Are there any incentives to move towards lighter bridge structures? Is it possible?
Lighter structures can improve e.g. logistics by using less transportation, it can speed up constructability especially in urban areas. New materials can contribute to reduced maintenance intervals which in turn generates reduced disturbance into the built environment.
To investigate if it may be possible to design lighter structures, an alternative to an ordinary pre-tensioned concrete railway bridge with a ballasted track was developed. The overall bridge length is about 390m with individual spans of about 53m. The aim was to find a light and strong bearing structure using existing materials and available systems using existing codes. Eyes turned towards Biomimicry where the structure of a carbon nanotube was chosen. The tube was scaled to a diameter of 12.5 m and given the properties of a steel pipe. A bridge deck of concrete with embedded rail was integrated into the tube.
It was found that it was possible to reduce the weight by 50% by using the scaled nanotube and recent progress in computational mechanics using a systems approach for the bridge, the train and the track. Pushing the limits further and replacing the concrete bridge deck with a CFRP one would give a weight of 25% of the conventional bridge.
Participating partners are WSP Sweden AB, Vectura Consulting AB, Ruukki Sweden AB and &Rundquist Architects.
Johan Jonsson, Graduate Member in Sweden