Hydraulic Design of Highway Culverts - DOT On-Line Publications

Figure VI-37--Typical Long Span Culvert Shapes
1. Structural Aspects. Long span culverts depend on interaction with the earth embankment
for structural stability. Therefore, proper bedding and selection and compaction of backfill are of
utmost importance. For multiple barrel structures, care must be taken to avoid unbalanced loads
during backfilling. Some manufacturers of long span culverts will not sell their products to a
client unless the design and installation is supervised by their engineers. If this is not required,
the project should be coordinated with the manufacturer's engineering staff.
Various manufacturers utilize different techniques to achieve the desired long span
configuration. In some instances, reinforcing ribs are used to strengthen the structure. In other
cases, specially designed longitudinal structural stiffeners are installed on the top arch. Ribs and
stiffeners which project into the barrel may increase the hydraulic resistance, particularly if the
elements are perpendicular to the flow.
Anchorage of the ends of long span culverts is required to prevent flotation or damage due to
high velocities at the inlet. This is especially true for mitered inlets. Severe miters and skews are
not recommended.
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