||Technology in Australia 1788-1988
Table of Contents
I Construction During The Settlement Years
II The Use Of Timber As A Structural Material
III Structural Steel
IV Concrete Technology
VI Industrialised Pre-cast Concrete Housing
VII Ports And Harbours
IX Heavy Foundations
XII Water Engineering
XIV Major Buildings
XVI Thermal Power Stations
XVII Materials Handling
XVIII Oil Industry
XIX The Snowy Mountains Scheme
XX The Sydney Opera House
XXI The Sydney Harbour Bridge
XXII Hamersley Iron
XXIII North West Shelf
Sources and References
These early runways first consisted of a thin layer of soft rock or natural gravel, placed over the natural surface. As aircraft wheel loadings and tyre pressures became larger, stronger pavements with higher standards of materials were required, with more attention to sub-grades, drainage and runway surfaces. Increased frequency of aircraft movements, and the need for smooth, clean surfaces, required the sealing of them.
Australian technology applied to airport pavement design has, since the early 1950s, included particular attention to tyre pressures. Experience has shown that good grassed natural surfaces can sustain aircraft with tyre pressures up to about 350 kPa. Pavements of natural hill or river gravel can be suitable for aircraft until tyre pressures reach about 700 kPa. For higher tyre pressures, crushed rock is usually needed. Pavements of crushed rock, surfaced with a thin layer of bituminous concrete, have proved satisfactory for the largest aircraft in existence today with tyre pressures around 1500 kPa.
Extensive runway development took place during the Second World War years, constructed by authorities such as RAAF and U.S. Army construction units, the Civil Construction Corps, Commonwealth Works Department, State Road Departments and local Councils. The methods and materials used were understandably directed towards speed of construction rather than permanence. Nevertheless, some 138 runways were of permanent value and formed the basis for the development of an airport network throughout Australia.
With many other requirements for the manpower and material resources available in the years following the war, a policy was introduced restricting, temporarily, development of country airports to a standard suitable for the Douglas DC3, which could operate on natural surfaces or light runway pavements of low-cost materials. The introduction of the Convair (21,300 Kg) and Douglas DC6 (44,000 Kg) in 1948, and the Viscount (29,300 Kg) in 1954, with tyre pressures of 500 to 600 kPa, brought a requirement for stronger, smoother pavements, first at capital city airports and later, as traffic increased, at major country airports. Lockheed Electras (51,000 Kg and 900 kPa) in 1958 brought the need for crushed rock. Boeing 707s (112,000 Kg and 1150 kPa) in 1959, and Boeing 747s (365,000 Kg on tandem wheel assemblies and 1250 kPa) in 1971, required stronger and smoother runway pavements and the use of bituminous concrete for the surface layer.
Technology used for runway and other airport pavement design is generally similar to that for road engineering. There are, however, important differences in the stresses imposed by aircraft compared with motor vehicles. Aircraft wheel loadings, tyre pressures and operating speeds are much higher, but the frequency of loadings is much lower. There are high horizontal surface shearing stresses on the point of touchdown; torsional stresses in short radius turns on aprons and ends of runways; severe vibrational and shearing effects from reversing propeller pitch or jet blast after landing; large downward thrust coupled with high velocity, and high temperature jet blast on the pavement at the point of rotation of some jet aircraft. The smooth, relatively flat surfaces of runways can cause aircraft to aquaplane when landing in heavy rain.
After the war, the Commonwealth Department of Works & Housing (DWH), later to become the Department of Housing & Construction (DHC), developed and extended the existing road engineering technologies of various States to deal with the particular problems of both civil and defence airfield pavements. Basing their work on the California Bearing Ratio (CBR) method of determining depths and characteristics of flexible pavements and Westergaard's theories of concrete (rigid pavements), DWH developed its own methods and technology to suit Australian climatic and other conditions, such as relatively dry sub-grades and low traffic densities at many airports.
Organisations in Australian Science at Work - Australia. Department of Housing and Construction (D.H.C.); Australia. Department of Works and Housing (D.W.H.); Royal Australian Air Force (R.A.A.F.)
People in Bright Sparcs - Bradfield, Dr K. N. E.; Westergaard, H. M.
© 1988 Print Edition pages 394 - 395, Online Edition 2000
Published by Australian Science and Technology Heritage Centre, using the Web Academic Resource Publisher