| Composite arch ring reinforcement method has been widely used in masonry arch bridge reinforcement in China due to its advantages of convenient construction,low cost and less traffic impact.In the long-term engineering practice,this technology has been proved to significantly improve the overall performance and bearing capacity of the structure.However,there are few theoretical studies on ultimate bearing capacity of masonry arch bridges after reinforcement.Therefore,it has important theoretical significance and engineering application value to study the stress mechanism and failure theory of composite arch ring reinforced structure.Based on the concept of strain slope and considering the different stress states of reinforced structures,the calculation method of composite arch ring bearing capacity considering secondary stress is studied by combining theoretical analysis,model test and numerical simulation.Firstly,considering the secondary stress characteristics of the reinforced structure,the composite arch ring reinforcement is divided into four stress states according to the direction of the bending moment before and after the reinforcement,namely,positive-positive moment,positive-negative moment,negative-positive moment and negative-negative moment.Based on the concept of strain slope,the calculation method of the bearing capacity of the composite section of the reinforced structure under each stress state is deduced.Secondly,considering the influence of initial stress,eccentricity,thickness of reinforcement layer and material strength of the original structure before reinforcement,seven reinforcement specimens and two unreinforced columns were made according to the principle of controlling variables.Based on the characteristics of the specimens,the bearing capacity test was designed.According to the test process and results,the failure mode and strain distribution of the reinforced structure were studied.Then,the MIDAS FEA finite element software is used to simulate the test process of the specimens,and the stress-strain distribution law of the specimens in the ultimate state is analyzed.The failure mode of the specimens in the test is compared with that of the specimens.The experimental results are verified by theoretical calculation,which proves the reliability of the finite element analysis and theoretical calculation.Thirdly,based on the reliability of finite element analysis,considering the parameters of initial stress,eccentricity,thickness of reinforcement layer and material strength,the parameters are expanded under four stress states,and the results are quantitatively analyzed.The parameters of initial stress,eccentricity,thickness of reinforcement layer and material strength of reinforced structures under different stress states are compared and obtained.The influence on the bearing capacity of the section.Finally,based on the concepts of strip method and iteration method,matlab program is compiled to simplify the calculation theory of secondary bearing capacity of composite section proposed in this paper,and the bearing capacity envelope diagram of composite arch ring considering secondary loading is obtained,which can be used to evaluate the bearing capacity of reinforcement. |
