Strongly reinforced composite dowels (SRCD): a new structural solution and new design concept

Abstract Strongly reinforced composite dowels (SRCD) is a new structural solution that enables the creation of new types of steel–concrete hybrid sections in bridges. It was developed in Poland in 2021 to build a new kind of hybrid bridge, in which the webs made of normal concrete are to be only 20 cm thick, which is less than allowed by the current regulations for designing structures with a composite dowels shear connection. The design solution assumes the use of such a high density of bars in the vicinity of steel dowels that brittle mechanisms of concrete failure (pry-out cone) will be eliminated while ensuring such a degree of confinement of the concrete dowel core that the failure mechanism can be classified as close to the currently adopted shear failure mechanism. The target concept of design, the scientific basis of which is presented in this paper, is therefore completely different to the present one. Instead of two criteria for concrete failure in the form of pry-out cone and shear, there will be only one criterion in the form of shear with a reduced confinement effect. It is emphasized that the obtained load-bearing capacity will be significantly greater than calculated from the current pry-out criterion, which always decides when designing a bridge structure. It is noted that under the proposed concept, two separate issues were simultaneously recognized, linked, and solved: the first concerns a narrow concrete web and the hypothetical pry-out cone perpendicular to the surface of the steel web, and the second concerns the pry-out cone from the bottom of the web.