Introduction - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 15

Figure 1.17 A pony truss bridge ( bphod.com ) .
Figure 1.18 An old-fashioned riveted truss bridge ( pbase.com ) .
connected by welding to replace the old-fashioned riveted bridge shown in
Figure 1.18 . However, in case of continuous bridges and long-span bridges,
it is more convenient to divide the bridge into separate welded parts that are
connected to the construction field by bolted connections.
Let us now look in more detail to the structural components of a tra-
ditional railway bridge. Figure 1.19 shows the general layout of a double-
track open-timber floor plate girder railway steel bridge. A train track of
this railway bridge consists of a pair of rails resting on timber sleepers.
For a single track, the sleepers are supported by two longitudinal steel
beams known as stringers . The stringers are spaced at specified distances
( a 3 ), given by the national code of practice in the country of construction,
depending on the spacing between rails and the spacing between center-
linesoftrains( a 2 ), in case of more than a single track. The stringers are
supported on cross steel beams known as cross girders .Thecrossgirders