Shear Strength and Behavior of High-Strength Concrete Prestressed Beams

Current design provisions for shear strength in AASHTO LRFD 2012 and ACI 318-14 have a limit on the compressive concrete strength of 10,000 psi (69 MPa) based on empirical evidence. In this paper, the requirements for minimum transverse reinforcement and maximum shear strength were evaluated for high-strength concrete. Four AASHTO Type I prestressed beams with concrete compressive strengths from 10,000 to 15,000 psi (69 to 105 MPa), and shear reinforcement ratios rho(v)f(yv) near the minimum (326 psi [2.3 MPa]) and maximum (1305 psi [9.0 MPa]) limits were tested. The key findings in this paper supported the adequacy of the prescribed minimum amount of shear reinforcement in both design documents with regard to reserve strength after first inclined cracking and adequate crack control for service loads. However, an upper limit for the nominal shear strength of 12 root f(c)' is recommended for members with concrete compressive strengths up to 15,000 psi (105 MPa).