Steel truss bridges - Computational Analysis and Design of Bridge Structures - page 303

Figure 10.6 The Golden Gate Marin (north) approach viaduct under construction.
10.2.2 cantilevered truss bridges
A cantilever truss bridge is a structure in which at least one portion
acts as an anchorage for sustaining another portion that extends beyond
the supporting pier. The use of cantilevers allows for the construction
of much longer bridge spans. A cantilevered bridge uses two horizon-
tally projected beams that are supported on piers. Counterbalancing
spans called anchor arms provide tension and suspension through the
truss. Cantilevered truss bridges remained popular through most of
the twentieth century until cable-stayed bridges became more com-
mon. The most famous early cantilever bridge is the Forth Rail Bridge
(Figure 10.7). This bridge held the record for the longest span in the
world for 27 years only to be surpassed by the Quebec Bridge in 1917,
which is still the current record holder. The Tydings Bridge of Maryland
is an illustrated example of this type of cantilever bridge and will be
shown later.
Steel truss cantilevers, as shown in Figure 10.8, support loads by
the tension of the upper members and compression of the lower ones.
Commonly, the structure distributes the tension via the anchor arms
to the outermost supports, whereas the compression is carried to the