Torsion, Shear, and Bending on Stirruped L-Beams

Test results on reinforced concrete L-beams with closed stirrups under combined torsion, shear, and flexure are reported. Emphasis is placed on beams having less longitudinal steel than required to develop the full potential shear strength of the beams, that is, beams which in the absence of torsion would fail in flexure. Based on test data an interaction surface is defined for L-beams with symmetrical top and bottom steel which checks test results closely. Stiffness in torsion before and after diagonal cracking is examined. The large drop in stiffness after initial diagonal cracking under combined loadings is examined. Measurements of strain show additional stresses in longitudinal bars resulting from torsion, but stresses of significance only after diagonal cracking. The total demand for longitudinal steel is perhaps not as great as the sum of that required for moment and torsion calculated separately.