Load transfer between thin steel plates and ultra-high performance concrete through different types of shear connectors

Abstract

The unique compressive and tensile characteristics of ultra-high performance concrete (UHPC) have enabled advancement of non-traditional shear connectors to provide composite action between UHPC and steel elements. The focus of the current technical literature in this area has been mainly on shear connectors that are used for the load transfer between flange plates and UHPC slabs. There remains a knowledge gap in the applicability of conventional and novel types of shear connectors to thin steel plates, such as web or stiffener plates. This knowledge is critical for the advancement of design guides for steel-UHPC composite members with fully embedded steel shapes and design guides for rehabilitation and reinforcement of the web plate of steel girders. This paper presents the experimental evaluation of three simple shear connectors: (1) traditional headed studs, (2) demountable threaded bars secured with nuts and (3) UHPC dowel connectors. The experimental results show that the connection is governed by fracture of the stud or threaded bar shank adjacent to the weld or at the interface between the web plate and the nut, respectively. The UHPC dowel connectors display brittle interface shear failure of the UHPC, followed by ductile pull-out behavior of the steel fibers. For large-diameter UHPC dowels, it was observed that yielding of the steel plate in bearing controls the capacity because of the relatively small thickness of the steel plate. The failure mechanisms, capacity and stiffness values, and strain demands on the embedded steel plates are presented and discussed. These experimental results are expected to broaden the knowledge of shear connectors incorporated into relatively thin plates and embedded in UHPC.