Study On The Stiff Skeleton Structure And Stability Of Cantilever Cast Reinforced Concrete Arch Bridge

Reinforced concrete arch bridge has become one of the ideal bridges in mountainous area because of its strong spanning capacity,high bearing capacity,low cost and low maintenance cost.The cantilever casting method has been widely used in the construction of long-span reinforced concrete arch bridges because of its advantages of simple construction,good integrity and no impact on navigation.However,with the increase of the cantilever length of the arch ring,the cable force increases gradually,which not only makes the cable tower bear greater unbalanced horizontal force,but also affects the construction safety,and produces greater concentrated stress at the arch ring buckle point,which increases the difficulty of structural design.This is the key problem to restrict the span development of cantilever pouring construction arch bridge.Solving this problem can achieve a breakthrough in the span of cantilever pouring construction arch bridge.Based on the project of "Structural Design and Dynamic Performance Research of Long-span Cantilever Cast Reinforced Concrete Box Arch Bridge in Mountain Area" supported by Guizhou Science and Technology Fund,this paper takes a bridge as an engineering background and carries out the following research work around the stiff skeleton section near the middle of the span:(1)Collecting and sorting out the development status and construction technology of reinforced concrete arch bridges at home and abroad,analyzing the problems of cantilever casting construction method,and introducing the advantages of cantilever casting method with rigid framework closure.(2)Several different structural forms of rigid skeleton are introduced,their advantages and disadvantages are analyzed,and the influence of different structuralforms of rigid skeleton on the stiffness of arch ring section is calculated.From the angle of construction stability,the section form of web member of rigid skeleton is optimized.(3)The main factors affecting the length of the rigid skeleton section are analyzed.The reasonable length of the rigid skeleton section is determined by studying the displacement of the vault,the equivalent stiffness of the main arch,the maximum cable force during construction and the maximum tension stress of the arch ring,and combining with the completed engineering examples at home and abroad.(4)The construction stability of the cantilever pouring section and the rigid skeleton section of the main arch of the Y bridge is studied,and the stability of the cantilever assembling and integral lifting of the rigid skeleton is compared and analyzed.The influence of two construction schemes,ring-by-ring and whole box-by-ring,on the stability of outsourced concrete in construction stage is studied.