Curved concrete bridges - Computational Analysis and Design of Bridge Structures - page 171

Curved concrete bridges
6.1 BasiCs of Curved ConCrete Bridges
6.1.1 introduction
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 pre-
cast, curved, spliced “U” girders with a cast-in-place deck. Based on survey
(Nutt and Valentine 2008) in the NCHRP report 620, except the west-
ern 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.
Sennah and Kennedy (2002) present highlights of references pertain-
ing to straight and curved box girder bridges in the form of single-cell,
multiple-spine, and multicell cross sections. The elastic analysis techniques
discussed include the following:
1. Orthotropic plate theory method
2. Grillage analogy method
3. Folded plate method
4. Finite strip method
5. Finite element method (FEM)
The orthotropic plate method lumps the stiffness of the deck, webs,
soffit, and diaphragms into an equivalent orthotropic plate. In the grillage
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