The Ortho-Composite-Slab of the Elbebridge Wittenberge

The main Bridge of the Elbebridge Wittenberge is a 3-span continuous beam steel bridge with a wave-like curved upper chord between the two carriageways. With spans of 126 - 160 - 126m and a slenderness of 32, the superstructure requires a light but fatigue resistant roadway slab. These requirements are fulfilled by an “ortho-composite” slab which consists of a reduced orthotropic steel deck and a 15cm thin in-situ concrete layer, connected by shear studs. The advantages of the ortho-composite slab compared to orthotropic steel decks are; the reduction of steel and welding effort, a much better fatigue resistance and no hazard of freezing rain. Compared to standard reinforced concrete slabs on steel girders, troughs or boxes, it is much lighter, easier and faster to build and gives a better stability during construction stages. As this construction type is not covered by German DIN-codes and German road authority contract conditions a single case approval is necessary. Large scale construction type tests have been performed for FLS, SLS and ULS truck loads. Additionally extensive FEM calculations have been carried out. The results show a massive reduction of stresses in the steel members compared to standard orthotropic steel decks and a huge load bearing reserve. All-in-all the ortho-composite-slab has proven to be the most economic and sustainable construction type for the Elbebridge Wittenberge.