Structural Behaviour of FRP-ECC-HSC Composite Stub Columns

Abstract

In this study, a novel composite column design has been proposed and experimentally examined, comprising an external fibre reinforced polymer (FRP) tube, an inner engineered cementitious composite (ECC) ring, and a central high strength concrete (HSC) core. Traditional FRP-confined HSC columns are prone to premature failure due to the brittleness of the HSC, leading to localised cracks. To address this issue, the ECC ring, known for its superior tensile and cracking behaviour, is utilized to transfer hoop stress and strain from the HSC core to the FRP tube in the new FRP-ECC-HSC composite column design. Axial compression tests were conducted on stub columns with varying HSC core strengths and ECC ring thicknesses, revealing that the composite columns exhibit improved FRP confining efficiency and a more uniform distribution of hoop strain compared to standard FRP-confined HSC columns. The composite column also demonstrates a noticeable enhancement in ultimate axial strain, resulting in enhanced ductile compressive behaviour. Design equations based on the experimental findings are proposed to estimate the ultimate loading capacity and ultimate axial strain for the FRP-ECC-HSC composite column. Additionally, numerical simulations were developed to analyse the composite column, with finite element models successfully replicating the experimental results.