Modified damaged plasticity and variable confinement modelling of rectangular CFT columns

Concrete damage plasticity (CDP) model is widely used to represent the constitutive behaviour of confined concrete in finite element analysis of concrete-filled tube (CFT) columns. This model requires a constant dilation angle and a stress-strain base curve of concrete as the main input parameters. However, in the case of rectangular CFT columns, the variation in the level of confinement across the cross-section makes both the dilation angle and stress-strain base curve to be solution-dependent. In this study, a novel algorithm has been developed to estimate the dilation angles and to generate the multiple stress-strain curves of concrete under various confining pressures. A numerical technique has been proposed for the modelling of confined concrete in the modified CDP model through the implementation of a solution dependent field variable (SDFV). The efficacy of the proposed modelling technique has been verified through finite element validation of twenty previously tested reinforced concrete (RC), CFT and reinforced-CFT (RCFT) columns under both concentric and eccentric axial loads. Tension stiffening effect of concrete has also been considered in the modelling of eccentrically loaded CFT columns. The proposed numerical models accurately predicted the load-deformation behaviour of CFT columns with and without confining reinforcement under concentric and eccentric axial monotonic loads. (c) 2020 Elsevier Ltd. All rights reserved.

Automated summary

A novel algorithm has been developed to estimate the dilation angles and multiple stress-strain curves of concrete in rectangular CFT columns, and a numerical technique has been proposed for modelling confined concrete behavior with a solution dependent field variable. The efficacy of the proposed modelling technique has been verified through finite element validation of RC, CFT, and RCFT columns under different loading conditions, accurately predicting the load-deformation behavior of CFT columns.