CFDST stub columns with galvanized corrugated steel tubes: Concept and axial behaviour

Concrete-filled double skin steel tubular (CFDST) columns with galvanized corrugated steel tubes are a novel type of composite members. Such column consists of a layer of concrete sandwiched between an outer corrugated steel tube and an inner flat or a corrugated steel tube. It is expected to combine the advantages of each component, and have additional advantages in corrosion resistance, local stability, and ductility. In this study, a total of 21 large-scale stub specimens were fabricated to investigate the axial behaviour of the proposed columns. The test results indicated that such columns are feasible and competitive in local stability and ductility. Generally, a larger axial bearing capacity can be obtained by retaining the inner flat steel tube in the proposed CFDST members while better ductility is gained if corrugated steel tubes are used as both inner and outer skins. Strain/stress analysis of the column surfaces indicated that the confinement provided by the thin-walled corrugated steel tubes on the sandwiched concrete was sufficient. The axial bearing capacity resisted by the corrugated steel tubes was negligible due to its unique configuration together with the accompanied local bending effect. Based on the test results, four available design models for predicting the axial bearing capacities of traditional CFDSTs were adopted to assess their applicability for the newly proposed columns with galvanized corrugated steel tubes, with specific design suggestions proposed eventually.