as a multispan bridge. Although bridges may be either
fixed or floating, only fixed bridges are covered in this
training manual (TRAMAN). The following
information covers the components of a fixed bridge.
The substructure supports the superstructure and
consists of abutments, footings, sills, posts, bracing, and
There are different types of fixed-bridge abutments.
First, lets cover the footing type of abutment. In figure
8-2, views (A) and (C) show two types of footing
abutments. View (A) shows a timber-sill abutment, and
both of these views, you will see that three elements are
common to a footing type of abutment. Specially each
type has a footing, a sill, and an end dam.
Notice that the timber-sill abutment shown in figure
8-2, view (A), is the same footing type of abutment
shown for the bridge in figure 8-1. In this type of
abutment, loads are transmitted from the bridge
stringers to the sill which distributes the load to the
footing. The footing then distributes the combined load
over a sufficient area to keep the support from sinking
into the ground. The end dam is a wall of planks that
keeps the approach-road backfill from caving in
between the stringers. The timber-sill abutment should
not be more than 3 feet high. It can be used to support
view (C) shows a timber-bent abutment. By studying
spans up to 25 feet long,
Figure 8-2.Types of fixed-bridge abutments.