Flexural behavior of CFST members with an innovative punched shear connection: proof of concept

This paper investigates the flexural behavior of concrete-filled steel tube (CFST) members incorporating a patented shear connection system (EP2305911B1). The study combines experimental bending tests, simplified theoretical analysis, and digital image correlation (DIC). It aims to provide insights into the effects of the punched shear connection on flexural rigidity and moment capacity. A total of six specimens, including both conventional flat-interface CFST beams and those with the patented interface, were tested. Results indicate that although end slip is reduced, the presence of punched voids decreases the overall stiffness and ultimate bending moment. Local DIC analysis reveals localized strain concentrations around the punched regions. Stiffness and bending moment results were compared with predictions from Eurocode 4, AISC, and CIDECT. Serviceability stiffness is generally overestimated, although Eurocode 4 provides the closest approximation, with /EC4 ratios of 0.99 for flat specimens and 0.85 for those with the punched connection. The ultimate bending moment is predicted with only minor underestimations.