Tests on axial strength of circle CFST stub columns under marine atmosphere in cold region

Abstract

This paper aims to study the compressive behavior of circular concrete-filled steel tubular stub columns under marine atmosphere in cold region. The specimens after salt spray corrosion and freeze-thaw cycles were tested under axial compressive load where steel grade, corrosion rate and freeze-thaw cycles were considered. The experimental phenomena and results are discussed in detail. Current design methods for circular concrete-filled steel tubular stub columns were modified to consider the effect of atmospheric corrosion and freeze-thaw cycles. The results show that the corrosion rate, the cycle number and steel strength have little effect on the failure pattern of circular CFST stub columns, neither on the failure pattern of core concrete. The ultimate strength of specimens is reduced approximately linearly with the increase of corrosion rate and freeze-thaw cycles regardless of steel strength. Strength reductions of the specimens using Q235 steel are smaller than those of the counterparts using Q345 steel. The ultimate displacement and ductility indexes of the specimens are decreased by corrosion rate and freeze-thaw cycle. The enhancement factor φ tends to increase with the increase of test period which indicates that confinement effect contributes to resist the strength reduction due to corrosion and freeze-thaw cycle. Various design standards combined with the reduction factor proposed based on experimental results are adopted to predict the ultimate strength of CFST stub columns under atmospheric corrosion and freeze-thaw cycle.