Theoretical modeling for predicting the shear strength of partially-encased composite members with multiple transverse stiffeners

Abstract

Partially encased composite (PEC) members are frequently used as girders in heavily-loaded or long-span structures. In PEC members, the steel web is encased in web concrete between the top and bottom flanges. When PEC members are used in continuous beam spans, the intermediate support area is subjected to significant shear force and negative bending, which is more critical than the span center. As a result, accurate prediction of shear strength is crucial for structural safety in practical design. Unlike traditional concrete or steel beams, PEC beams have multiple shear transfer mechanisms consisting of concrete, steel flanges, axial steel web, and transverse stiffeners (if necessary), and it is essential to investigate the shear contributions of the different mechanisms and how they work together as a composite structure. To solve this problem, this paper presents a novel shear strength model, in which the global shear strength is composed of two main components: the composite truss (steel flanges, web concrete, and transverse stiffeners) and the axial steel web, and these two components are unified by strain compatibility to show the composite action. Then, the proposed model is compared with existing shear equations using 25 existing specimens in the literature, and the results indicate that the proposed model can predict the shear strength of PEC beams with sufficient accuracy. Finally, the paper presents a simplified design method after validating the shear contributions of different anti-shear mechanisms, and the simplified method can facilitate practical design in engineering practices.