Kings Bridge, South Esk River

Background

Kings Bridge was designed by William T. Doyne in 1861. At that time no facilities existed locally for the manufacture of a wrought iron arch and it was decided to have the girders manufactured by Charles de Bergue and Co. of Manchester, England, assembled in sections of a size suitable for shipping and sent to Launceston for final assembly. Kings Bridge met the needs of a growing community on the west bank of the Tamar River who were previously served by a punt which carried vehicles and stock. By 1860 there was increasing pressure on the West Tamar Road Trust to provide a bridge which would provide an uninterrupted service but the trust had not been able to find an economical solution. William T. Doyne arrived in Launceston in 1861 to survey and construct the Launceston to Deloraine railway and was engaged by the Trust to design a suitable bridge. The original bridge was single lane and was duplicated in 1904 to provide two traffic lanes, one in each direction.

Equipment and Subsequent History

Kings Bridge is a riveted wrought iron arch bridge spanning about 58 metres with a rise of 6 metres. It was constructed with two arch girders 4.6 metres apart, each girder being 1.2 metres in depth at mid-span and 500 mm wide. The total weight of the girders was 105 tonnes. The girders were fabricated by Charles de Bergue and Co and arrived in Launceston in July 1863. They were then assembled by Salisbury’s Engineering Works on a floating dock and taken to the site at high tide then allowed to settle in place on its abutments on the ebb tide. The deck was then formed of three rows of wrought iron plates 1.52 metres in width making up a total deck width of 4.56 metres. The bridge was opened on 11 December 1863. By 1900 original single-lane structure could no longer cope with the increased traffic demand and a decision was made to duplicate the bridge. A contract was let in 1903 to Salisbury Foundry to construct the new girders of stronger material to the original, but otherwise identical to the original girders. The new girders were erected on the same floating dock that had been used for the old arch and on 12 January 1904 the new girders were floated into place and then decked with wrought iron plates. The gap between the two structures was also decked creating a deck of 10.7 metres overall width. In 1988 an inspection of the road plates was undertaken which involved the removal of the road surfacing. The wrought iron plates were found to be in remarkably good condition and the only repairs required were along the plates edges where water had percolated through the surfacing.