Flexural behavior of FRP-HSC-steel double skin tubular beams under reversed-cyclic loading

This article presents an experimental study on the cyclic behavior of fiber reinforced polymer (FRP)-concrete-steel double skin tubular (DST) cantilever beams, referred to in this article as DSTBs. Four DSTBs constructed of high-strength concrete (HSC) were tested under reversed-cyclic lateral loading. The main parameters under investigation were the size of the inner steel tube, the provision (or absence) of a concrete filling inside the steel tube, and the installation of mechanical connectors in the form of steel rings welded on the inner steel tube. The results indicate that DSTBs exhibit very ductile behavior under reversed-cyclic lateral loading. The results also indicate that the DSTBs with larger inner steel tubes exhibit lower lateral displacement capacities compared to their counterparts with smaller inner steel tubes. It was observed that installation of mechanical connectors on the inner steel tube and concrete-filling the tube both influence the overall behavior and lateral displacement capacity of the DSTBs. Furthermore, the results show that through the use of mechanical connectors the slippage at the interface between the steel tube and surrounding concrete sleeve can be completely eliminated.