Pull-out behaviour of blind bolts from concrete-filled tubes

The use of concrete-filled steel circular hollow sections as columns is becoming more popular because of their superior capacity, good ductility and large energy absorption capacity. The utilisation of blind bolts, which can be installed from the outside of the column, is possible and has been the subject of considerable research. Results from pull-out testing of blind bolts and the headed anchor blind bolt, which is a modification of the original blind bolt, are reported in this paper. The tests were performed to establish the behaviour of individual bolts. Results from the research will ultimately be used in the design of moment-resisting connections using these bolts. The effect of varying several parameters such as the tube thickness, bolt diameter and embedment depth were investigated both experimentally and by way of numerical models using finite-element analysis. After achieving a good agreement between the experimental and numerical results, further analysis was implemented to determine the relative contributions of the concrete and tube wall to the pull-out resistance. Parametric studies on concrete strength and embedment depth were also performed.