Tensile behaviour of anchored blind bolts in concrete filled square hollow sections

In this paper, the tensile behaviour of a new type of blind bolt, the anchored blind bolt, has been studied. This type of bolt consists of a conventional blind bolt with a headed stud extension that anchors it into the infill concrete. It has been developed for use in moment-resisting connections between I-beams and concrete-filled hollow section columns. The behaviour of these connections is highly dependent on the tensile behaviour of the anchored blind bolts. Hence, the fundamental mechanics of this behaviour has been studied here, both experimentally and in simulations using FE models. The complex interactions between the headed stud anchorage, the concrete infill, and the steel tube have been examined in detail. The experimental and numerical findings were used to understand the influence of important parameters in the tensile behaviour of the anchored blind bolts. It was found that the location of the bolt with respect to the side walls of the tube had a substantial influence on the behaviour of the anchored blind bolts. All the bolts located close to the side walls of the square hollow sections reached the ultimate tensile capacity of the equivalent structural bolts. This was due to the development of a concrete strut which transferred the load to the corner of the steel section. The bolt diameter also had a significant influence on the stiffness and strength of the anchored blind bolts.