Internal Force Optimization And Long-term Stress Analysis Of Arch Of Long-span Reinforced Concrete Arch Bridge

The main arch ring is the main load-bearing structure of a long-span reinforced concrete arch bridge,the main arch ring directly affects the stress state of the arch ring,and then affects the bearing capacity and durability of the arch bridge.In the long-term service stage of reinforced concrete arch bridge,due to the influence of concrete shrinkage,creep and temperature change,the concrete stress of arch section cannot be ignored,and accurately predict the stress behavior.it is of great significance to the safety and durability of long-span reinforced concrete arch bridge.Based on Niuluhe Bridge,a long-span reinforced concrete arch bridge with a net span of 195m this paper studies the following aspects by using finite element software BRanalysis and Midas/civil:(1)several optimization calculation methods of common arch axis and reasonable arch axis are introduced,the suitable arch load forms of different arch axes are analyzed,and the defects of existing arch axis optimization calculation methods are briefly discussed.(2)based on the iterative calculation principle,taking the minimum internal force of the arch ring moment after the completion of the bridge as the optimization objective,a "zero moment difference method" for arch axis optimization is derived.The optimization results of the arch ring internal force are compared with the cubic spline interpolation optimization scheme and the original design scheme.The analysis results show that the maximum bending moment of the optimized arch ring is more than 30%lower than that of the cubic spline interpolation optimization scheme and the original design scheme,and the distribution of arch ring bending moment is more uniform.(3)in order to minimize the sum of the square moment of the control section of the arch ring after the completion of the bridge,the layout of the arch column and transverse wall of the long-span reinforced concrete arch bridge is optimized by using MATLAB programming language and its built-in function fmincon,to solve the constrained optimization problem.After optimization,the bending moment of the arch ring decreases obviously,and the optimization effect of the internal force of the bending moment in the arch foot area is the most obvious.(4)based on the optimization results of arch axis and arch building,the models of construction stage and bridge completion stage are established,the arch ring section stress of the optimization scheme in the construction stage is analyzed and compared,and the stability of each construction stage and bridge completion stage of the arch bridge is checked at the same time.The feasibility of the optimization scheme is proved.(5)based on CEB-FIP(1990)shrinkage and creep model,the effects of common steel bar and different environmental humidity on the shrinkage and creep stress of arch ring are quantitatively analyzed during the long-term use of arch ring.(6)the influence of temperature change on shrinkage and creep is analyzed,and based on this,the coupling effect of temperature and shrinkage and creep on the long-term stress behavior of arch ring of long-span reinforced concrete arch bridge is analyzed.The results show that the long-term stress of arch ring control section shows a downward trend,and the section stress fluctuates up and down in the process.