Review on research on concrete beam reinforced with HB-FRP [HB-FRP加固混凝土梁研究综述]

To summarize the research results of hybrid bonding fibre reinforced plastic (HB-FRP) reinforcement method and promote its broader application in the field of concrete beam repair and reinforcement, the research status of HB-FRP reinforcement method was investigated. The debonding problem of external bonding FRP under external loads and environmental erosion was revealed. The working mechanism of HB-FRP reinforcement in inhibiting debonding after FRP reinforcement was explained. The structural characteristics of HB-FRP reinforcement system and its influence on the interface bonding performance were analyzed. Existing bonding-slip and debonding load models were summarized. The flexural and shear performance of reinforced beam was studied. The shortcomings of existing studies were analyzed, and future research directions and ideas were prospected. Analysis result shows that both external loads and environmental erosion may induce the debonding of FRP. HB-FRP reinforcement combines the chemical bonding, friction and dowel effect to inhibit the FRP debonding effectively. The main difference among several current HB-FRP bond-slip relationships is whether a stable FRP slip occurs when the interfacial bonding strength is reached. The limit debonding load of the bonding interface depends on its bond-slip relationship. HB-FRP reinforcement can be used for the flexural resistance of normal section and the shear resistance of oblique section, and the bearing capacity and reinforcement efficiency of reinforced beam improve significantly. Increasing the FRP amount and the number of steel fasteners can effectively improve the flexural resistance of reinforced beam. The influence of steel fastener spacing on the bearing capacity of reinforced beam and the reinforcement design criteria are still unclear. The crack and external load have significant effects on the debonding load, material utilization rate, and failure mode of reinforced beam. The increase in the shear strength of reinforced beam mainly generated by the shear forces provided by the FRP and concrete, whereas the influence of stirrup is minimal. The increase in the FRP reinforcement amount and the decrease in the strip spacing can significantly improve the shear capacity of reinforced beam. Follow-up studies on the HB-FRP reinforcement design theory should be continued to propose calculation models for bonding characteristics considering the material and structural characteristics and develop a design method for HB-FRP steel fastener spacing based on the interfacial shear force. Furthermore, the optimized flexure and shear resistance design methods and design formulas for HB-FRP reinforced concrete beams should be developed. 2 tabs, 9 figs, 68 refs.