| Concern about the shear capacity of large, lightly reinforced high-strength concrete beams was the motivation for this investigation. The objectives of this study were to investigate the influence of concrete strength and main longitudinal reinforcement ratio on the shear capacity of large, lightly reinforced concrete members with, and without, transverse reinforcement. In addition, the test results were used to assess the performance of the North American code provisions, ACI 318-95 and CSA A23.3-94 (General Method).;The following observations and conclusions resulted from this study: (i) Overall, the General Method yielded much better predictions than the ACI approach. For the 12 tests, the average ratio of the experimental shear failure load to the predicted shear failure load for the ACI Method and the General Method was 0.74 (Coefficient of Variation = 23%) and 0.98 (C.O.V. = 15.3%), respectively. (ii) The five beam specimens constructed with 1% longitudinal reinforcement, without stirrups, and concrete strengths of 20 MPa, 32 MPa, 38 MPa, 65 MPa, and 80 MPa, respectively, had essentially the same ultimate shear capacity. No benefit was realized in the shear capacity, for the higher strength concrete beams. In fact, the beam specimen with the 80 MPa concrete had the lowest shear capacity. (iii) The implementation of high-strength concrete proved to be beneficial only when transverse reinforcement was utilized. |
