Town lattice truss

Lattice Truss Bridge

Interior structure of a covered bridge utilizing a plank-lattice structure
Ancestor	Truss bridge
Related	None
Descendant	None
Carries	Pedestrians, , vehicles
Span range	short to medium
Material	wood planks and beams or steel angles and beams, appropriate decking material
Movable	No
Design effort	medium
Falsework required	Sometimes

A lattice bridge is a form of truss bridge that uses a large number of small and closely spaced diagonal elements that form a lattice. It was patented by architect Ithiel Town in 1820 and 1835 as Town's lattice truss.

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 a large number of 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 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 meters had been achieved, and in the 20th century, shipyards and airplane hangars demanded ever greater clear spans.

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