Shear connection of reinforcement stiffened cold-formed U-shaped steel and concrete composite beam

[Display omitted] •The Push-out test on a novel cold-formed U-shaped steel–concrete composite beam was conducted.•The influencing factors on the shear connection between slab and web were found.•Ductile slip and sudden fracture failures were observed.•The longitudinal shear capacity calculation method was proposed.•The degree of shear connection calculation method was proposed and verified by experiment. This paper discusses the shear connection of a novel configuration of U-shaped steel and concrete composite beam with a reinforcement strengthening system (RCUCB). In the push-out experiment on 11 specimens, the effects of the following influencing factors were investigated: the diameter of inverted U-shaped reinforcement (IUR), the number of IUR, the width of varus flanges, and the details of reinforcement truss (RTR). Based on the test results, two distinctive failure modes were found: ductile slip for the cases with IUR; and sudden fracture at the slab-web interface (neck) for the cases without IUR. According to the failure mechanisms, a more exact calculation method for the longitudinal shear capacity at the neck between concrete slab and beam web is proposed, which results in good agreement with the test results. On average, the concrete neck, IUR, and RTR contribute respectively 53%, 28%, and 19% of the shear capacity. Lastly, a reliable method for determining the degree of shear connection in RCUCB is proposed and verified using the earlier test results.