Shear behaviour of steel-headed stud connectors in engineered cementitious composite (ECC) bridge deck under positive and negative moments

Abstract

Steel-concrete composite girders are extensively used in long-span bridges because of their high strength-to-weight ratios and ease of construction. However, concrete cracking can weaken the steel-concrete shear connections, particularly when the concrete layer is subjected to tension, such as in continuous bridge decks under negative moments at mid-supports. Replacing brittle concrete with ductile engineered cementitious composites (ECC) offers a promising solution for improving crack control and maintaining effective shear transfer between layers. This study investigates the shear transfer behaviour of steel-headed stud connectors in ECC under positive and negative moments using push-out and inverse push-out tests. A total of 23 H-shaped steel-ECC composite specimens are tested to examine the effects of loading direction, matrix type, reinforcement ratio, stud length and diameter, and ECC layer thickness. The experimental results indicate that the shear-carrying capacity and slipping ability of steel-headed stud connectors in ECC are significantly higher than those in conventional concrete under negative moments. Furthermore, a numerical analysis is conducted to examine the influence of boundary conditions and ECC material properties on the shear performance of studs. The shear transfer mechanism of studs in ECC was elucidated through a refined finite element model. Finally, existing equations for predicting the ultimate stud connection strength in concrete or ECC are evaluated against the test results. This research provides insights into the design of shear connections in steel-ECC composite structures, particularly for applications involving negative moments.