Bridge

Prestressed concrete(PC)continuous rigid frame bridge has the advantages of large spanning capacity,comfortable driving and low construction price,which is the preferred bridge across rivers and valleys.During the operation of PC continuous rigid frame bridge,there are often two problems.continuous mid-span deflection and beam cracking,which seriously affect the normal and safe operation of PC continuous rigid frame bridge.At present,the commonly used external prestressing reinforcement method cannot solve the problem of continuous midspan deflection,so the reinforcement method of continuous midspan deflection has important engineering application value.The main research contents of this paper are as follows :⑴ The disease conditions of continuous mid-span deflection of PC continuous rigid frame bridge in China and abroad are summarized,and the main factors affecting the continuous midspan deflection of PC continuous rigid frame bridge are analyzed.The analysis structure shows that the longitudinal prestress loss and beam cracking of PC continuous rigid frame bridge have the greatest influence on the continuous mid-span deflection of main span.⑵ In order to solve the problem of continuous deflection of PC continuous rigid frame bridge,this paper puts forward the internal arch reinforcement method.The basic principle of the internal arch reinforcement method is analyzed from three aspects : the interaction between the reinforcement arch and the anti-arch formed by the deflection of the beam,the pushing effect of the horizontal thrust of the arch,and the combination structure of the arch rib and the box girder.At the same time,the structural form of the internal arch reinforcement is improved,and the corresponding stress stage is divided according to the construction sequence.⑶ Taking the horizontal offset of pier top as the goal,the interaction model between continuous rigid frame bridge and built-in arch is established,and the calculation formula of built-in arch thrust is deduced.In order to facilitate the numerical simulation analysis,the jacking force applied to the built-in arch was simulated by the way of arch rib heating after comparative analysis,and the calculation formula between jacking force and temperature load was deduced.⑷ Taking the actual PC continuous rigid frame bridge as an example,the reinforcement effects of built-in arch reinforcement method and external prestressing reinforcement method are compared.The analysis results show that compared with the external prestressed reinforcement method,the vertical deflection of the bridge strengthened by the built-in arch under vehicle load is 30 % lower than that of the external prestressed reinforcement method.The stress distribution of the original structure can be improved by using the built-in arch reinforcement,and the effect of the top,bottom plate of the beam body and the bottom plate of the mid-span beam section in the L / 4 section of the top of the pier is the best.