Combined Torsion, Bending and Shear Analysis in Reinforced Concrete beams
This study investigates the effect of combined actions of torsion, bending and shear stresses on rectangular cross sectional plain and reinforced concrete beams at a given concrete mix design. The ultimate torsional strengths and angle of cracks of the beams were determined experimentally through a simple test arrangement set up on fifteen beam specimens grouped into five groups; BC1 to BC5. The combined loading was achieved through by loading the test beams at an eccentric distance away from the beam's principal axis at the midspan, through a system of Universal Testing Machine at the Engineering laboratory of the Standard Organization of Nigeria (Son) Enugu. Three international standard codes (BS 8110, Euro code 2 and ACI 318) were used to calculate the ultimate torsional strengths predicted for torsional resistance provided by longitudinal and transverse reinforcements and the strut of concrete cross section. The values obtained from the codes were compared with that of experimental results observation for validation. The ultimate torsional moments predicted by different classical theories (elastic, plastic, skew bending and Cowan's equations) were also used to calculate the ultimate torsional moments and compared with the experimental results. It was observed that the values predicted by the codes were not the same with each other and the experimental results in some cases while in other cases, the predicted values matches that of experimental results. This can be attributed to difference in certain assumptions, parameter and constants taken during the formulation of their respective equations which influenced the results. It was also observed from this study that ultimate torsional moments predicted by the classical theories are significantly difference from that of experimental results. It was concluded from the study that the angle of cracks used in design by different codes should not be fixed, but to be varied in other to obtain better economic and stable structures in terms of longitudinal and transverse reinforcements together with high concrete section that can sustain the applied