An empirical model for predicting the mechanical properties of confined concrete

This paper presents an empirical model for the calculation of the main characteristics of concrete confined by means of hoops or spirals. The model included in CEB-FIP Model Code 1990 was initially used as a basis, its validity was checked against experimental results provided by 17 researchers for more than 300 specimens. Since the comparison showed that the model fails to predict accurately, especially the strain at strength and the ultimate strain of confined concrete, modified formulae are proposed taking into account additional parameters which affect the characteristics of confined concrete, for example unconfined concrete strength. The comparison between experimental values of strength and strains and those predicted using the modified empirical model proves to be satisfactory. The relatively large scatter associated mainly with strain values, as well as the reliability of the available experimental results, is discussed.