Toward the Performance-Based Design of Confined Concrete

This paper summarizes results from a comprehensive research program that aims at developing rational guidelines for the design of confinement reinforcement in concrete columns. The first part of the paper briefly introduces an analytical model for confined concrete in tied columns. The model is based on the results of testing 24 square columns with various tie configurations under concentric compression. The second part presents results from square columns tested under cyclic flexure and shear, and constant axial load simulating earthquake loads. The specimens tested included normal-strength concrete (NSC) and high-strength concrete (HSC) columns confined by steel and NSC columns confined by fiber-reinforced polymers (FRP). Performance-based procedures for the design of confinement reinforcement in these columns are proposed in light of the experimental results and analytical models. The design procedures incorporate various ductility parameters that include energy dissipation capacity, ductility factors, and cumulative ductility indices in addition to the type, amount, and configuration of the confinement reinforcement and the level of axial load. The areas in which further research is needed are also discussed.