Hybrid FRP–Concrete–Steel Double-Skin Tubular Columns: Creep Behavior and Compressive Behavior after Sustained Loading

Hybrid fiber-reinforced polymer (FRP)–concrete–steel double-skin tubular columns (DSTCs), which consist of an inner steel and an outer FRP tube, with the space between the two tubes filled with concrete, are a promising form of hybrid columns for structural and durability performance. Extensive research has been conducted on the short-term mechanical behavior of hybrid DSTCs. However, in practice, most columns are subjected to long-term sustained loading; therefore, the creep behavior of these novel columns should be deeply understood before they are widely applied. No research has been conducted on DSTCs under long-term sustained loading, to the best of the authors’ knowledge. This paper reports the first experimental program on the creep behavior of hybrid DSTCs under sustained loading to explore the effects of important parameters, such as the concrete, FRP and steel tube thickness, sustained compressive load ratio, and shear studs, on the creep behavior of the hybrid DSTCs. After the sustained loading, axial compression tests on the hybrid DSTCs were conducted to evaluate the effect of sustained loading on the compressive behavior (e.g., load-carrying capacity) of these columns.