Behaviour of concrete-filled double-skin thin-walled corrugated steel tubes under axial compression

Concrete-filled double-skin thin-walled corrugated steel tube (CFDCST) is a novel hollow section composite member, developed as an enhancement of conventional hollow reinforced concrete (HRC). In addition to inheriting the advantages of hollow section members, the CFDCST offers benefits due to the confinement and support of outer and inner galvanized corrugated steel tubes (CSTs) such as ease of construction, excellent corrosion resistance, and superior mechanical performance. This paper conducts an experimental study on 20 large-scale specimens (18 CFDCSTs and 2 HRCs), with test variables including specimen types, hollow ratios, and thicknesses of outer and inner CSTs. The experimental results indicated that the CFDCST specimens showed 23.8 %, 48.2 %, and 52.5 % increase in load-bearing capacity, peak strain, and ductility index, respectively, compared with the HRC specimens with identical reinforcements. The nominal hoop stresses of outer CSTs ranged from 0.6 to 0.9 times the nominal yield strengths, meanwhile, the inner CSTs can effectively maintain the section integrity. The failure modes, load-longitudinal strain curves, key indicators, and stress/strain distributions were analyzed carefully. Eventually, the applicability of four existing typical load-bearing capacity calculation models for the novel CFDCST members was examined, with the proposal of relevant design recommendations.