Component model and design method for tensile behavior of slip-critical blind bolts anchored in concrete-filled steel tubular sections

Abstract

This paper derives a component model to capture the tensile behavior of concrete-anchored slip-critical blind bolt (CASCBB) anchored in concrete-filled steel tubular sections (CFSTS). CASCBB is developed based on a rare blind bolting system which can achieve the same pre-tension as the conventional high strength bolts, i.e. SCBB, good for enhancing the stiffness and seismic performance of joints. Based on the previous experiments and simulation method, a series of parametric studies are performed on the tensile behavior of CASCBB connections. The effect from the parameters is studied in details, revealing the load-carrying mechanism of the connection. The component model mainly including tube face, anchored bolt shank and two concrete struts is derived. Each element has contribution to initial stiffness and yield load. In the second stage, one of the struts fails and the other one is damaged. The ultimate strength can be simplified as the sum of resistance from tube face and diagonal concrete strut. The theoretical model has a good match with finite element analysis (FEA). A simple and practical design method is proposed for determining the configurations and strength of CASCBBs in tubular sections under tensile load. The process of stiffness estimation is also given for such connection.