This paper proposes provisions to extend the current American Association of State Highway and Transportation Officials�? AASHTO LRFD Bridge Design Specifications to include prediction of the ultimate flexural strength of prestressed concrete girders with concrete compressive strengths up to 18 ksi (124 MPa). The proposed design provisions include composite action of a high-strength concrete (HSC) girder with normal-strength concrete (NSC) deck slab. Nine 40-ft-long (12 m) AASHTO Type II HSC gird- ers were tested with and without cast-in-place NSC decks of differing widths to achieve various possible modes of failure. The concrete used for the girder was designed r three target compressive strengths of 10 ksi, 14 ksi, and 18 ksi (69 MPa, 97 MPa, and 124 MPa). The experimental program investigated failure modes of three different types of compression zones: one with NSC only, one with HSC only, and one with both NSC and HSC. All girders were tested to failure under static loading to study the different limit-state behaviors, including prestress losses, initiation of cracking, yielding, and final failure mode.
