A comparative study of models for confinement of concrete by circular spirals

Abstract

A number of analytical models have been proposed for predicting the stress-strain curves of spirally confined concrete. In this Paper the analytical models available in the literature for confinement of concrete by circular spirals are studied, and their predictions are compared with experimental results reported in the literature. It is concluded that none of the analytical models could accurately predict the stress-strain curves for the full range of experimental data considered in this study. Most of the models were able to predict the peak strength but failed to predict satisfactorily the associated strain and the stress-strain curves. The stress-strain predictions of some of the models were adequate for low- and medium- strength concretes, but the models demonstrated poor prediction for higher strength (f′c< > 42 MPa) concretes. Some of the models predicted the stress-strain curves better for concrete confined with lower amounts of spiral confinement (ρps > < 0·01) than for concrete confined with higher amounts of spiral confinement (ρps < > 0·01). The predictions of the iterative model of Ahmad and Shah were generally in closest agreement with the experimental results. Since this model utilizes the multiaxial properties of concrete and employs an interaction between the dilation characteristics of the concrete core and the spiral confinement, it appears to be the most suited to the accommodation of parameters influencing the stress-strain response of spirally confined concrete.