A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Engineering and Technology

Thesis (M.Eng.) - Asian Institute of Technology, 1991

Many investigations of confined concrete column have already been conducted in the past. However, since almost all investigations in the past are based on experiments alone, which do not give a clear understanding of mechanism of confined concrete column and are not unified, analytical study of the mechanism of confined concrete column was conducted by using three-dimensional Finite Element Analysis. The results fell between those from the formulations proposed by other researchers. Some experimental investigations were also conducted to verify the concrete material model and the result from Finite Element Analysis for steel-encased concrete columns. Three influencing factors to the strength and ductility, namely shape of lateral tie, volumetric ratio of lateral reinforcement to concrete core, ratio of spacing of lateral reinforcement to the width of concrete core, were studied. Three types of lateral reinforcement shape, circular tie, rectangular with cross tie and rectangular without cross tie, were studied. The circular tie is the most effective, and rectangular without cross tie is the least. The increment of volumetric ratio of lateral rein forcement to concrete core does not necessarily increase the strength and ductility of confined concrete column. It depends on the stress condition in the ties. The ratio of spacing of lateral reinforcement to the width of concrete core affects the strength and ductility in longitudinal and lateral directions. The smaller the ratio, the greater the confinement that can be mobilized to cross section far from lateral reinforcement and also the greater the mean stress level in the ties. Once the ties yield, strength and ductility increments will decrease.