Optimized Sections for High-Strength Concrete Bridge Girders

摘要

The objectives of this investigation were: to identify the limitations ofexisting prestressed concrete girder cross sections relative to the use of high-strength concrete; to examine the feasibility of using modified cross sections to take advantage of the high-strength concretes; to investigate the use of alternative construction systems; and to define factors that limit the application of high-strength concrete. The research was performed using the computer program 'BRIDGE' to determine relative unit costs and maximum span lengths for different simple-span prestressed concrete bridge designs. The analysis indicated that the use of existing girder cross sections with concrete compressive strengths up to 10,000 psi (69 MPa) allow longer span lengths and more economical structures. To effectively utilize higher strength concretes, additional prestressing force must be applied to the cross section in the form of smaller strand spacings, larger strand sizes, higher strength strands, or post-tensioning. The Bulb-Tee should continue to be considered as a national standard for span lengths from 80 to 200 ft (24 to 61 m). However, the Washington and Colorado sections are equivalent up to span lengths of 120 ft (37 m), and the Florida and University of Nebraska sections are slightly more economical for span lengths greater than 150 ft (46 m).