Behavior of concentrically loaded high performance concrete tied columns

The paper presents an experimental study of behavior of high performance concrete (HPC) columns under monotonic concentric loading. The test variables include strength of concrete, amount and spacing of transverse reinforcement, configuration of ties and amount and yield strength of longitudinal reinforcement. Concentrically loaded columns of HPC are characterized by early cover spalling due to the plain of separation formed between the cover and core. The equation in codes and literature to predict the axial load capacity of columns were based on tests of normal strength concrete (NSC). Hence, use of existing code equation leads to overestimation of concentric load capacities. The failure pattern is sequenced by the buckling of longitudinal bars, yielding of lateral ties and rupture of ties. The test results indicate decrease in the spacing of lateral ties and increase in volumetric ratio of transverse steel, increases marginally the strength but largely the ductility. Also an equation is proposed such that the prediction of axial load capacity is neither overestimated nor too conservative.