Research On The Ultimate Load-Carrying Capacity Of Stone Arch Bridge Reinforced By Concrete Arch-lifted Method

A large number of stone arch bridges are in active service in our country, but many ofthem need reinforcement. The reinforcement by using reinforced concrete arch-lifted forstone arch bridge has been widely used for convenience and lower costs.In the current code, the arch ring is transformed into an equivalent compression bar,the length of which is obtained according to the stability theory. The ultimate state is notbased on the arch structure but the member. In addition, the load-carrying capacitycalculation formula for enlarging section area reinforcement method in the codeSpecifications for Strengthening Design of Highway Bride（JTG/T J22-2008） is onlysuitable for the reinforced concrete members, and not for the composite arch ring withreinforced concrete and stone using concrete arch-lifted reinforced method. Furthermore,the research on the load-carrying capacity of composite arch ring is based on thecross-section intensity analysis of composite arch ring. For the composite arch ring, nopractical simplified algorithms of ultimate load-carrying capacity have formed. To solvethe practical problem，some researches have been done in this paper. The main tasksinclude the following：（1）The calculation method of the ultimate load-carrying capacity for stone archbridges and the reinforcement technology of stone arch bridge strengthened by reinforcedconcrete arch have been summarized.（2）Using the finite element program ABAQUS, the finite element models of thestone arch ring and composite arch ring which can consider unilateral contact-friction andmaterial nonlinear analysis are establishsed. Comparing the obtained numerical resultswith the test results shows that the mechanical behavior of the arch ring can be depictedwell by the finite element model.（3）Analysis of the limit state of stone and composite arch ring have been done basedon the finite element models. Results showed that under the half span distributed load andquarter point load, the failure mode for both stone arch ring and composite arch ring arefour-hinges failure mechanism. The load reaches the53.1%~64.5%of ultimate load when the first hinge appears, The load reaches the77.8%~89.8%of ultimate load when thesecond hinge appears. Small load increment (10.2%~22.2%of the ultimate load) may leadto two other hinges.（4）Parameter analysis results of composite arch ring ’s ultimate load-carryingcapacity show that thickness of reinforcement layer and reinforcement ratio are the mainparameter, and concrete strength has a little influence on the ultimate load-carryingcapacity of composite arch ring. The ultimate load-carrying capacity of stone arch ring andcomposite arch ring varies under different forms of load. Only half span uniformlydistributed load and only quarter point load lead to the maximum and the minimumultimate load-carrying capacity respectively.（5）Method of finding the section ultimate bending moment of arch ring by the M-Ninteraction curve and path curve under load is used. Two different kinds of M-N interactioncurves are used for composite arch ring to obtain the section ultimate bending momentaccording to the different directions of the section moment.（6）The calculation formula of the ultimate load-carrying capacity expressed by thesection ultimate bending moment for arch ring under half span uniformly distributed loadand quarter point load is deduced. The simplified algorithm of ultimate load-carryingcapacity for stone and composite arch ring is obtained by solving the section ultimatebending moment. Comparing the simplified algorithm results with finite element results, itshows that the simplified algorithm is accuracy and provides engineering with references.