| Historical notes: | HISTORY OF IRON OR STEEL ROAD BRIDGES IN NSW
The very first Cast Iron bridge was built over the Seven River at Coalbrookdale in England in 1776. However, iron was not used in bridge construction in New South Wales until many years after the colony was founded. This was due to a wealth of strong, durable Australian hardwood timbers that were suited for use in bridge construction, the distance of Australia from overseas markets and the delay and expense involved in importing materials.
Deposits of iron were fist discovered in NSW in the Mittagong district in 1833, although the discovery was not exploited until 1848. This heralded the iron industry in this country and was the first location in Australia where iron was smelted. The settlements of Nattai, New Sheffield, Fitzroy and Mittagong grew up around the Fitzroy Iron Works founded in 1859.
Iron was mainly used in bridge construction for foundation piers, especially at locations where heavy flooding was known to occur. The construction of the first iron bridge in NSW was over Wallis Creek at Maitland in 1851 from British iron. It had three wrought iron girder spans with an overall length of 170 feet. This bridge has since been replaced.
Bar iron, the first product of the Fitzroy Iron Works, arrived in Sydney in December 1863. In 1864-65 the Company was commissioned to cast the cylinders and other iron works for the Prince Alfred Bridge to be built over the Murrumbidgee River at Gundagai. Each pier cylinder was six feet long, six feet in diameter and over one inch in thickness. Each cylinder was cast in one piece and weighed two and a half tons; these cylinders were the largest castings of iron made in NSW at that time. Three iron truss spans, each 103 feet in length, were used to span the main river channel.
In 1870 the Macquarie River at Bathurst was re-bridged with an iron structure, replacing a former timber bridge that had been destroyed by floods in 1867. This bridge exists to this day. With the exception of the heaviest of plates, this bridge was built from materials produced in NSW at the Pyrmont Rolling Mills using iron from Fitzroy Iron Works.
Economic quantities of structural steel, as opposed to wrought iron, did not being to arrive until the 1890s. This coincided with the change from British to American bridge technology. British bridge technology had until then produced sturdy, heavier, lattice bridges made from larger quantities of weaker wrought iron, this compared to more lightweight American bridge trusses made from the stronger metal, steel. By 1900, the use of steel had replaced wrought iron virtually world wide and its dominance in civil and structural engineering design has continued ever since.
In the first two decades of the twentieth century, timber continued to be a material of choice in NSW bridge construction, as a locally available material, particularly in rural areas. However, the wider use of steel truss bridges or concrete beam bridges and the decline of the use of timber truss bridges was clearly evident by 1930. This was principally due to increasing traffic loads and a requirement for wider bridge decks. Seasoned timber of the required size and lengths was increasingly difficult to obtain and becoming very expensive. In addition, timber trusses required frequent maintenance and it was inherent in these bridge types that their capacity to carry traffic generally decreased with age. The Main Roads Act, 1924-1931, addressed the absence of sufficient bridges as one if its priorities.
The construction of Sydney Harbour Bridge between 1924 and 1932, designed by English firm, Dorman Long and Company, led to a new age in the construction of steel road bridges in NSW. At the time of construction and until recently it was the longest single span arch bridge in the world and is still the largest in terms of mass. Sydney Harbour Bridge is considered to be one of the most remarkable feats of bridge construction undertaken. Its construction is riveted steel.
During the 1930s the Department of Main Roads pioneered the use of welding in the fabrication of steel bridges, particularly for trusses where riveting and bolting were becoming un-economic. This pioneering work led to the development of longer spans, enabling the construction of Peats Ferry Road Bridge between 1939 and 1945. Designed and construction supervised by the Department of Main Roads and fabricated by the Clyde Engineering Company, Granville, NSW, the two K-truss spans - each 438 feet long - were the longest welded truss spans in the world when built. The caisson foundations for the bridge to the river bed are also of high technical achievement, due to the difficult geology of the Hawkesbury basin. One caisson pier extends 241 feet and 4 inches below low water level, just 8 inches short of the world record depth for a bridge foundation at that time, held by Bay Bridge, San Francisco.
By the 1950s further developments in the design, construction and maintenance costs of steel bridges had achieved further economies. Reinforced concrete decks were used compositely with steel span members, increasing span lengths and reducing the weight of steel used. High tensile steel bolts for field joints had replaced riveting and new methods of retarding corrosion had been developed, thereby reducing maintenance costs. Despite these improvements, the use of steel in bridge design in NSW had declined, not because material was unsuitable, but due to a growing appreciation of the potential for reinforced concrete for bridge construction.
PREVIOUS CROSSINGS AT PEATS FERRY
The Hunter River was first discovered shortly after the arrival of the First Fleet and a settlement was established at Newcastle in 1801. Initial communication from Sydney was by sea and for some years the only means of land travel was by Howes Track, following approximately the current road from Windsor through Richmond, Putty and Bulga to Singleton. In 1830, the route to Wiseman's Ferry and Wollombi was opened to vehicular t traffic and became the principal route for overland travel between Sydney and the Hunter River.
Shortly after the road via Wiseman's Ferry was opened, George Peat, a ship builder, obtained grants of land either side of the Hawkesbury Rive at Kangaroo Pint and Mooney Point. He used this land for cattle grazing. To send his cattle to market he built on the river bank a two masted sailing lugger for use between the two points.
The presence of Peat's boat encouraged travellers to use the shorter route as an alternative to Wiseman's Ferry, although this remained the better developed route. Travellers between Sydney and Brisbane Water also used Peat's boat and by 1845 the lugger was in use as a ferry between Kangaroo Point and Mooney Point. In 1847, George Peat developed Peat's Ferry Road (now the Pacific Highway) as a track from Sawyer's Road at Berowra Valley to Kangaroo Point.
No record exists of the period 1860 to 1888 but it is believed that a James Cole operated a private punt between Kangaroo Point and Mooney Point. However, the circuitous route via Wiseman's Ferry remained a more improved and more popular route with travellers. On the opening of the railway line to Newcastle in 1886, crossing the Hawkesbury River at nearby Brooklyn, Peat's Ferry ceased to operate and it was not until 1930 that a ferry service was re-established.
The first motor lorry arrived in 1908 and motor vehicle transport steadily replaced steam and horse drawn transport.
By the 1920s there was extreme pressure for improved and new roads. The Main Roads Board was established in 1925 and one of its first undertakings was to construct a new sealed highway from Hookham's Corner at Hornsby to Peat's Ferry. Originally called the Great North Road, it was soon to become known as the Pacific Highway. The road was completed in 1930 and the first of two diesel ferries for motor vehicles, the George Peat and Frances Peat, became operational. These ferries operated up until World War 2 when they were removed to serve in New Guinea.
The construction of the current bridge commenced in 1939 and was completed in 1945. |