Buckling Behaviour of Slender High-Strength Concrete Columns

Abstract

A numerical method for predicting the behaviour of a reinforced concrete column is proposed, using the layered finite element method. To investigate the effects of concrete strength and longitudinal steel ratio on the ultimate load and axial force-bending moment relation of a column, a series of tests was carried out for 30 tied reinforced concrete columns with a 80 mm square cross-section a nd three slenderness ratios of 10, 60 and 100. Th ree different concrete strengths of 25.5, 63.5 and 86.2 MPa, and two different longitudinal steel ratios of 1.98 and 3.95% were used. The boundary conditions at the ends were both hinged and end eccentricities (24 mm) were equal and of the same sign. Experimental results revealed that the ultimate load for a short high-strength concrete column was significantly increased but not for a slender column. The possibility of stability failure for a slender column was increased with the increase of concrete strength. The increment of ultimate load due to increase in longitudinal reinforcement for the short column was less than for the slender one, and the heavier reinforcement for the slender column led to a more stable column. The predicted behaviours of the concrete columns by the numerical method proposed herein show good agreement with the test results, they also show that the ACl's moment magnifier method may be unconservative for very slender high-strength concrete column.