BEHAVIOR OF HIGH-STRENGTH CONCETE I-BEAMS WITH LOW SHEAR REINFORCEMENT

This paper describes an experimental study conducted on 10 simply supported I-beams containing low shear reinforcement ratios, including 4 reinforced concrete (RC) and 6 prestressed concrete (PSC) beams with concrete strengths ranging from 43-100 MPa. Results indicate that after critical diagnonal cracking, formation of arch action in RC beams provides sufficient reserve shear strength if adequate tension steel is provided. However, due to its higher cracking load approaching the arch action capacity, the reserve strength of PSC beams depends on the discrete number of stirrups intercepted by the inclined crack. Using the reserve shear strength index as a measure of safety, U.S. 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 herein. An equation is proposed for minimum shear reinforcement to ensure a consistent margin of safety for both RC and PSC beams.