Lattice truss bridge

A lattice bridge is a form of truss bridge that uses many small, closely spaced diagonal elements forming a lattice. The lattice Truss Bridge was patented in 1820 by architect Ithiel Town.

Lattice Truss Bridge
Interior structure of a covered bridge utilizing a plank-lattice structure
AncestorTruss bridge
RelatedNone
DescendantNone
CarriesPedestrians, livestock, vehicles
Span rangeshort to medium
Materialwood planks and beams or steel angles and beams, appropriate decking material
MovableNo
Design effortmedium
Falsework requiredSometimes

Originally a design to allow a substantial bridge to be made from planks employing lower–skilled labor, rather than heavy timbers and more expensive carpenters, this type of bridge 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.

Belfast truss
Belfast truss as roof support in an aircraft hangar from the First World War at the Duxford Imperial War Museum

The Belfast truss is a cross between the 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 24 metres (79 ft) had been achieved, and in the 20th century, shipyards and airplane hangars demanded ever greater clear spans.[1]

Wood lattice truss bridges
Root Road Covered Bridge, Ashtabula County, Ohio

Iron or steel lattice truss bridges
Railroad bridge across the Iowa River in Iowa City, Iowa.

Howard Carroll built the first completely wrought-iron lattice truss bridge. This was built for the New York Central Railroad in 1859.[2]

See also

References
  1. J. R. Gilfillan, S. G. Gilbert, The Historic Belfast Timber Truss - A Way to Promote Sustainable Roof Construction, 2002.
  2. J. A. L. Waddell, Bridge Engineering Vol. 1, Wiley, New York, 1916; page 23.
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