PERFORMANCE OF RC. SHORT COLUMNS UNDER BI-DIRECTIONAL SEISMIC INPUT

Abstract

Short columns are structural zones of high shear strain concentrations, which very often fail in an explosively brittle manner, during even moderate intensity earthquake shaking. Evidence of failure in frame columns exhibited their vulnerability when subjected to seismic demands, despite the conservative design philosophy adopted by current practice. Hence, updating the present codes or providing new design techniques is urgently required. This mandates a complete reassessment of short column response to seismic excitations. The present work was initiated to investigate, experimentally and analytically, the performance of short columns subjected to biaxial shear due to seismic input. A review of the available research work and code provisions was undertaken. Experiments of twelve reinforced concrete short columns subjected to cyclic loading in directions skewed with respect to the principal axes of the specimens as well as loading in directions of the principal axes were reported. The set-up, instrumentation, control and specimen manufactures were presented alongwith a full description of the experimental results. The analytical study is carried out to develop a new mathematical model for columns shear capacity. Based on the results of the experimental and analytical investigations, comparative studies were furnished alongside implications of the main finding on the ductility­ based earthquake resistant design process.