Research on Flexural Performance of Reinforced Concrete Beams Strengthened with High-Strength Polyurethane Composites

In order to study the flexural performance of reinforced concrete beams strengthened with high-strength polyurethane composites (HSPUC), the static failure tests of two reinforced concrete beams strengthened by HSPUC reinforcement layer with different strengthening areas at the bottom of the beams and one comparative reinforced concrete beam were carried out, and the failure modes, bearing capacity, crack characteristics, deformation and strain development laws, and interface slip of the test beams were investigated. A refined numerical model was constructed through the finite element program ABAQUS to simulate the flexural performance of reinforced concrete beams strengthened with HSPUC, and the effects of flexural strength and thickness of reinforcement layer on the flexural performance were analyzed. The results showed that the test beams strengthened by HSPUC in non-full length range and full length range of the bottom of the beam experienced debonding failure of the protective layer at the beam end and plastic flexural failure, respectively. Their ultimate bearing capacity increased by 30.4% and 79.4% compared to the unreinforced test beam, respectively. The HSPUC reinforcement method made full use of the high-strength mechanical properties of HSPUC, which could delay the occurrence and development of cracks and therefore effectively inhibit the stiffness decrease caused by crack propagation, significantly improving the flexural stiffness and ultimate bearing capacity of reinforced concrete beams. The reliable bonding strength and good cooperative working performance between the HSPUS layer and the reinforced concrete beam were observed. The mid-span load-deflection curves calculated by the numerical model were in good agreement with the experimental curves, so the numerical model can be used to calculate and analyze the entire flexural process of reinforced concrete beams strengthened with HSPUC.