Seismic performance of TOBs bolted endplate connection to concrete-filled square steel tube with damaged hole threads repaired by using spiral wire inserts

Abstract

Thread-anchored One-side Bolts bolted Endplate Connections to Concrete-Filled Square Steel Tube (TOBEC-CFSSTs) have a great potential in steel structures for its excellent behavior and ease of construction, but the hole threads of the column wall are easily damaged on account of non-standard operations of workers in the installation process. Thereupon, this paper proposes a novel thread repairing method, i.e. Spiral wire inserts, to repair the damaged hole threads, which ensures the safety of TOBEC-CFSSTs. Tests on seven specimens were conducted to investigate the seismic behavior of the hole threads-repaired connections with inner stiffeners under cyclic loading. The experimental parameters contained the inner stiffener type, the thread anchored length, the anchorage detail of bolt and the endplate thickness. The performance of the connections with repaired threaded holes were analyzed and compared in terms of failure modes, strength and rigidity, the ductility and the energy dissipation capacity. It was found that the connections using spiral wire inserts to repair the hole threads can exhibit a comparable mechanical property to that with intact hole thread. Besides, the presence of the epoxy adhesive in bolted endplate connections made the assembly of components more flexible without considering the concrete cast sequence, which revealed that the TOBEC-CFSSTs with repaired threaded holes would present extensive application prospects in prefabricated or built-up modular steel buildings. • Spiral wire inserts were used to repair threaded holes for Thread-fixed One-side bolts (TOBs). • TOBs bolted Endplate Connections under cyclic loads were tested. • Moderate strengthening component can enhance ductility and energy dissipation capacity. • Effects of concrete cast sequence on connection seismic behavior were presented.