Recent vigorous economic growth in South East Asia has redistributed population and expanded industry and infrastructure building. Development of rural and remote regions required innovative engineering solutions to gain right of way to new land for extractive purposes, industry, urban development and the critical arteries of commerce – roads.
In countries where, historically, seaports and rivers were the main outlets, roads and bridges emerged to provide heavy load capability and more reliable and productive transport.
In this respect steel bridges were found well suited to the pace of development and challenging terrain. Offsite completion, orthodox freight to site and relatively simple erection were invaluable aids to the rapid expansion of the time.
The use of steel in bridge construction is not new, and knowledge of the manufacture and behaviour of this material is well understood where advancing design use of steel has resulted in economical and aesthetically pleasing bridge structures. Steel offers particular advantages in that it can be shop fabricated, under controlled conditions, to almost any desired cross sectional geometry to meet the specific strength requirement at each site, often at completely undeveloped locations.
However corrosion prevention is one essential factor in the economic utilisation of steel where provision of the appropriate protective coating can influence initial and whole of life cost, eliminate maintenance and lost service time, and defer the replacement date of structures.
A wide variety of products have been used for this purpose, however, many bridges require permanent maintenance teams to sustain adequate steel protection.
In most environments, after-fabrication galvanizing provides very suitable corrosion protection for steel and has a range of coating characteristics which make it unique. These include an alloy hardness greater than mild steel, a self-inspecting process discipline and predictable life directly proportional to its heavy coating thickness. These result in a surface alloy with competitive cost, resistance to severe impact, extended service life and in turn reliability for use in engineering calculations.
This issue of ‘galvanize!’ features the widespread use of hot dip galvanized steel ridges in the development of a number of South East Asian countries. Twenty-five years on, these are a tribute to many people and to the value of galvanized steel.
The Ma Tsao Bridge in Mount Yang Ming, North Taiwan, the earliest bridge to utilize after-fabrication hot dip galvanized steel, was opened in 1992. From then on, approximately 30 000 tonnes of steel and around 30–40 bridges have been hot dip galvanized. The most representative of these bridges are the Chung Cheng Overpass and the Linkou Bridge. There are now approximately 25 000 tonnes of bridges under construction which are the result of work by the galvanizing industry, with government and academia, in presenting proof of service of the hot dip galvanizing process, where security, low cost and reliability were crucial factors.
Taipei – Linkou Bridge
The Linkou Bridge is an 8-lane overpass bridge, 22.6 metres in width and 1065 metres in length, located in a non-sheltered environment adjacent to the seafront on the northeast coast of Taiwan. This girder type bridge utilized 7300 tonnes of galvanized 2 metre girders as well as 3030 tonnes of galvanized steel reinforcement to provide long-term corrosion protection in the salt-laden atmosphere of the Taiwan Strait.
Taipei – Chung Cheng Overpass Bridge
The Chung Cheng Overpass Bridge, opened in 1996, has 6 lanes, is 24.9 metres wide, 1672 metres in length and utilizes 7000 tonnes of hot dip galvanized steel girders. Heavy vehicular usage across the bridge and roads beneath, and the confined nature of the location with buildings in such close proximity, would make any bridge maintenance a major logistical problem.
Source: Galvanizers Association of Australia
For more information on this source please visit Galvanizers Association of Australia