Study on bond performance of GFRP bars in coal gangue concrete based on energy method

Using coal gangue as coarse aggregate to prepare concrete can alleviate the shortage of natural aggregates and utilize solid waste. The corrosion resistance of GFRP bars can solve the steel corrosion problem in coal gangue concrete, and their bond performance is key to engineering applications. In this paper, 16 groups of 48 center pull-out specimens were designed to study the effects of coal gangue replacement ratio, GFRP bar diameter, concrete strength, and anchorage length on bond performance. ABAQUS was used to establish a finite element model to verify the rationality of the simplified bilinear constitutive model. Based on the energy method, an expression for the distribution of bond stress τ along the anchorage length was derived, followed by a formula for the basic anchorage length, and the influence of key parameters on interfacial shear stress distribution was analyzed. The results show that the simulation results of the simplified bilinear model agree well with the experiments. In the elastic stage, the bond stress τ distribution exhibits the characteristics of concentration at the loading end and exponential decay toward the free end. Anchorage length, bar diameter, coal gangue replacement ratio, and concrete strength significantly affect the interfacial stress distribution, with relative anchorage length and bar diameter being highly sensitive factors influencing the interfacial characteristic coefficient. Under the test parameters of this study, the basic anchorage length is approximately 17.6 to 28.0 times the bar diameter. The research findings improve the theoretical system of interface bond-slip behavior of GFRP bars in coal gangue concrete, providing experimental and theoretical support for its engineering application.