Review on blind bolted connections to concrete-filled steel tubes

Development of blind bolting systems offers an alternative solution of jointing steel beams to concrete-filled steel tubular (CFST) columns that only allow one-side access. This paper presents a critical review on recent studies about the blind bolted connections to CFSTs representing the tension zone in a beam-to-column joint. Various types of blind bolts have been proposed to improve their tensile behavior in CFSTs by implementing innovative interlocking mechanisms to tube wall and anchoring techniques in concrete. Experimental and finite element (FE) studies were first reviewed in this paper. Tensile behavior of a single bolt or a group of bolts in CFSTs was investigated by one-side or two-side pullout test. Its performance depended on a wide range of parameters, such as bolt type, bolt size, bolt grade, bolt layout, tube size, tube yield strength, concrete strength and embedment length. In FE simulations, modeling of concrete using concrete damage plasticity model was reviewed in detail to provide insights for an accurate FE analysis. Theoretical models for the tensile behavior of blind bolted connections to CFSTs were then reviewed. Strength and stiffness of a connection are mainly contributed by the tube face wall bearing effect, the anchorage in concrete and the elongation of bolts. Finally, potential research directions for future studies were suggested for blind bolted connections. In general, this jointing technique has a broad prospect to achieve a semi-rigid or even a rigid connection in beam-to-CFST joints.