Building bridges

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NASA general manager Warwick Ironmonger.

As the Middle East develops, so too do the techniques and trends for bridge construction. CW discovers the systems used to save time, energy and materials.

Twenty or so years ago, bridges passing through the Middle East were built to run over vast open deserts with few obstacles to contend with.

Now, new highways are going live, islands are being built at sea and buildings are rising from the sands. Bridges have to get over such obstructions and, as a result, their design and construction has had to become much more advanced.

Saving time

One of the knock-on effects of a developing city is the rise in population, which leads to congestion. So, when building bridges, contractors now have to work faster to avoid interfering with other infrastructure.

"Constructing a bridge is often a significant degree more complicated than building other structures, given the presence of live waterways, roads, and railways," says Warwick Ironmonger general manager of Nasa Structural Systems in the Middle East, which offers services in post-tensioning, external pre-stressing, stay cables, heavy lifting and strengthening.

"These [obstacles] may not only restrict access but often demand the completion of the structure in the shortest possible time to minimise the disturbance of existing traffic."

Consultants working on the Al Wadha Road project in Sharjah, UAE were given just two years to close one of the emirate's busiest highways in order to carry out their work, which included the construction of a 550m-long viaduct.

RJR Engineering is one company that offers a solution aimed at meeting the needs of developers who need to construct a bridge quickly and effectively.

The company supplies a system that can be moved along a bridge without dismantling. The system has unique features, which enable quick and easy assembling.

"We can move the system three times without dismantling it. If you have lots of repetition, you don't need to keep taking it up and down, you can move the whole system as a big chunk," says RJR managing director Roger Ratcliffe.

"The equipment is robust, thus ideally suited to the rough and tumble conditions on civil engineering sites. It is not unusual to see our large tables being carried between structures with large all-terrain fork lifts."

RJR has supplied its formwork to the completed Sheikh Khalifa Bridge, as well as over 300 bridge structures across the UAE.

"Bridge construction, if in situ, is very much formwork dictated and the choice of a fast, efficient system is imperative to speedy and quality related work."

Maintaining quality

Construction in the Middle East was once about watching a city grow and come to life, now developers need to take into account the long-term effects on their projects.

Premature corrosion of concrete structures, such as bridges, is a growing problem here, especially in marine environments. This can result in the need for regular maintenance, which often comes at a hefty price.

But, according to Torben Krebs, general manger for Arminox, a leading supplier of stainless steel reinforcement, many contractors are blind to this fact.

"Although we have seen a lot of futuristic structures coming up over the past two decades, construction is still very traditional in the Gulf," he says.

There are two reasons behind this. One: the developer likes to use the same old systems and the same old materials. "He knows the setbacks, but he believes he can handle it."

As a result, Krebs predicts that the Gulf will soon experience an unexpected explosion in maintenance and repair costs, to be allocated to existing but quite new structures.

"The second reason is the fact that any change in design or research into new materials means application of man hours," he continues. "Therefore, unfortunately, we see specifications for designs or products, which would never be used in Europe or the US."

Epoxy coated reinforcement, increased concrete cover, chemical inhibitors and cathodic protection have been tested on structures, such as bridges, but failed to protect the concrete against corrosion.

Krebs believes there is only one solution for this problem: "If stainless steel reinforcement is introduced in the corrosion zones of the structures, there will be no corrosion and grades of stainless steel with a guaranteed lifetime of more than 150 years are now commercially available."

Arminox has worked on projects such as Pearl Qatar Bridges and Site Causeway Bridges in Bahrain.

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