Proposal for Concrete Compressive Strength up to 18 ksi (124 MPa) for Bridge Design

An extensive experimental and analytical research program was undertaken to recommend revisions to extend the applicability of flexural and compression design provisions for reinforced and prestressed concrete members of the AASHTO LRFD Bridge Design Specifications to concrete compressive strengths up to 18 ksi (124 MPa). The recommended provisions are intended to be seamless and unified over the full range of concrete strengths. The experimental program included tests of material properties; flexural, axial compression, and combined axial and flexure tests of reinforced concrete members; and flexural tests of prestressed concrete members. From the measured test results and the analytical study came several recommendations to revise the specifications; these include modulus of elasticity, modulus of rupture, creep and shrinkage, rectangular stress block parameters for flexural design, minimum area of prestressed, and nonprestressed longitudinal reinforcement for compression members and prestressed girders. The 4-year research program was sponsored by NCHRP and TRB.