Confinement of six different concretes in CFST columns having different shapes and slenderness

This paper presents behaviour of normal concrete, ultrahigh-strength concrete, engineered cementitious composite, lightweight concrete, self-consolidating concrete and crumb rubber concrete under confinement. Forty-six circular, square and rectangular concrete-filled steel tube columns with varying slenderness are tested under axial compression. Failure modes, axial load–displacement responses and stress–strain characteristics are analysed as well as concrete confined strengths are determined based on experimental results and existing models. The performance of existing confined strength models is evaluated and modified to accommodate different types of high-performance concretes and column shapes. The modified model improves the prediction of confined concrete strength with a mean predicted-to-experimental ratio of 1.05 as shape and concrete type factors are introduced.