Behavior of Square and Low-Strength Concrete Columns Reinforced with Hybrid Steel Bars and Micro-Fibers

Steel fibers increase the strain capacity of normal and high-strength concrete columns. Availability of normal or high-strength concrete and conventional reinforcement is limited for low-rise concrete houses in rural areas. It is in the interest of society, of the thousands of people that live in those houses, that house performance be evaluated. This paper assesses the behavior of 18 short, square-section columns made of low-strength concrete reinforced with hybrid steel bars and micro-fibers under axial compressive loads. The investigated variables were the steel ratio (2.8% and 5.6%) and layout of transverse reinforcement and the fiber dosage (10 kg/m(3)and 20 kg/m(3)). Response of the specimens was assessed in terms of crack patterns and failure modes, compressive stress-strain curves and the contribution of concrete, conventional steel reinforcement and steel fibers to the performance of the columns. Experimental stress-strain curves of the columns were compared with those computed using existing analytical models. The comparison of the measured and calculated stress-strain curves showed that it is required to calibrate a model for the columns with the key characteristics included in the experimental campaign. The study developed a behavioral model that is consistent with the trends of the results measured. The effectiveness of the proposed model was evaluated through statistical analysis.