A Methodology for Estimating the Axial Response ofConfined Concrete

The axial strain-axial stress behavior of confinedconcrete plays a vital role in the design of concretecolumn members; hence an accurate prediction of thestress-strain behavior is needed. In this work, the axial response of plain concreteunder varying confining pressure was examined using anovel triaxial cell mechanism. This work examinesrealistic levels of constant, linear elastic, elastic- perfectly plastic, and elastic-hardening varyingconfinement, typical of fiber reinforced polymer andsteel jacketing applications. It is found that theaxial stress-strain response of confined concrete isdependent on the variation of confining pressureapplied. A unique model for estimating the axial response ofconcrete under varying or constant levels ofconfinement is developed with using the results fromcompanion experimental program. The model is based onthe variation of the confining pressure due to thelateral dilation of the concrete. The model is shownto provide an accurate prediction ofhistoricalexperimental studies of constant confinement tests oncylinders, FRP jacketed specimens, and columnsconfined with conventional lateral reinforcement orFRP jackets.