COMPARATIVE STUDY OF STRENGTH OF TRUSS REINFORCED CONCRETE BEAM AND CONVENTIONAL REINFORCED CONCRETE BEAM

ABSTRACT

This work presents comparative study of strength of truss reinforced concrete beam and conventional reinforced concrete beam. Two sets of 0.15 x 0.15 x 1m beams were cast. One set was cast using truss as a system of reinforcement at spacing of 100mm, 150mm and 200mm. The other set was cast using longitudinal bars and links at spacing of 100mm, 150mm, and 200mm as the conventional reinforcement. In all 27 truss and 27 conventional reinforcement beams were cast. Three mix ratios were used for this work, namely, 0.5:1:2:4, 0.55:1:2.5:5, and 0.6:1:3:6. Each mix ratio was used to cast nine truss reinforced concrete beams, nine conventional reinforced concrete beams, and three concrete cubes. The quantities of these mix ratios were calculated and batched by weight, mixed and placed in 0.15 x 0.15 x 1m beam mould and 0.15 x 0.15 x 0.15 cube mould. Fifty four beams and nine cubes were cast so as to determine the flexural strength of the beams and the compressive strength of the concrete cubes respectively. The cast beams and cubes were left for 24hrs before they were demolded and were totally submerged in an open curing tank for twenty eight days. The cubes were crushed using concrete compressive testing machine and the beams were also loaded to failure using Magnus frame at twenty eighth day. The loads that crushed each of the cubes were recorded and compressive strengths were calculated from their corresponding loads. Also the failure load of each of the beams was recorded and the flexural strength of the beams calculated using their corresponding loads. The 28-day compressive strength of the concrete was found to be 33.40N/mm2 and flexural strength of the truss beam is 1292.27kN/m2 against 1071.82kN/m2 for conventional reinforcement. A computer program was written on truss analysis within the range of 1000mm span in which all the forces in the truss members were generated with the aid of a polynomial established from graph of spacing against points loads. From this study, the following conclusions were drawn: truss reinforced concrete beam has greater strength than the conventional reinforced concrete beam; the higher the compressive strength the higher the flexural strength of the beam; a computer program can be used as alternative to manual truss analysis. Further research should be carried out on this using sandcrete and flat bars reinforcement.

Keywords: Truss reinforcement, Conventional reinforcement, Granite, Concrete, Beam, Compressive strength, Flexural strength.