Experimental and theoretical study on shear performance of T-shaped and bulb flat shear connectors in composite structures

This study investigates the mechanical performance and theoretical design methods of T-shaped and bulb flat shear connectors in large-scale steel-concrete composite structures. The full-scale push-out test were conducted, including 9 groups of T-shaped and 6 groups of bulb flat shear connectors. The failure modes, crack development patterns, stress distributions, shear force-relative displacement relationships were analyzed across the specimen groups. Experimental results demonstrate that the shear behavior of T-shaped and reverse bulb flat shear connectors is governed by the crushing of non-reinforced concrete at the web root region under stress concentration, whereas that of normal bulb flat shear connectors is controlled by splitting along crack propagation from the bulb ends. Furthermore, reverse bulb flat shear connectors exhibit significantly enhanced shear performance compared to normal types under identical design conditions. Incorporating the superimposed contribution of compressive concrete adjacent to the flange or bulb, modified design methods applicable to T-shaped and bulb flat shear connectors are proposed based on the elastic foundation beam models for traditional L-shaped shear connectors. Validated against experimental results, these formulas can accurately estimate the shear stiffness and capacity of the two types of connectors.