ABSTRACT
Due to urban development, more curved alignments, longer spans, more skewed supports, and more segmental construction for concrete bridges are expected. Construction methods can be cast in place with shoring or precast, curved, spliced “U” girders with a cast-in-place deck. Based on survey (Nutt and Valentine 2008) in the NCHRP report 620, except the western United States, most states are tending toward segmental construction (cantilever and span by span using both precast and cast-in-place concrete) to avoid conflict with traffic. A common application of curved structures is in freeway curved alignment or interchanges. Cross sections of curved box girders may consist of single-cell, multicell, or spread box beams, as shown in Figure 6.1. In the United States, only a very few spread box beams are used for curved concrete bridges. As for the requirement of a more refined analysis, many U.S. states use an 800-foot (244-m) radius as the trigger where designers should consider three-dimensional (3D) analysis, such as a grillage or finite element analysis (FEA) described in Chapter 5.
