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The paper presents test results on 20 high-strength fiber reinforced concrete square columns subjected to concentric and eccentric loading. The study aim was to examine the effect of the weight of steel fibers on the strength and behavior of HSC columns under concentric and eccentric loading. All columns were longitudinally reinforced with 4 GFRP bars 6 mm diameter, and two steel bars 10 mm diameter, making the reinforcement ratio (ρg = 0.0181), and steel ties at 64 mm spacing. The studied test variables included the steel fiber weight ratio and the eccentricity. To prevent premature spalling in the concrete cover, it was discovered that it helps to add steel fibers to HSC mixtures in concrete columns. In addition, this also increases the strength of eccentrically loaded reinforced columns compared to that for concentrically loaded columns. The strength and behavior were predicted also by the proposed method. The predicted and the experimental results found to be in a good agreement.

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Reinforced concrete members may be subjected to axial load, bending moment, shear and torsion. However the behaviour of these members under shear or combined shear and torsion is a complex phenomenon. In this study the softened truss model theory is applied for the analysis of fibre reinforced concrete deep beams and corbels. The theory is more promising than the strut and tie model which satisfies the equilibrium conditions and to some extent materials constitutive relationships. While this theory, considers the equilibrium, compatibility, materials constitutive relationships and the degrading effect of the diagonal tension cracks on the compressive strength of cracked reinforced concrete element when subjected to biaxial compression-tension stresses. The previously developed algorithms for the analysis were modified by incorporating the effect of short discrete steel fibres on the behaviour and strength of concrete subjected to shear. Fibre reinforced concrete deep beams and corbels were analyzed using the adopted algorithm and materials constitutive relationships. The predicted effects of the shear span / depth ratio, volume fraction of steel fibres and the longitudinal steel ratio on the shear strength of fibre reinforced concrete deep beams and corbels showed good agreement with published experimental results.

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