U-shaped steel–concrete composite girders have gained increasing attention in modern structural applications due to their construction efficiency, favorable rigidity, and high strength-to-weight ratio. The overall composite action of such systems, however, largely depends on the performance of the shear connectors that transfer longitudinal shear forces between the steel U-section and the concrete. Conventional welded angle connectors, though capable of providing high initial stiffness, are prone to brittle tearing at the weld toes and suffer from residual stresses and fabrication challenges. To overcome these limitations, this study presents a proof-of-concept investigation into bolted angle connectors as a ductile and construction-friendly alternative. Seventeen push-out tests and a suite of validated finite-element simulations were conducted to evaluate the effects of geometric, material, and construction parameters on shear transfer, deformation, and resistance. Two distinct failure modes were identified: (i) combined angle plasticity and bolt shear failure (Mode I) and (ii) pure bolt shear failure (Mode II). Specimens with large bolt diameter-to-angle thickness ratios (d/t > 4) developed a dual-hinge mechanism, in which two plastic hinges formed in the bolted and vertical legs. This mechanism embodies the capacity-design principle, enabling sustained rotation, delayed bolt fracture, and gradual post-peak response. In particular, its resulting slip capacity readily satisfied the 6 mm ductility criterion of Eurocode 4, thereby qualifying these connectors as ductile. A power-law regression model was developed to relate the connector shear resistance to geometric and material parameters, and a flange-corrected version was proposed to account for the flange effects of thin-walled U-sections. Both formulations demonstrated good predictive accuracy.
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