HIGH-STRENGTH PLAIN CONCRETE DEEP BEAMS UNDER TORSION

Twenty high-strength plain concrete deep beams were tested under pure torsion. The variables were concrete strength, cross-sectional area and depth/width ratio. Concrete strengths of 50, 66, 79 and 90 MPa, cross-sectional areas ranging from 32,000 to 160,000 mm(2) and depth/width ratios varying from 1 to 5 were used. The tested beams failed suddenly and violently along a smooth surface. The crack inclinations of the failure surfaces were influenced by the primary design variables. The increase of the concrete strength and the cross-sectional area, as well as the decrease of the depth/width ratio increase the beam strength and stiffness. Theoretical equations available in the literature were used to predict the torsional strengths and they gave a good estimate of the experimental values.