The Eagleville Bridge employs " the patented Town lattice truss, consisting of top and bottom chords of laminated wood plank, and a web of diagonal wood planks connected by wood trunnels at each point of intersection ".
32.
The Shushan Bridge employs " the patented Town lattice truss, consisting of top and bottom chords of laminated wood plank, and a web of diagonal wood planks connected by wood trunnels at each point of intersection ".
33.
In 2006 the bridge saw minor structural repairs to its bottom chord at the upstream north corner, the bolsters were replaced for the first time since the hurricane of 1938, and the bed timbers were replaced by granite pedestals.
34.
However, in a tied-arch or bowstring bridge, these movements are restrained not by the abutments but by the bottom chord, which ties these tips together, taking the thrusts as tension, rather like the string of a bow that is being flattened.
35.
A "'tied-arch bridge "'is an arch bridge in which the outward-directed horizontal forces of the arch, or top chord, are borne as tension by the bottom chord ( either tie-rods or the deck itself ), rather than by the ground or the bridge foundations.
36.
For the next two decades many of Queensland's rail bridges were of the through Pratt design, including the half-through Pratt for lighter loads ( introduced 1909 ), which features top and bottom chords connected by vertical and diagonal members but no portal or lateral bracing between the two parallel trusses on either side of the rail deck.
