Seismic performance of TFOSBs bolted endplate connection to CFSST with repaired threaded holes

Abstract

This paper evaluates the seismic behavior of short thread-fixed one-sided bolts (TFOSBs) bolted connection of an I-section beam to concrete-filled square steel tube (CFSST) with repaired threaded holes by enlarging threaded holes through cyclic tests. The parameters investigated were endplate thickness, inner stiffener type, thread anchored length and bolt installation sequence. The test results are presented in terms of strength, rigidity, ductility and energy dissipation capacity. Based on the experimental results: 1) the failure modes of the connections with repaired threaded holes by enlarging threaded holes were similar to the failure modes of the connections having intact hole threads; 2) the connections with repaired threaded holes exhibited 1.8% ∼ 23.8% higher ductility and 3.9% ∼ 46.6% higher energy dissipation capacity compared with the connections having intact hole threads, and the ultimate bearing capacity of those two types of joints were comparable; and 3) the bolt installation sequence has a negligible influence on the failure modes and seismic behavior of connections with repaired threaded holes. In addition, the existing calculation methods of yield moment capacity for TFOSBs bolted endplate connections under various failure modes were still suitable for connections with repaired threaded holes, and the theoretical values and test results were well-matched with errors no greater than 15%.