Confined concrete with variable crack angle – part I: analytical model

Abstract

Part I of this paper presents experimental results for confined concrete in the form of stress–strain relationships. It seeks to determine the behaviour of confined concrete incorporating variable crack angle and void strain to verify the model. Part II presents the investigation of shear transfer across a definite plane which must be considered in the formation of the crack opening path. This paper develops a constitutive model for confined concrete with variable crack angle that is able to show improved correlation with the experimental data. In the case of fibre confined concrete, comparisons of experimental results of specimens with two different concrete strengths are made to determine the effects of selected variables including fibre volume fraction. While existing material models do not adequately represent the behaviour of concrete air voids confined by composite wraps, a new material model is proposed here, which attempts to overcome the shortcomings in the existing material models. An existing stress–strain model for confined concrete was modified to incorporate a variable angle of internal slope, where the angle minimises the normal stress on the slip surface. An additional modification was the introduction of strains due to collapse of internal voids.