Innovative System for Curved Precast Posttensioned Concrete I-Girder and U-Girder Bridges

A new system for framing curved bridges using precast prestressed concrete girders is introduced. The main feature of the new system is the use of relatively short [6-12 m (20-40 ft)] straight girder segments that are joined and posttensioned to form a full-length curved girder. The visual impact of the deviation of these chords from a true curve is indistinguishable by a casual observer. However, it greatly simplifies production of precast curved girders, which are currently produced in full-span piece lengths. Another feature of the new system is utilization of two of the most commonly used precast concrete girder shapes: I-girder and U-girder. The straight-line bridge girder forms and prestressing bed can be used for the proposed curved girder system, saving considerable initial capital and allowing more precasters to compete for this type of bridge. The result is a better value of the cost-effective precast concrete stringer system compared to curved steel, cast-in-place concrete, and segmental precast systems. This paper presents the components of the new system and proposed construction stages. It also presents an overview of the analytical and experimental investigations conducted to evaluate the constructability and structural performance of the proposed system. Preliminary design aids are presented to assist in determining suitable girder size for different span lengths and radii of curvature.