STRENGTH AND DISPLACEMENT CHARACTERISTICS OF CONCRETE BEAMS REINFORCED WITH STEEL BARS OF EQUAL AREA BUT DIFFERENT DIAMETERS

Abstract

This research presents an investigation on the strength and displacement characteristics of bending strength of concrete beams reinforced with steel bars of equal area but different diameters. The test beams comprise two (2) each of 100mm x 100mm x 500mm and 150mm x 150mm x 750mm unreinforced beams as control beams, and two (2) each of 100mm x 100mm x 500mm and 150mm x 150mm x 750mm beams were reinforced in turn with 20mm, 16mm, 12mm, and 10mm bar diameters of about 943mm2 area of reinforcement, bringing the total number of concrete beams cast to twenty (20) including the control beams. The beams were subjected to centre-point loading using bending testing machine (Model Cat.C11/O), in accordance with BS 1881:118, and with the load and compressive strain recorded to the point of failure. The results of the test beams showed that the greatest difference in the area of reinforcement between beams reinforced with 9Y12 bars (bar area = 1020mm2) and 3Y20 bars (bar area = 943mm2) is 7.5%; whereas the difference in the moments of resistance of the same reinforced beams is 26.5 and 21.8%, for both the 100mm x 100mm x 500mm and the 150mm x 150mm x 750mm beams respectively. The results also showed that given the same area of steel in a cross section, the section with the greater number of bars has higher bending strength, moment of resistance, and the modulus of elasticity, as well as lower deflection values.