THE IMPORTANCE OF HOOPS AS SHEAR AND CONFINEMENT REINFORCEMENT IN EXTERIOR BEAM–COLUMN JOINTS

Abstract

This study examines 59 exterior beam–column joint (BCJ) specimens from previous research to evaluate the influence of joint hoops on seismic performance. The analysis indicates that joint hoops become increasingly important as the drift ratio increases. To further validate this outcome, experimental tests are conducted on two specimens, namely A-1-100 (with hoops) and A-1-0 (without hoops). The results show that joint hoops have little influence on joint resistance at lower drift ratios. However, as drift ratio increases, side hoops contribute to shear resistance by controlling crack propagation along a joint’s sides. The influence of the side hoops becomes more noticeable but gradually diminishes due to bond degradation. On the other hand, back hoops primarily provide confinement by restricting joint dilation, particularly at higher drift ratios. As damage accumulates, back hoops play a crucial role in maintaining joint integrity and delaying excessive deformation. The findings indicate that joint hoop detailing in exterior BCJs may be optimized without significantly compromising seismic performance, thus offering potential improvements for both new construction and retrofit design. It also contributes to a deeper understanding of the transition from truss to strut mechanisms as drift ratio increases, providing valuable insights for refining analytical models and supporting performance-based design approaches.