Curved precast prestressed concrete girder bridges.

摘要

Precast concrete stringer type girders for curved bridges can be a viable alternative to traditional curved steel girders and cast-in-place post-tensioned concrete box girders. This relatively new technology has already been implemented in Pennsylvania, Nebraska, and Colorado and is being considered in Florida, Texas and other locations. Despite the fact that it has been shown to be competitive with conventional curved bridge superstructures, the author believes that significant simplifications can still be achieved.;A new system is introduced to frame curved bridges utilizing precast prestressed concrete girders. The new system is proposed to be competitive to the existing precast concrete and steel systems. The main feature introduced here for the first time is use of relatively short (40-ft.) girder segments in a straight line precasting facilities. The segments are then joined and post-tensioned to form "curved" girder. In most applications, even for relatively sharp curvatures, the visual impact of deviation of these chords from a true curve in minimal. It is shown that there are cost advantages over existing systems. Another feature of the proposed system is utilizing for the first time the most cost-effective standard I-girder shape for sharp curvature. The forms can be used repeatedly in straight-line prestressing beds, which results in economical production. A full span can be assembled on the ground and post-tensioned before the full span girder is shipped and erected. The construction steps of the proposed system follow the same construction sequence for straight bridge girders. With these improvements, precast concrete would be the most dominant system for curved bridges.;This dissertation gives a complete system description, construction stage considerations, analysis and design methodology, and experimental investigations. Design methodology is outlined to consider the effects of warping torsional stresses. Furthermore, a design example for a two-span bridge with sharp curvature is being designed and detailed. This information can be a guide for bridge designers to design and detail curved concrete bridges considering the advantages of new system.