Seismic Performance Evaluation of Exterior RC Beam-Column Connections Retrofitted with Economical Perforated Steel Haunches

The exterior beam-column joint (BCJ) within reinforced concrete (RC) frame structures is acknowledged as a vulnerable component prone to seismic failure. This article proposes a practical and economical strengthening method for exterior BCJ using a perforated steel haunch system. This perforated steel haunch system is designed to mitigate damage in BCJs and improve seismic performance of the structure. Employing finite element modeling (FEM) techniques, the study investigates the impact of perforated steel haunches on BCJ behavior and performance. The investigation involved creating nine distinct models, each representing a BCJ with a steel haunch system. These models included a control model without any perforations and eight variations with different levels of perforation (ranging from 10% to 50%) within the steel haunch system. Furthermore, the study analyzes the influence of perforation shapes on the connection's performance, considering square, circular, hexagonal, and triangular shapes. The findings reveal that employing a steel haunch without perforations significantly increases the load-carrying capacity of a BCJ by about 89%. Additionally, circular or square-shaped perforations, up to 30–35% within the steel haunch, effectively prevent joint failure and promote ductile behavior. These findings hold the potential to advance the design methodology for RC joints subjected to seismic loads, thereby enhancing structural resilience in earthquake-prone regions.