Puentes curvos

CHAPTER 1
Introduction
At one time, bridges on curved alignments were rare; however, modern highway bridges and traffic separation structures are commonly built on a horizontal curve. This changehas come about because of higher traffic volumes and speeds, the geometric constraints of the urban environment, and improved structural forms that lend themselves to curved construction.
The concretebox-girder, particularly post-tensioned prestressed concrete that can span large distances, is one such structural form. The cross section of these structures is inherently strong in torsion. This isimportant because curvature induces high torsion forces. Also, because concrete can be easily molded into the required shape, it is ideal for curved construction. For these reasons, prestressedconcrete box-girders have become the structure type of choice in many jurisdictions. A common application of curved structures is in freeway interchanges where connector ramps or “fly-overs” carry traffic fromone freeway to another at relatively high speed. Cross sections of curved box-girders may consist of single-cell, multi-cell or spread box beams as shown in Figure 1-1. Because only a very few spreadbox beam bridges use curved beams, only the first two types were considered in this study.
It has become common practice to analyze and design these structures as if they were straight. Live loaddistribution is often addressed using the whole-width design approach. Local problems, such as the lateral forces induced by curved prestressing ducts, are often handled using specific design rules anddetails that have been developed over the years. For the most part, this design approach has been used successfully, but some recent cases of poor bridge performance have made it clear that thisapproach has its limitations.
Because it is likely that (1) the use of curved structures is going to increase and (2) the geometries of some of these structures will continue to push the limits with...