Confining Reinforcement for Concrete Columns

Abstract

Previously derived stress‐strain relationships for compressed concrete confined by various quantities and arrangements of transverse reinforcement are used in cyclic moment‐curvature analyses of a range of reinforced concrete columns to derive design charts. The design charts permit the enhanced flexural strength of confined columns to be obtained. They also permit the quantities of transverse reinforcement required to achieve particular curvature‐ductility factors in the potential plastic‐hinge regions of reinforced concrete columns to be determined. The column section is considered to have reached its available ultimate curvature when either the moment resisted has reduced to 80% of the ideal flexural strength, or the strain energy absorbed in the transverse reinforcement has reached its strain energy absorption capacity, or when the logitudinal steel has reached its limiting tensile or compressive strain, whichever occurs first. Refined design equations to determine the quantities of transverse reinforcement required for specified ductility levels are derived on the basis of the design charts. The equations are an improvement on the current provisions of concrete design codes.