Experimental investigation on slender concrete-filled double-skin corrugated steel tubes under eccentric compression

Concrete-filled double-skin thin-walled corrugated steel tubes (CFDCSTs) are novel hollow section composite members consisting of outer and inner galvanized corrugated steel tubes (CSTs) with sandwiched reinforced concrete. They have shown great applicability in scenarios such as bridge piers and exposed beam-columns in buildings. While the failure modes, working mechanisms, and load-bearing capacities of short CFDCST members have been studied, their stability performance requires further investigation. Therefore, thirteen large-scale slender CFDCST specimens with effective lengths of 2763 mm and 4263 mm were prepared and tested under eccentric compression in the study. The test variables were the slenderness ratio, eccentricity ratio, hollow ratio, outer CST thickness, and longitudinal reinforcement ratio. The test results indicated that CFDCST specimens failed in a ductile mode and exhibited desirable mechanical performance. As the hollow ratio increased, the bearing capacity decreased while the ductility index increased; the reduction in bearing capacity was less pronounced as the eccentricity ratio and slenderness ratio increased. The thin-walled outer CSTs provided effective confinement, while the thin-walled inner CSTs offered sufficient internal support. Finally, existing design models were modified based on the test results, and their applicability for slender CFDCST members was validated.