Limited ductility design of reinforced concrete columns for tall buildings in low to moderate seismicity regions

Abstract

Nonlinear moment-curvature analysis using stress-strain relationships of the constitutive materials and take into account the stress path dependence of longitudinal steel was performed to study the structural parameters affecting the flexural ductility of high-strength reinforced concrete (HSRC) columns. From the analysis, a theoretical equation for designing square-shaped limited ductility HSRC columns was proposed that correlates the volumetric ratio of confining reinforcement within critical region to the cross-section core area ratio, yield strengths of longitudinal and confining reinforcement, area ratio of longitudinal reinforcement, concrete strength and compressive axial load level. The validity of the proposed theoretical equation was verified by testing eight square-shaped columns with concrete cylinder strength varied from 50 to 96 MPa and longitudinal steel ratio from 0.9 to 6.1% that contained the proposed content of confining reinforcement within the critical region of columns. Outside the critical region, the confining steel is designed based on ultimate shear demand. The columns were tested under reversed cyclic inelastic displacements and compressive axial load, whose magnitude was held constant throughout the test. From the test results, it was observed that the ultimate curvature ductility factor obtained for these columns were about 10, which are considered to behave in a limited ductility manner. © 2010 John Wiley & Sons, Ltd.