Menangle Railway Bridge and Viaduct, Menangle, New South Wales

Together with its sister bridge over the Nepean River at Penrith, the Menangle Railway Bridge is the oldest surviving rail bridge in New South Wales. It was built under the direction of John Whitton when the railway was originally put through. The bridge carries the Main South Line over both Menangle Road and the Nepean River, linking Menangle Park and Menangle. It features multiple 51 metre spans supported by concrete-clad sandstone piers. Each span is a cellular wrought iron box girder with decorative ribs. Extra piers were built in 1927 to add support in floods.

The railway bridge was built in 1863 by Messers Peto, Brassey and Betts. Also known as Menangle rail bridge over Nepean River and Menangle Railway Bridge, it was the first large iron railway bridge erected in New South Wales and was the first large iron railway bridge on the New South Wales Government Railways network. The first large railway bridge was an eight-span stone arch viaduct, was opened at Lewisham in 1855.

Opened on 1 July 1863 with the line from Campbelltown station to Picton station, Menangle Railway Bridge was manufactured in England by The Canada Works in Birkenhead. The bridge opened. In 1907, the bridge was strengthened with intermediate piers and extra girders added.

When John Whitton planned the railway extension from Campbelltown to Picton, he was under pressure from the Government to keep costs low by using as much local material as possible. A metal girder design had been proposed by contractors Peto, Brassey and Betts but Whitton substituted a timber bridge made from ironbark and other strong hardwoods, a relatively short 151 metres, low level crossing.



However the flood of 1860, some 18.3 metres above the proposed rail level, caused him to design a high level, large span bridge to maximise the waterway, flanked by long timber approach viaducts, a total of 582 metres. It was a massive structure for its time, comprising 4,518 cubic metres of masonry, 833 cubic metres of brickwork and 849 tonnes; 836 long tons tons of wrought iron for a total cost of A£94,562.

The iron superstructure was manufactured in England at the Canada Works, Birkenhead (opposite Liverpool) and shipped out in December 1861. One ship arrived in Sydney in April 1862 but the other was wrecked at the entrance to the Mersey River. However, the replacement ironwork was delivered to Sydney in December 1862. Construction of the locally quarried sandstone abutments and piers were completed in October 1862 and the iron bridge was assembled ready for service by June 1863. Load testing, by three locomotives in full steam, followed and the line to Picton was opened on 1 July 1863.



The use of a continuous superstructure was technically significant because the analysis of such structures was a relatively new, sophisticated procedure. Also, it showed that Whitton and Fowler (London) appreciated the structural benefits that a continuous girder over three spans offered compared to three simply-supported spans.

Since 1907, when intermediate piers were built in the middle of the three original 49.4-metre spans, the bridge has six 24.2-metre spans. Between the original stone abutments, these additional brick piers alternate with the original stone piers. The superstructure consists of two massive, wrought iron, cellular (box) girders, continuous from abutment to abutment, no breaks at the piers. These 3.8-metre deep girders are at 7.8-metre (26 ft) centres which allows for a double track between them, supported on a series of closely spaced cross girders.

On the outer surfaces of the girders there are pairs of curved angle iron suggesting the inclusion of an arch. These are purely decorative, there is no arch action, the superstructure is a girder. At the Sydney end, one of the ornamental tops to a pier was demolished by a derailment in 1976. The iron bridge received only localised superficial damage but the stonework was not replaced, thereby leaving the cellular cross section of the girder exposed.


Victoria Bridge, Penrith

The sister bridge to the Menangle Bridge is the Victoria Bridge over the Nepean River at Penrith. Their sizes and design were such that they were featured in an international text book Modern Examples of Road and Railway Bridges by William H. Maw and James Dredge, London, 1872.