Tests of stainless steel circular tubular stub columns with seawater sea-sand concrete infill

A series of cold-formed austenitic stainless steel (CFASS) circular tubular stub columns infilled with seawater sea-sand concrete (SWSSC) were designed, fabricated and tested. The CFASS circular tubes had 3 different cross-sections with its nominal outer diameter of 60.5, 114.3 and 165.2 mm. The concrete mixes were of strength levels 35 and 70 MPa. Axial compression tests were carried out to study their structural behaviour in terms of load-strain curve, strength, ductility and failure mode. The test results revealed that the use of SWSSC in place of conventional concrete in CFASS tubes has little effect on the structural behaviour. The test results were also compared with predictions by existing design equations in the codes. It was found that the existing design equations are either un-conservative or overly conservative. A new and more accurate design equation for axially loaded concrete-filled stainless steel circular tubular stub columns was proposed.