Behavior of large-scale hybrid FRP-concrete-steel double-skin tubular beams with shear connectors

Hybrid fiber-reinforced polymer (FRP)-concrete-steel double-skin tubular members (DSTMs) are a new form of hybrid members that consist of an outer tube made of FRP and an inner tube made of steel, with the space between them filled with concrete. The existing studies on hybrid DSTMs have been mainly focused on their use as compression members, with only a very limited number of studies on their use as flexural members [i.e., hybrid double-skin tubular beams (DSTBs)]. This paper presents the first ever experimental study on large-scale hybrid DSTBs with headed shear studs; the effect of an integrated deck is also examined. The main parameter examined in the experimental program was the section configuration. The test results show that both the DSTBs and the DSTB-deck unit possessed a very ductile response, and that the headed shear studs effectively reduced or eliminated slips between the steel tube and the concrete. This paper also presents a theoretical model based on conventional section analysis. The predictions from the theoretical model are in reasonably close agreement with the test results.