A novel method for calculating the ultimate bearing capacity of in-service RC arch bridges using sectional constitutive relation

Ultimate bearing capacity is the main basis for evaluating the safety state of in-service reinforced concrete (RC) arch bridges. However, current evaluation methods require a lot of cost to handle the material nonlinearity problem, thereby failing to efficiently addressing such a tough issue. To this end, a novel method for calculating the ultimate bearing capacity of in-service RC arch bridges is proposed. This method accelerates the material nonlinear analysis by the sectional constitutive relation, which avoids the computational intensiveness in conventional methods and may provide a quick solution for structural safety assessment. Firstly, considering the arch axis deviation, temperature change and arch rib damage, the geometric nonlinear differential equation is established, and the real internal force and deformation of the structure are obtained by spline function and Newton–Raphson method. On this basis, the sectional stiffness identification method of in-service arch bridges is developed, in which the identified stiffness is taken as the input parameter. Then, a practical formula of the sectional constitutive relation is proposed to accelerate the material nonlinear analysis based on the fiber model. Finally, the practical formula of the sectional constitutive relation is combined into the geometric nonlinear analysis of arch bridges, by which the double nonlinear analysis of in-service arch RC bridges is fast realized. The effectiveness and superiority of the proposed method is verified experimentally and numerically, and the main factors affecting the service safety of arch bridges are revealed through parameter analysis. The results show that the proposed method can improve the calculation efficiency significantly while maintaining the same accuracy as the traditional method. In numerical validation, the relative calculation error is only 2.08 %, and the total calculation time is only 1/25 of the finite element method.