Ductility and stiffness of slender confined reinforced high-strength concrete columns under monotonic axial load

Abstract

This paper presents an investigation based on tests results of high-strength concrete (HSC) columns externally confined with post-tensioned steel straps, subjected to monotonic axial load. The parameters of the tests were eccentricity ratio (ei/es = 0, 1), load eccentricity (e = 25 mm, 50 mm), slenderness ratio (λ = 16, 24, 32) and confining volumetric ratio (ρv = 0.09, 0.25, 0.50). This paper is served as a continuation of a previous paper conducted by Ma et al. (2014b), which focuses on the ductility and stiffness analysis. The results show that the confinement of post-tensioned steel straps is beneficial to HSC columns but confining efficiency reduced drastically with the increase of column slenderness. Two ductility models were proposed to predict the ultimate ductility for slender confined HSC columns with the consideration of important parameters. The proposed models are simple and easy to apply but adequately accurate estimation is guaranteed. It is believed that the proposed ductility models can aid structural engineers in the designing a ductile structure especially in the seismic region. The confinement has no significant effect on the flexural stiffness of HSC columns.