Performance of concrete-filled outer stainless-inner mild steel tube columns under eccentric compression

Abstract

Concrete-filled outer stainless- inner mild steel tube (CFSMST) columns, consisting of outer stainless steel tube, inner mild steel tube, and infilled concrete, exhibit significant potential for widespread application in high-rise buildings and coastal structures due to their remarkable load-bearing capacity and outstanding corrosion resistance. Nevertheless, the mechanical behavior under eccentric compression of CFSMST columns remains unclear, and there is also a pressing need for the formulation of practical design guidelines specific to this type construction. This study conducts an experimental analysis of the mechanical performance of CFSMST columns under eccentric compression. A total of nine columns, including two Concrete-filled outer stainless steel tube (CFSST) columns and seven CFSMST columns, are fabricated and subjected to eccentric loading. The failure modes, ductility, deformation, strain responses, and steel tube confinement effect of the specimens are analyzed. The influences of inner tube wall thickness, concrete strength, and eccentricity are investigated. Test results indicate that the presence of an inner mild steel tube greatly improves the strength and ductility of the CFSST specimens. Theoretical models for predicting the ultimate bearing strength of CFSMST specimens under eccentric loading are proposed. Numerical calculation for tracking the load-mid span lateral deflection curve during the loading process is established by fiber element method (FEM).