Title: A Comparative Study of Confinement Models
Author(s): Shamim A. Sheikh
Publication: Journal Proceedings
Appears on pages(s): 296-306
Keywords: axial loads; bending moments; columns (supports); confined concrete;ductility; earthquakes; models; reinforced concrete; stress-strain relationships;structural analysis; structural design; tied columns; ties (reinforcement).
Various analytical models available in the Iitera ture for the confinement of concrete by rectilinear ties are studied. These models are applied to the specimens tested by the author as well as by other investigators to predict the results. Loadings on these specimens include axial and combined axial and bending, monotonic as well as cyclic. In the case of cyclic loading, only the envelope curves are determined using the analytical models. Experimental results are compared with results predicted by various models. It is concluded that in addition to the commonly acknowledged variables such as the amount of lateral reinforcement and steel strength, two other variables play important roles in determining the behavior of the confined concrete. These variables are the distribution of the longitudinal steel around the core perimeter and the resulting tie configuration, and the spacing of ties. Better distribution of steel and closer spacing of ties along the column longitudinal axis (for the same amount of reinforcement) result in higher concrete strength and ductility. Analytical results from the model accounting for these variables show the best agreement with experimental results.