Strength and deformability of confined high-strength concrete columns were investigated based on available experimental data. Up to 250 columns, tested either under monotonically increasing concentric loading or reversed lateral loading, were evaluated in terms of load, ductility, and drift capacities. The results indicate that the confinement requirements for high-strength concrete columns are significantly more stringent than those for normal strength concrete columns. However, it is possible to obtain ductile behavior in high-strength concrete columns through proper confinement. Although the requirements for volumetric ratio of confinement reinforcement are high for high-strength concrete columns, the use of high-strength confinement steel reduces the need to impose unrealistically high volumetric ratios to attain deformabilities usually expected of normal strength concrete columns. The results further indicate that the product of the volumetric ratio and strength of confinement steel, normalized with respect to concrete strength, can be used as a design parameter. Unconfined strength of concrete in column core was found to vary between 85 and 100 percent of the strength determined by a standard cylinder test. However cover in high-strength concrete columns may buckle prematurely under high compressive stresses when it is separated from the core by closely spaced reinforcement. This may result in strength reduction if the confinement of the core is not sufficient to compensate for instability of the cover.
