Simplified Procedure to Obtain LRFD Preliminary Design Charts for Simple-Span Prestressed Concrete Bridge Girders

摘要

The latest bridge design manual from the Precast/Prestressed Concrete Institute (PCI) provides preliminary design charts for selecting the girder size and prestressing strands for a given span length and beam spacing but only for f'_c = 55 MPa and 0.6-in. (15-mm) diameter strands. This single concrete strength and strand size may limit the use of the charts, particularly in states considering high- and ultrahigh-performance concrete. Accordingly, this paper presents a simplified procedure to develop preliminary design charts for prestressed concrete bulb-tee girders based on the American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD) bridge design specifications considering service load stress limits and flexural strength. The procedure is demonstrated for a BT-72 section and new LRFD charts are generated to compare the effects of higher concrete strength and larger strand size on bridge girder design. The benefits and limitations of the approach and recommendations for future implementation are discussed.