The Turkish Osman Gazi suspension bridge is visible in the background and the topology optimisation result in the top right. Subsequently, the result of the optimisation – organic in appearance and highly complex – was interpreted, which led to a new, simpler design (marked in red). Compared to the conventional design (marked in blue), the new design entails weight savings of more than 28 per cent for the bridge girder. The white arrows indicate the course of the design process.
The computer calculation presented input for how to best structure the design space of the bridge deck. Among other things, that meant curving part of the currently straight transverse diaphragms, making it possible to shave off 28 per cent of the material that is used for bridge decks. Thereby, you achieve a corresponding reduction of the CO₂ emissions generated by the production and transport of concrete and steel.
“We adjusted calculations to ensure that the bridge girder structure has the optimum design, and that it can be carried out without too costly production methods. The economic aspect is important in order for the design to be a realistic option for future bridge projects,” says Mads Jacob Baandrup.
Naturally, additional analyses will be required before the new design can be used for building bridges, but COWI is confident that the results of the research project add valuable knowledge to tomorrow’s suspension bridges.
“The new bridge girder design can be converted into a weight and CO₂ reduction of up to 20 per cent for the entire bridge, which of course benefits the climate. COWI is also involved in a wide range of the world’s largest bridge projects, so a potential new design will also benefit our customers and society,” says Technical Director Henrik Polk, COWI, who participated in the research.
DTU is also very excited about the results.
”We believe there are huge perspectives to using topology optimisation for ensuring sustainable design of other large building structures, such as high-rises, stadiums or highway bridges. We want to explore that field, and since the construction industry accounts for 39 per cent of global CO₂ emissions, almost any reduction can be of interest,” says Professor Ole Sigmund, DTU Mechanical Engineering.