Development of a Computer-Aided Algorithm to Determine the Floor Wise Column Size for Multi-storey Base-Isolated RC Frame Buildings

This paper introduces a computer-aided, program-based algorithm to assess the potential floor-wise column size for direct displacement-based design of base-isolated reinforced concrete frame buildings. Lead rubber bearings are considered as base isolator for the base-isolated systems. The design storey drifts are kept low as base-isolated buildings are mostly intended to achieve a low storey drift fully operational performance level under spectrum-compatible ground motions. The frame deformation components considered in the algorithm are column tip displacement due to flexure, average column displacement due to shear, and joint rotation due to flexure and shear. To account for the dynamic amplification due to the inter-storey drift ratio, a regression line equation is evaluated from the developed relationship between design and target drifts. An approximate transformation relationship of effective toward the fundamental period for isolated buildings is also introduced to control and account for the dynamic amplification of column moment and shear. Results of time history analyses show that the proposed method effectively determines the storey-wise column size for various building plans, heights up to 12 stories, and design base displacements up to 350 mm for target storey drifts up to 0.25%.