Gradually Anchored Prestressed NSM CFRP Strengthened Beams: A Finite Element Method

Gradually anchored prestressed is a technique of gradually lowering and anchoring prestress at both ends of the reinforcement material, which has the advantages of reducing the prestress concentration, delaying the concrete cover separation and improving the bearing capacity. It is widely used in the prestressed carbon fiber reinforced polymer (CFRP) strengthened structures. This paper combines the near-surface-mounted (NSM) technique, firstly, the bond shear stress-slip relationship between CFRP and concrete is obtained from the pull-out experiment, the properties of the spring elements are defined, and the finite element method (FEM) of the pull-out experiment is carried out, which show a good agreement. Then the spring elements are applied to the gradually anchored prestressed beam, and the prestress is applied by adjusting the temperature field, which can simulate the process of gradually anchored well, and the mechanical behavior and bending capacity of the finite element model are in good agreement with the experimental results. Finally, the FEM is used to analyze the law of the influence of the gradient stage length on the bending capacity and deflection of the strengthened beams, which expands the research on the gradually anchored prestressed beams and provides a simple and effective finite element analysis process.