Intermediate crack (IC) debonding failure is one of the common bending failure forms of fiber-reinforced polymer (FRP)-strengthened reinforced concrete (RC) beams. In this paper, a new prediction model for IC debonding in FRP-strengthened RC beams is proposed based on fracture mechanics and cohesive zone model (CZM), which takes into account the coupling effect of many parameters and has the advantages of high precision and simple expression. The nonlinear behavior of FRP-strengthened RC beams and the influence of flexural cracks are reasonably considered in this model, whereas all existing analytical models based on the CZM neglect this effects. To verify the accuracy of this model, we established a database containing 248 test data from the existing literature. By comparing the differences between the predicted and experimental results, we analyzed the causes of the error and established a semiempirical model. To test the reliability of the model, it is evaluated using the database constructed in this paper together with four representative strength models. The results show that the semiempirical model has a high accuracy.

The improved high-performance polymer cement mortar (PCM) and glass fiber reinforced plastic (GFRP) system reinforcement was used in the research to strengthen and repair the masonry structure, so as to improve its bond stress, anchoring force, and integral performance without changing the original structure and further study the shear performance of masonry structure strengthened by the combination of the two. The optimum ratio of improved high-performance PCM was determined by analyzing the bend-press ratio of PCM test block. Improved high-performance PCM and GFRP were combined to strengthen the damaged masonry wall, and a five-piece masonry wall composed of “improved high-performance PCM+ with or without GFRP+ different original wall failure modes before reinforcement” was designed. Through diagonal loading shear test, the shear strength, vertical displacement, horizontal relative displacement, and failure models of masonry walls were obtained, and the effects of five different reinforcement methods and different materials on shear strength, stiffness, ductility, and failure modes of masonry walls were studied. The results show that compared with the unreinforced original wall, the shear strength of the masonry wall reinforced with the improved O4PCM is 43.5% higher, and its stiffness is also greatly improved, but the failure mode is still brittle failure; the shear strength of masonry walls strengthened by O4PCM and GFRP is 6.5% higher than that of masonry walls strengthened by O4PCM alone, and the stiffness is also increased. Its failure mode changes from brittle failure to ductile failure; with a failure mode of ductile failure, the shear strength of masonry walls strengthened by P4PCM and GFRP and that strengthened by P6PCM and GFRP are 4.8% and 12.7% higher than that strengthened by O4PCM and GFRP, respectively, and the stiffness is also increased compared with that strengthened by O4PCM and GFRP. After experimental comparison, it is the best scheme to strengthen masonry wall with improved P6PCM and GFRP.