A lattice truss bridge is a form of truss bridge that uses many small, closely spaced diagonal elements forming a lattice. The design was patented in 1820 by architect Ithiel Town.
Originally a means of erecting a substantial bridge from mere planks employing lower - skilled labor, rather than heavy timbers and more expensive carpenters and equipment, the lattice truss has also been constructed using many relatively light iron or steel members. The individual elements are more easily handled by the construction workers, but the bridge also requires substantial support during construction. A simple lattice truss will transform the applied loads into a thrust, as the bridge will tend to change length under load. This is resisted by pinning the lattice members to the top and bottom chords, which are more substantial than the lattice members, but which may also be fabricated from relatively small elements rather than large beams.
The Belfast truss is a cross between Town's lattice truss and the bowstring truss. It was developed in Ireland as a wide-span shallow rise roof truss for industrial structures. McTear & Co of Belfast, Ireland began fabricating these trusses in wood starting around 1866. By 1899, spans of 24m (79feet) had been achieved, and in the 20th century, shipyards and airplane hangars demanded ever greater clear spans.[1]
Howard Carroll built the first completely wrought-iron lattice truss bridge. This was built for the New York Central Railroad in 1859.[2]