PRECO – Innovative construction technique cuts costs and building time
Infrastructure is a funny thing. No one notices it when it operates smoothly. But one little problem is all it takes for it to move to the top of everyone's list of annoyances.
While anyone can appreciate why yearlong detours caused by construction lead to high levels of frustration, few pause to reflect that without infrastructure, European citizens' great privilege of being able to move freely across the EU's 27 member states' borders to live and work would be nothing but an idealistic fantasy. Perhaps more than any other structure, bridges - which literally span gaps and traverse barriers - represent that privilege. Yet their construction in particular is notorious for taking years. And even then end results oftentimes have an awkwardly heavy design.
All that may soon change thanks to a new construction technology known by its acronym Preco-Beam (which stands for Prefabricated Enduring Composite beams based on innovative shear transmission). By combining steel and concrete in prefabricated composite structures with reinforced concrete slabs, the European Union (EU)-funded Preco-Beam project found a way to shave months off construction times while bringing to market a sleeker, cheaper, more environmentally friendly bridge design.
"This project was a great example of research moving seamlessly into application," Project Officer Jonas Hedberg said of Preco-Beam, which ran from 2006 to 2009 and received € 838,000 in EU funding. Already now eight new railway bridges using Preco-Beam have been built in Germany, Austria and Poland. "The main innovative feature of this technology," says Hedberg, "is the way the steel connects to concrete, by a structure known as the composite dowel."
Previously, connectors were headed studs (a kind of large nail with flattened end) made of steel. "But using headed studs has disadvantages," explains Project Coordinator Dr. Günter Seidl, from the German consulting engineering company SSF Ingenieure. "Our technology results in great savings of steel and thus leads to significant cost reduction. There are also less maintenance costs because the constructions are extremely long lasting. This is thanks to the composite dowel we use, which provides a very ductile connection and yields high safety-levels for infrastructure users.
The Preco-Beam consortium invented a new shape for this composite dowel, which connects steel and concrete: namely an I-section which can be divided into two steel T-beams by one simple cut. "Through this new system we can make much slenderer bridges than was previously possible, which require 40 percent less steel," Seidl says proudly of the project's achievements. "Prefabricating the parts in a controlled workshop not only improves their quality, it also means we now only need days rather than months on site to erect the bridge." For instance, when the 140-year-old railway overpass 'Simmerbach', located in Germany, was re-built using Preco-Beam technology, transport only had to be interrupted for a weekend.
Composite structures - in which different building materials are combined - gained prominence in Europe because of their high resource efficiency and low maintenance requirement. Yet, as European steel became less competitive compared to China's market, an innovative construction solution requiring less steel was needed. In order to meet this challenge, the Preco-Beam consortium brought together seven partners from France, Poland, Germany, Sweden, Belgium and Luxembourg .
"It's been a surprisingly fruitful working experience," Seidl says. "The international combination of partners meant we learnt from each other on a technical, as well as on a social level." With each of those seven partners contributing different aspects, the consortium was able to meet its goal of inventing a cost effective construction technology. Indeed, an analysis carried out for the Deutsche Bahn [Germany's national rail service], showed that using Preco-Beam in its bridges could have cut expenses by approximately 40 percent.
The project has been an important achievement for Europe as well, as it may increase the value of EU steel market shares, which could spread EU innovation across member states and beyond. To that end, the Preco-Beam consortium is already disseminating technical guidelines and design rules via the Internet, and there are plans to use Preco-Beam for buildings.
Meanwhile, European citizens may be more likely to enjoy the benefits of their infrastructure, now that inconveniences caused by construction have been reduced to a mere weekend.
Participants: Germany (Coordinator), Luxembourg, Belgium, Poland, France, Sweden
Project N° RFSR-CT-2006-00030
costs: € 1 396 401
contribution: € 837 941
36 months (July 2006- June 2009)
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