Finite Element Simulation of Socket-type Connection for Square Steel Tube Confined Recycled Concrete Columns

To address the challenges associated with on-site welding quality control in steel tube-confined recycled concrete beam-column joints, this study proposes a novel welded-free socket connection for square steel tube-confined recycled concrete columns. The overall performance of this joint is primarily governed by the mechanical behavior of the socket connection. Based on prior experimental results, a finite element model was developed to systematically simulate the structural performance of the socket connection, with a particular focus on evaluating the influence of three connection configurations: reinforced anchorage type, perforated type, and slotted type. The results demonstrate that the established finite element model accurately reproduces the failure modes and load-displacement responses of the connections, with an average error in ultimate load prediction of 5.75%. Among the three configurations, the reinforced anchorage type exhibits the best overall performance, characterized by high load-carrying capacity, excellent ductility, and a distinct yield plateau when larger-diameter anchor bars are employed. The perforated type follows, demonstrating significant concrete dowel action, with the group effect in double-hole connections resulting in superior capacity compared to single-hole arrangements. The slotted type performs the least effectively, failing in a markedly brittle manner. It is concluded that the proposed welded-free socket connection holds considerable promise for engineering applications, particularly in prefabricated structures requiring high construction quality and joint ductility. The reinforced anchorage type or multi-perforated configurations should be prioritized in design, with full utilization of the group effect of concrete dowel action to enhance structural performance.