Behaviour of Fiber-Reinforced Concrete Columns under Axially and Eccentrically Compressive Loads

An experimental investigation into the behavior of 16 short, confined, reinforced concrete columns with and without steel fibers was carried out. The columns with square sections had a concrete core 165 x 165 mm (6.49 x 6.49 in.) at the midsection and were hunched at the ends to apply eccentric loading and prevent boundary effects. The specimens were tested to failure at different strain rates under two loading schemes: concentric compression and eccentric compression with a constant eccentricity. The axial load and axial strains were obtained to evaluate the effects of the presence of steel fibers, the thickness of the cover concrete, and the eccentricity of the applied axial load. The comparative analysis of the experimental results showed that the presence of steel fibers delayed the spalling of concrete cover and increased the strain capacity and ductility; the eccentricity of the applied axial load caused substantial variation in the peak load, ultimate strength, and failure modes. Finally, the structural response of cross sections of normal concrete (NC) and steel fiber reinforced concrete (SFRC) columns subjected to compressive concentric and eccentric loading was numerically modeled to compare the experimental results. A suitable choice of constitutive laws for concrete and reinforcing steel bars and a reasonable calibration criterion of the model allowed for the reproduction of the experimental results with a good approximation level in terms of load-axial strain and the moment-curvature curves.