Numerical Investigation of Plastic Hinge Length and Lateral Displacement Capacity in Precast Concrete Columns Reinforced with SFCBs

Basalt fiber-reinforced polymer (BFRP) presents several advantages, including a moderate elastic modulus, cost-effectiveness, and a substantial fracture strain. A steel-FRP composite bar (SFCB) is a composite bar consisting of an inner steel bar and outer longitudinal BFRP, and it offers favorable initial modulus, high durability, and controllable post-yield stiffness. This study aims to address the issue associated with poor corrosion resistance, connection defects, and low integrity in traditional precast concrete columns with grouted sleeves (PCC-GSs) by employing bond- and post-yield-controlled precast concrete columns reinforced with SFCBs (PCC-SFs). The 3D finite element analysis (FEA) modeling was validated by comparing the results with those of six PCC-SFs and three precast reinforced concrete (RC) columns obtained from the experiment. The results encompass failure modes, load-displacement responses, strain distributions of SFCBs, and section curvature along the columns. The predicted errors for the peak load of S10B85–1P, S10B85–2P, and S10B85–3P are 6.4%, 0.1%, and 1.9%, with a mean error of 2.8%. The predicted errors for the ultimate deformation of S10B85-3PL and ST10B85–3P are within 20%, with a value of 6.0% and 18.7%. Subsequently, a series of FEA models were developed to analyze the effects of various on the development mechanism of plastic hinge length (PHL) for the PCC-SFs under lateral loading. The parameters included the post-yield stiffness ratio, equal-stiffness reinforcement ratio, axial force ratio, concrete strength, and bond strength. The longest plastic hinge length can reach 1.91D (D is the width of the column). An adjusted prediction model for the equivalent PHL in PCC-SFs was proposed and evaluated following a discussion of existing empirical models. Finally, the study explored the effects of these parameters on the load-displacement response, and the rationality of Priestley's shear-strength degradation model in PCC-SFs was validated. Based on the CEN model, an improved prediction model of the total chord rotation capacity was proposed.