Experimental and theoretical studies on bond behavior between BFRP bars and HFRC under dynamic load

Due to its excellent crack resistance, hybrid fiber-reinforced concrete (HFRC) has begun to be practically applied in engineering. However, the bond behavior between HFRC and the novel corrosion-resistant fiber-reinforced polymer materials under dynamic loading conditions remains limited. To address this issue, this study fabricated 60 pull-out specimens to investigate the interface between basalt fiber-reinforced polymer (BFRP) bars and concrete. Using an MTS testing system, an in-depth study was conducted on the dynamic bond behavior at the interface between BFRP bars and HFRC under four different loading rates (3E-1 s−1、3E-2 s−1、3E-3 s−1、3E-5 s−1). The research focused on analyzing the impacts of hybrid fiber content and loading rate on the bond performance. By observing the failure modes of specimens under different strain rates and combining with the elastic calculation theory, an improved dynamic bond stress calculation model was deduced, and this model was corrected according to the experimental results. Based on the experimental results, the model was revised. The test results show that the interfacial bond performance between BFRP reinforcement and HFRC is sensitive to the loading rate. When the loading rate ε≤3E−3s-1, it can be observed that the residual stress-strain development during the slip process of the reinforcement in HFRC exhibits a triangular function shape fluctuation, with its fluctuation period related to the rib spacing. At this time, the failure mode is characterized by the interfacial bond failure between the surface layer of the reinforcement and HFRC. However, when ε≥3E−3s-1, the development of residual stress is not significant, and the reinforcement rapidly detaches from HFRC, with the failure mode shifting to the destruction caused by the compression of concrete on the resin surface of the reinforcement.