| Historical notes: | STATEMENT OF COUNTRY
Abercrombie Bridge over Abercrombie River is located within Wiradjuri Country and is the traditional home of the Burra Burra people. For many thousands of years, the area was used by Aboriginal people for traditional practises such as ceremony, fishing and resource gathering. The Abercrombie River is a tributary of the Lachlan River and the river is likely to have been a significant source of food and fresh water for Aboriginal people.
CONSTRUCTION AND RECONSTRUCTION OF ABERCROMBIE BRIDGE
A bridge was required at this location to convey produce from Crookwell and outlying settlements into Bathurst. The need arose due to the growth of agricultural industries which coincided with a massive influx of gold prospectors following reports of large discoveries (Berger: 2002, p2-3).
The original bridge at this location was a Bennett truss with three truss spans and an approach span on either side, supported on masonry piers. Tenders for the original bridge were called in September 1876, with J Ahearn the successful tenderer for the construction of the spans and GF Goodman the successful tenderer for construction of the piers (NSW Government Gazette 31 July 1877 p2938). Works commenced in 1877 and were still underway in July 1878.
The bridge was destroyed by flood in 1916. A temporary crossing was installed, but it too was swept away by flood in 1917. The four masonry piers from the original bridge survived the flood and were reused with their height extended with concrete. The length of the bridge was extended by construction of an additional span at both ends, supported by timber trestle piers built where the original abutments were located.
Photographs from the time of opening, and as late as 1947, show all the metal elements on the truss painted white, a deviation from the traditional colour scheme of timber elements painted white and metalwork painted black.
TIMBER TRUSS ROAD BRIDGES IN NSW
Timber truss road bridges have played a significant role in the expansion of the NSW road network. Between 1856 and 1936, over four hundred timber truss road bridges were built in NSW. Most of these bridges can be divided into five types. The Allan timber truss bridge, built between 1894 and 1929, and designed by Percy Allan, was the third type of timber truss bridge to be built in NSW. Key to Allan's design innovations were the ability to lighten the bridges and enable maintenance to be performed more easily.
The earlier timber truss bridges, designed between 1850s and 1880s, made use of the vast resource of large, strong and durable NSW hardwoods. However, much of it was exported, to the point where earlier types of timber truss bridges could no longer be built. The later bridges designed still made use of the strength and durability of NSW hardwoods but limited the maximum required size of these timbers to those still readily available. The five different truss types were a technical response to the changes in the availability of local timber resources.
PERCY ALLAN
Percy Allan joined the Roads and Bridges Branch in 1878 as a cadet after passing a qualifying examination. On completion, he was formally employed as an engineering draughtsman in the Drawing Office and was appointed Chief Draftsman in 1889. One of the major challenges to his Department came in the early 1890s marked by a period of economic depression in which most public works funding was curtailed.
Allan focused his energies on reworking the Howe truss from the United States. Allan's masterstroke was to apply the experience gained from involvement in the maintenance of the Old PWD and McDonald truss timber bridges by adopting twin timber members in the top and bottom chords. This twinning enabled the replacement of members under light traffic without the need for temporary support. Between 1893 and 1929, 105 "Allan truss" road bridges were built.
Allan is credited with the design of close to 600 bridges, including the Pyrmont Bridge and the Glebe Island Bridge. In 1900, he was appointed Supervising Engineer and later Principal Assistant Engineer for Rivers, Water Supply and Drainage, and in this role he supervised the completion of the low level sewerage system of Sydney which was a pumping system to replace harbour sewage outfalls. Other posts held by him included Engineer in Charge of Water Conservation and Artesian Boring (1904-06) and Principal Assistant Engineer for Water Conservation (1906), becoming Executive Engineer in 1907. In April, Allan was appointed president of the Hunter District Water Supply and Sewerage Board and PWD District Engineer at Newcastle. In 1911, he was promoted Chief Engineer for Public Works, Newcastle. From 1924, Allan had overall design responsibility for the Tom Uglys Bridge over the Georges River. Allan died suddenly of angina and cardiac failure on 7 May 1930. |