EXPERIMENTAL TESTS ON ECCENTRICALLY LOADED HIGH-STRENGTH CONCRETE COLUMNS

Reported in this paper are the rest results for 68 eccentrically loade d conventional and high-strength concrete columns. The columns were 15 0 x 150 mm (5.91 x 5.91 in) at the mid-section and haunched at the end s to apply the eccentric loading and prevent boundary effects. Concret e strengths used were 40, 55, 75, and 90 M.B.A. (5800, 8000, 10,900, a nd 13,100 psi) with load eccentricities of 8, 20, and 50 mm (0.32, 0.7 9, and 1.97 in). The columns had either 2 or 4 percent longitudinal re inforcement and tie spacings of 30, 60, or 120 nun (1.81, 2.36, or 4.7 2 in). The ultimate strength of the columns is compared to the strengt h predictions based on the ACI 318-89 rectangular stress block paramet ers. The predictions compare reasonably well, although lower strengths than predicted occurred for some high-strength concrete specimens. Du ctilities are calculated based on the area under the load versus avera ge strain plus curvature times eccentricity relationship. This measure showed a weak correlation with the confinement parameter adopted. Str ains in the tie reinforcement were measured al the side face for some of the medium and high- strength concrete columns. The measured strain s were not at yield when the peak load was reached.