Design of Confining Reinforcement in Columns For Seismic Performance
S. A. Sheikh
Appears on pages(s):
axial load; confined concrete columns;
Professor S. M. Uzumeri and the author initiated a research program on the seismic resistance of reinforced concrete columns in mid seventies. The first phase of this work concentrated on the behavior of rectilinearly confined concrete columns under axial compression. In addition to carrying out an extensive experimental program, an analytical model for the mechanism of concrete confinement by rectilinear transverse reinforcement was developed. This was followed by an investigation of square columns under combined axial load and flexure. After identifying the important variables that affected the mechanism of confinement and section behavior, the research advanced to a study of column behavior under simulated earthquake loads. Distribution of longitudinal and lateral reinforcement, level of axial load, spacing of ties and the type of lateral support provided to the longitudinal bars were found to significantly affect the ductile performance of a column. Based on the results from extensive experimental and analytical research, a design procedure was developed in which the amount of tie reinforcement and the detailing of both longitudinal and lateral reinforcement are determined for a required ductile performance of a column subjected to a given axial load. This paper presents selected results from the work carried out over the last several years. An example demonstrating the application of the design procedure is also included.