The effects of fibers on the confinement models for concrete columns

Abstract

A mathematical model is developed to express the stress–strain relationships in compression of fiber-reinforced concrete (FRC) columns for both normal- and high-strength concrete, with and without conventional steel reinforcement. This model allows one to determine the maximum strength and strain capacity by determining the effective concrete core of the confining devices at rupture. Analytical expressions are also given for the ultimate load corresponding to the complete formation of the concrete failure plane. The proposed model incorporates the most relevant parameters of confinement, i.e., type of confinement, volumetric ratio, spacing, yielding strength, shape of the member cross section, type of fiber (length, diameter, shape), and fiber volume. The model has been verified against data obtained from concentric compressive tests on concrete specimens reinforced with transverse steel and fibers.Key words: high-strength concrete, fiber-reinforced concrete, lateral reinforcement, stress–strain curves.