Structural performance of prestressed I-shaped fibre-reinforced UHPC - steel composite beams with puzzle-shaped continuous shear connectors

This study explores the structural behaviour of I-shaped prestressed steel-concrete composite beams that combine a high-strength S460 M/L steel web and Ultra High-Performance Fibre Reinforced Concrete flanges. The design incorporates puzzle-shaped continuous shear connectors and high-strength steel fibres to enhance ductile load transfer between the steel web and the two concrete flanges. As an additional innovation, the concrete tensile flange was prestressed to improve its tensile capacity and delay crack formation. To assess the structural performance of such novel composite beams, a series of large-scale bending tests was conducted, utilizing Digital Image Correlation for detailed measurement of strain and crack development. The test campaign focused on different reinforcement configurations and two loading scenarios, providing insight into mechanical behaviour and failure modes. The beams had a free span of 5 m, with 90 mm thick concrete flanges and a total section height of 460 mm. The test results demonstrated high ductility with deformation-related ductility factors ranging from 1,86 to 2,3, at load-bearing capacities up to 1300 kN. This research underscores the potential of prestressed Ultra High-Performance Fibre Reinforced Concrete steel composites with continuous shear connectors for use in resilient composite structures and presents a straightforward analytical approach for calculating the Ultimate Limit State of these beams, providing a solid basis for future investigations and applications in the field of advanced composite systems in civil engineering.