Experiments and calculation methods on the tensile capacity of a single blind bolt anchored in a circular CFST section

Abstract

Composite tubular joints that connect the steel brace and circular concrete-filled steel tubular (CFST) chords are crucial for the performance of entire composite truss structures. While welding is traditionally used for these connections, bolted connections offer an alternative in challenging environments where on-site welding is not feasible. The emergence of blind bolts provides an innovative solution for bolted CFST joints by offering bolted fastening without needing access to the inner surface of a closed section. This paper focuses on the tensile performance of a single blind bolt anchored in a circular CFST section. Experiments are conducted on three different configurations of blind bolts: non-anchored blind bolt with washer, anchored blind bolt without washer, and anchored blind bolt with washer. Based on the tests, the failure mode, the ultimate capacity, and the stiffness of the CFST-blind bolt specimens are investigated. The research findings show that the stiffness and ultimate capacity of the specimen are highly influenced by the bolt diameter, concrete strength, and effective embedment length, as well as the configuration of the blind bolt. And the effective embedment length has the most significant effect on the bearing capacity of the specimen. For every 30 mm increase in bolt effective embedment length, the bearing capacity of the specimen increases by at least 25 %. Finally, practical calculation methods are proposed to determine the ultimate capacity of CFST-blind bolt joints with various configurations under tensile action. The proposed calculation methods demonstrate high accuracy, as evidenced by the good agreement between the calculated values and experimental results.