Historic bridges of New South Wales

Bridge construction in New South Wales started with the needs of the first settlers and continues through to the present day with advanced bridge design. The infant colony had limited expertise and limited materials. As time passed, techniques and materials were developed that allowed greater spans to be crossed and therefore expansion of the colony into otherwise inaccessible areas. The NSW Public Works Department was under pressure from a cash strapped government to produce as much road and bridge work for as little cost as possible. Timber truss bridges, and timber bridges generally were so common that NSW was known to travellers as the "timber bridge state". The following list illustrates the development of New South Wales bridge construction techniques. The list commences from the earlier constructions through to the later developments. ==New South Wales historic bridges==

Sorted by date 19th century } 20th century ==Allan type truss==

The Allan truss bridge is named after Percy Allan, a famous Australian engineer who designed this bridge type. His design consisted of vertical and diagonal arrangements comprising a combination of timber and iron elements. The timber elements were designed to be in compression and the iron elements in tension. Allen's design followed extensive testing of Australian hardwoods by Prof. Warren and his early engineering students at Sydney University. The timber used was mostly ironbark because of its high strength. Other features of Allan's truss design included design to minimize later maintenance and/or replacement of elements. For this reason the trusses were built in pairs to facilitate work on a particular element without requiring the whole bridge to be supported, as was the case with previous timber designs. Allan's design was very cost-effective. The Hampden Bridge in New South Wales Australia was the first of a larger style bridge to be built on Percy Allan’s design with the Tharwa Bridge pre-dating it. ==Dare type truss==

Harvey Dare was a leading engineer in the Public Works Department, and a prominent figure in early 20th century NSW. He was a designer of bridges and he developed the Dare Truss which was similar to the Allan truss but contained improvements which made them stronger and easier to maintain. This engineering enhancement represents a significant evolution of the design of timber truss bridges, and gives Dare trusses some technical significance. Dare Trusses were the fifth of the five stages of evolution of timber truss road bridges in NSW. In 1998 there were 27 surviving Dare trusses in NSW of the 40 built, and 82 timber truss road bridges survive from the over 400 built. == See also ==