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Bridges & Buildings Strengthened With Plastic

09 Aug

source: http://www.monash.edu.au/pubs/eureka/Eureka_95/plastic.html

Monash researchers are working with Australian and American companies to develop methods to strengthen bridges, buildings and other forms of civil infrastructure with plastic composites.

Chairman of the Department of Mechanical Engineering, Professor Rhys Jones, believes plastic composites have the potential to become the building materials of the 21st century.

While many people might wonder at the concept of driving plastic cars, flying in plastic aeroplanes, sailing in plastic ships and driving over plastic bridges, Professor Jones says those days are not far away.

And contrary to what cynics might say, he believes that using these advanced plastics as building materials will be much kinder to the environment.

He is quick to point out that the new plastics technology is much more sophisticated than that used to create the multitude of plastic household and office products we use daily.

“We are referring to advanced plastic composite materials,” Professor Jones said. “We already have the technology; we just need Australian designers and manufacturers with the skill and courage to develop the products.”

He said Monash research into advanced composites had shown they were more durable than steel and concrete, with the added benefits of being low-cost, lightweight, energy-absorbent and less corrosive.

He defined a composite as “generally a relatively stiff fibre in a relatively soft resin or matrix”. The substance which holds the fibre in place is often a polymer. Fibreglass, for example, is a well-known plastic composite, comprising fibre in a polymer resin.

Composite building materials have been used throughout history. “One very good example is the mud brick, which the Egyptians made by mixing straw and mud,” he said. “Wood and paper are also composites, as they are fibre-reinforced materials.”

Professor Jones was previously head of structural engineering with the Department of Defence before joining Monash a few years ago.

He said advanced composites technology was developed primarily for military applications, including the repair of high-performance fighter aircraft.

Aside from military uses, the civil applications for the new composites technology are immense.

Advanced composite `wraps’, for example, can be applied to buildings, freeway bridges and other structures in earthquake-prone regions to make them more resistant to damage.

“What generally happens to a steel-reinforced concrete building or bridge during an earthquake is that the concrete cracks and falls out of the structure. The steel bars inside the concrete are left unsupported; they then buckle and collapse and the structure falls down,” Professor Jones explained.

“What we have found at Monash is that simple plastic `wraps’ around such concrete structures can increase their strength more than four-fold.”

These `wraps’ are often only a few millimetres thick and consist of a fibreglass-graphite composite.

The concrete inside a `wrapped’ structure is still likely to crack in an earthquake, but the covering holds the bulk together, protecting the steel supports and preventing the overall structure from collapsing.

“You only have to stop one freeway from collapsing and save one life, and it’s all worthwhile,” Professor Jones said.

He stressed that advanced composites were not direct competitors to concrete or steel. “They are synergistic, because composites will mostly be used to increase the capabilities of the other materials, rather than replace them.”

A 1991 report from the US Secretary of Transport stated that almost 40 per cent of the country’s bridges were “structurally deficient or functionally obsolete”. Governments worldwide are currently facing huge repair bills on infrastructure.

“In South Australia alone it is anticipated that by the year 2010 the entire state budget will be taken up in refurbishing corroded infrastructure,” Professor Jones said.

He believed the increased use of composites was also in keeping with Australia’s aims to reduce air pollution and create a `greener’ environment.

The material is lighter, meaning that cars, ships and aircraft built using composites will, theoretically, fly faster and use less fuel.

“One of the major environmental problems we face is pollution from car engines,” he said.

“If you can expend less fuel, your car will give off fewer gases, and if the car is lighter in the first place it will use less fuel.”

There is also a safety element, as composites are highly energy-absorbent and once incorporated into vehicle designs can increase the safety of passengers in collisions.

Professor Jones said that while there would always be a degree of conservatism and scepticism about using plastics technology, “new composite building materials will, if we can present innovative design, give Australia a chance to grab major international contracts”.

“What’s so good about Monash is that all these capabilities can be found in the one institution and are complemented by experimental test facilities that are rare outside the US and Europe.

“This makes the university a natural resource for the Asia-Pacific region in the area of advanced composites.”

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2 Comments

Posted by on August 9, 2007 in General Knowledge, R&D

 

2 responses to “Bridges & Buildings Strengthened With Plastic

  1. santos

    August 9, 2007 at 10:56 am

     

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