Steel truss bridges - Computational Analysis and Design of Bridge Structures - page 315

Table 10.2 Stringer sections for Tydings Bridge
Stringer

End spans Intermediate spans

A, B, C, D, F W24 × 76 W24 × 76

E, G W24 × 84 W24 × 76

Table 10.3 Stringer spacing for Tydings Bridge
Spacing

Distance

A-B, B-C, C-D, F-G 2.06 m (6 ′ -9 ″ )

D-E 1.89 m (6 ′ -3/16 ″ )

E-F 1.32 m (4 ′ -4 ″ )

entire structure. The sections used in the design are shown in Table 10.2,
while the spacing is shown in Table 10.3.

10.5.1 thermal analysis
This study finds the main cause of the premature cracks of the expan-
sion plates as shown in the insertion of Figure 10.17 (Fu and Zhang
2010). A 2D truss model is built by TRAP to study the bridge behavior
under thermal loads. In long-span truss bridges, spandrel-braced arch
bridge, or called cantilever truss bridge, is a very popular type. Rigid
arms extend from both sides of two piers. Diagonal steel trusses, pro-
jecting from the top and bottom of each pier, hold the arms in place.
The arms that project toward the middle are supported only on one side,
like strong cantilever arms, and support a third, central span. Changes
of temperature cause material to contract or expand due to the effect of
thermal contraction or expansion.
Originally, the bridge sliding plate system was designed assuming that
plates would slide on horizontal surfaces when the bridge contracts or
expands. However, a closer scrutiny of the behavior indicates that the
sliding plate action was affected by the complex movement between
anchor spans and suspension spans as well as the force-release systems.
A thermal model as shown in Figure 10.19 was generated for the thermal
analysis.
The temperature change is assumed to the extreme of 130°F (54.4°C),
the difference between the highest and the lowest temperature for the
sliding plate design. x - and y -movements are plotted along the panel
point. Figure 10.20 shows the expansion of the x -movement of the