Failure and Strength of High-Strength Concrete Columns Subjected to Eccentric Loads

The objective of this paper is to verify the basic design rules of high-strength concrete columns. A total of 32 column specimens were tested to investigate structural behavior and strength of eccentrically loaded reinforced concrete tied columns. Main variables included in this test program were concrete compressive strength, steel amount, eccentricity, and slenderness ratio. The concrete compressive strength varied from 34.9 to 93.2 MPa, and the longitudinal steel ratios were between 1.13 and 5.51%. Test results of column sectional strength are compared with the results of analyses by ACI rectangular stress block, trapezoidal stress block, and modified rectangular stress block. Axial force-moment-curvature analysis is also performed for predicting axial loadmoment strength and compared with the test results. The ACI rectangular stress block provides overestimated column strengths for the lightly reinforced high-strength column specimens. The calculated strengths by moment-curvature analyses are highly affected by k3 values of the concrete stress-strain curve. Observed failure mode, concrete ultimate strain, and stress block parameters are discussed.