The Egg-Graben Bridge in the Grossarl Valley (Salzburg) was designed and planned at the Vienna University of Technology. FIB, the international umbrella organization for concrete construction, recently named the Egg-Graben Bridge as one of only two bridges worldwide to receive the “fib Award for Outstanding Structures”. The prize will be bestowed in 2014 at the fib conference to be held in Mumbai, India.
The award is only given every four years. This time around Austria will be given the “Concrete Oscar“. The award-winning Egg-Graben Bridge was designed and planned at the Vienna University of Technology. The bridge is aesthetically appealing thanks to its particularly streamlined shape. Technologically speaking the bridge is also a masterpiece. It was constructed in accordance with a newly developed bridge construction technology. In comparison with other bridges, there is no danger that the steel components within the concrete will be subject to corrosion. Thus the maintenance costs are significantly lower.
Corrosion as a bridge killer
Johann Kollegger and his team at the Institute for Structural Engineering at the Vienna University of Technology already repeatedly aroused considerable international attention in past years due to their exotic ideas, for example the new type of bascule bridge process. Now a bridge construction method has been developed to enable bridges to be much more weather resistant. “Normally concrete bridges are reinforced with steel”, Kollegger explains. “Therefore the bridge must be re-sealed on top. Otherwise water and salt will get inside, corrode the steel reinforcement and endanger the stability of the bridge”, he adds.
Steel cables in a plastic covering
Instead of the steel reinforcement, only a few strong tendons are poured into the concrete of the bridge i.e. several particularly strong steel cables with a diameter of 16 mm. The tendons are packed in a plastic covering and then poured into the concrete. As a result, they cannot be damaged by any salt water which gets inside. Moreover, any potential damage to the steel can be determined on the basis of a simple electrical resistance measurement in the steel. The carriageway is longitudinally and transversely pre-stressed. The strong tendons pull the bridge components together and make them resilient to external forces.