A COMPARATIVE-STUDY OF MODELS FOR CONFINEMENT OF CONCRETE BY CIRCULARSPIRALS

A number of analytical models have been proposed for predicting the st ress-strain curves of spirally confined concrete. In this Paper the an alytical models available in the literature for confinement of concret e 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 t his study. Most of the models were able to predict the peak strength b ut failed to predict satisfactorily the associated strain and the stre ss-strain curves. The stress-strain predictions of some of the models were adequate for low- and medium-strength concretes, but the models d emonstrated poor prediction for higher strength (f(c)' > 42 MPa) concr etes. Some of the models predicted the stress-strain curves better for concrete confined with lower amounts of spiral confinement (rho(s) < 0.01) than for concrete confined with higher amounts of spiral confine ment (rho(s) > 0.01). The predictions of the iterative model of Ahmad and Shah were generally in closest agreement with the experimental res ults. 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 s uited to the accommodation of parameters influencing the stress-strain response of spirally confined concrete.