An improved plastic hinge relocation technique for RC beam–column joints: experimental and numerical investigations

Abstract

Although some of the previous plastic hinge relocation (PHR) techniques contribute to enhancing the seismic performance of beam–column joints, they suffer from a serious limitation regarding the reduction of the shear span and related failure mode. This has not been clearly addressed in the literature. So, the present study first examines the challenges of using the classic 90° hooked bar (CHB) method as a representative of other similar techniques such as U-shaped, straight, and headed bar methods. To address the challenges of relocating the plastic hinge (PH), an improved PHR technique is then introduced and studied experimentally and numerically. To do this, four large-scale self-consolidating exterior RC beam–column joints (BCJs) were tested under lateral cyclic loading up to 8% drift ratio, simulating severe earthquakes. The test specimens were comprised of a seismically designed BCJ (without PHR) and three BCJs with two different PHR techniques including (1) the CHB method and (2) the improved technique which was a combination of the CHB method with crossed inclined bars (60° and 30°) in the relocated PH. According to the test results, the use of the CHB method alone led to a significant degradation in the ductility and drift capacity due to sliding shear failure, while the improved technique effectively controlled sliding shear deformations and enhanced the ductility, energy dissipation, and load-carrying capacity. It also reduced the damage severity and prevented the crushing of the core concrete at the PH zone. Finally, some design recommendations are presented based on numerical analysis results.