Performance of High-Strength Concrete (HSC) Columns Confined with Rectilinear Reinforcement

Strength and deformability of High-Strength Concrete (HSC) columns are presented based on recent experimental and analytical research. HSC columns under concentric compression and under combined axial compression and lateral load reversals are discussed. Experimentally observed column strengths are compared with those computed based on the provisions of ACI 318 (1) building code and analytical models proposed for HSC columns. The results indicate that the rectangular stress block currently used for normal-strength concrete is not applicable to HSC, especially for columns under high compression where the overall response is dominated by concrete. A triangular and a modified rectangular stress block is presented. Column capacity under concentric compression is illustrated with due considerations given to early spalling of cover concrete. Axial and lateral deformabilities of HSC columns are discussed with emphasis placed on the parameters of confinement. It is shown that HSC columns conforming to the current building code requirements may exhibit ductile behavior under moderate and low levels of axial compression. Higher grade lateral reinforcement can be utilized effectively to confine HSC columns to produce improved inelastic deformability under higher levels of axial compression.