Behavior of high-strength concrete I-beams with low shear reinforcement

Abstract

An experimental investigation was carried out on a total of 10 simply supported I-beams containing low shear reinforcement ratios. These include four reinforced concrete (RC) and six prestressed concrete (PSC) beams with concrete strengths ranging from 43 to 100 MPa. Test results indicate that after critical diagonal cracking, formation of arch action in RC beams provides sufficient reserve shear strength if adequate tension steel is provided. In contrast, due to its higher cracking load that approaches the arch action capacity, the reserve strength of PSC beams depends on the discrete number of the stirrups intercepted by the inclined crack. Using the reserve shear strength index as a measure of safety, American and Canadian code provisions, with respect to the minimum shear reinforcement, are found to be inadequate in guaranteeing a satisfactory margin of safety in PSC beams investigated in this study. Based on the present tests and those available in the literature, an equation is proposed for minimum shear reinforcement to ensure a consistent margin of safety for both RC and PSC beams.