Analytical Performance of Reinforced Concrete Columns using Various Confinement Models

Abstract

Accuracy of various stress-strain relationship models for concrete confined by lateral steel reinforcement in prediction of the moment-curvature response of a section under various loading patterns was investigated. Fiber model was implemented in a computer program developed for flexural analysis of reinforced concrete columns. Both monotonic and hysteretic analysis were performed. Each confined concrete model was used in the analysis for several loading cases on a circular, and a loading case on a rectangular section, keeping all other parameters fixed. Results were compared to each other and also validated against experimental data from six large-scale reinforced concrete circular columns and a rectangular section tested under the analyzed loading cases. In general, analysis underestimated the moment and overestimated the curvature capacities under a high level of axial load regardless of the model used, and there was a better agreement between analysis and test for low level or no axial load. Results from various models were close to each other, though different from test results, for cases with a constant or proportionally variable axial load. For a monotonic curvature with non-proportionally variable axial load, predictions by some recent models had a better agreement with experimental data. Evidently the level of axial load, and in turn the depth of compression zone, is related to the degree of confinement-utilization, and affects the confined concrete behavior. This is rarely addressed by the models.