Re-writing the rule book on bridge design, using 19th century maths

YORKSHIRE RESEARCHERS are re-writing the rule book when it comes to building bridges – which could lead to longer bridge spans in future, potentially enabling engineers to build a structure that could cross the Strait of Gibraltar.

University of Sheffield academics, working with researchers from Brunel University London, and engineering consultants COWI, have used a new mathematical modelling technique to identify optimal forms for very long-span bridges.

The current world record for a bridge is just under 2km, with the most popular form for long span being the suspension bridge, as used for Humber Bridge.

However, as bridge spans become longer, a rapidly growing proportion of the structure is needed just to carry the bridge’s own weight, which can create a vicious cycle of relatively small increases in span needing significantly more material, leading to a heavier structure. The team’s new design, incorporating 19th century mathematical theory, changes the shape of suspension cables to allow them to take greater loads.

The new concept, which has spokes resembling a bicycle wheel, has identified the minimum possible volume of material need for the bridge to support itself, potentially making significantly longer spans feasible.

Professor Matthew Gilbert from the University of Sheffield, who led the research, said researchers had “never stopped to look” to see the suspension model was actually the best form to use.

“Our research has shown that more structurally efficient forms do exist, which might open the door to significantly longer bridge spans in the future.”