BEHAVIOR OF HYBRID STEEL-FRP REINFORCED CONCRETE BEAM-COLUMN JOINTS UNDER CYCLIC LOADING: A FINITE ELEMENT ANALYSIS

FRP materials have attracted growing interest within the field of structural engineering, primarily owing to their advantageous characteristics such as lightweight composition, resistance to corrosion, and impressive strength properties. This research endeavor focuses on investigating the behavior of beam-column joints that are reinforced with Fiber Reinforced Polymer (FRP) bars under cyclic loading conditions. These joints share identical specimen geometry, material properties, and testing setups; however, they vary in the extent to which steel bars in the beams are replaced with GFRP and AFRP bars. The alteration in the GFRP or AFRP-to-steel bars ratio ranges from 0% (representing the reference specimen) to 25%, 50%, 75%, and 100%. This comparative analysis is also conducted to assess and contrast the performance of GFRP and AFRP. The primary test outputs encompass the examination of crack propagation patterns and the hysteresis curves illustrating the crack propagation and relationship between forces - displacement. Furthermore, several seismic parameters, including displacement ductility, absorbed energy, and stiffness, will be comprehensively compared and discussed to provide insights into the behavior and potential advantages of those FRP-reinforced beam-column joints in seismic scenario. The results revealed that the type and percentage of FRP reinforcement significantly influenced the cyclic response of the beam–column joints. The hybrid AFRP-steel and GFRP-steel reinforced specimens with 25% and 50% FRP replacement ratios exhibited improved cyclic performance, stable hysteresis behavior, enhanced ductility, and higher energy dissipation capacity compared to specimens with higher FRP content. A comparison between the two FRP types indicated that AFRP-reinforced joints generally demonstrated better seismic performance than GFRP-reinforced joints due to the superior toughness and deformation capacity of aramid fibers. AFRP specimens exhibited wider hysteresis loops, slower stiffness degradation, and greater displacement capacity under cyclic loading. In contrast, GFRP-reinforced joints showed relatively lower ductility and energy dissipation, particularly at higher replacement ratios, because of the more brittle behavior of glass fibers. Keywords: Reinforced concrete, Beam-column joints, finite element analysis, Hybrid reinforcement (GFRP and AFRP), Hysteresis response, ABAQUS