Steel and composite bridges – Enabling sustainable solutions

Sustainable bridges are characterised by three main aspects: saving resources by an efficient construction, allowing for a lifelong use of bridges by optimal detailing in view of fatigue and flexible design concepts for strengthening and adapting to changed user requirements. After a short introduction in the assessment of sustainability for bridges, an overview on recent bridge research in view of sustainability is given. The key point of efficient construction in future is the use of high strength steel (HSS): basic research and adaptation of rules are needed for welding of matching and mismatching connections. Joints and their relevant failure modes are to be investigated before hollow sections of HSS can be used in a wider range. And for steel and composite bridges, optimised plate buckling rules may serve for more efficiency in construction. Bridges are designed for a service life of 100 years. This can easily be achieved and even exceeded if the detailing is realised in view of fatigue. Research on welded details such as butt welds or joints of tubular bracings will be presented. Welds can be improved by post‐weld treatment such as high‐frequency mechanical impact (HFMI) treatment. Fatigue is also a key issue when steel and concrete or timber and concrete are combined for composite bridges. Reinforced composite slabs without prestressing require a fatigue verification for the transverse shear also in areas with cracked concrete. The notch forms an efficient connection in timber‐concrete composite (TCC) bridges, where, however, little has been known up to now on the fatigue behaviour.