Behaviour and design of concrete-filled spiral-welded stainless-steel tube short columns under concentric and eccentric axial compression loading

Abstract

Abstract Concrete-filled stainless-steel tube (CFSST) columns, which would be more durable than their mild-steel counterparts, are potentially a more economical method of using stainless-steel for structures. Spiral-welded stainless-steel tubes (SWSSTs) could further increase the cost-effectiveness of CFSST columns. SWSSTs are an alternate and advantageous form of welded tube fabricated by welding a helically bent steel plate. The behaviour of concrete-filled SWSST (CF-SWSST) columns can potentially be different to CFSSTs using other tube types, especially due to larger residual stresses present in SWSSTs. Given this background, twelve self-compacting CF-SWSST short columns with nominal diameter-to-thickness ratios (D/t) equal to 51, 76, 101.5 and 114.5 were tested under axial compression considering eccentricities of 0, 0.15D and 0.4D. The observed failure mode, consisting of flexural local buckling, was equivalent to that reported for non-SWT CFSST columns. The spiral weld did not act detrimentally to the strength. Concrete-filled mild-steel tube design standards provided satisfactory predictions of the experimental capacities for CF-SWSSTs under eccentric loading though they were less conservative when the loading was concentric. The need for separate calibration of design guidelines for CF-SWSST short columns was established since, on average, the actual to predicted capacity ratios were noticeably less than those of non-SWT CFSSTs. Fibre-based section analyses using a confined concrete material model gave better predictions of the eccentric axial capacities than codified methods suggesting greater confinement benefit than considered in the standards are applicable to eccentrically loaded CF-SWSST short columns. The study also confirmed equivalent strength behaviour of CF-SWSST short columns to their mild-steel counterparts though with greater ductility.