Planung der Hochstraße BAB A 281 (Bremen) in Stahlverbundbauweise mit Luftdicht Verschweißten Kästen

An elevated highway stretching over more than 1.1km forms the central element of the new Autobahn BAB A 281 along the outskirts of the Hansestadt of Bremen. The bridge structure 8W 2210 which was built between beginning of 2004 and end of 2007 is characterised by a steel-composite superstructure utilising multiple longitudinal airtight steel box girders. The overall structural system is divided into three sections, two approaches with a typical span length of up to 36.50 m and one central cable-stayed section with a 127 m main span. BW 2210 is presumably the last major bridge in Germany being designed and built on the basis of the old safety concept and the previous guideline for steel-composite girders as well as the codes DIN 18800 (03.81), DIN 1045 (07.88) and DIN 4227 (07.88). However, all statements and conclusions derived in the following are generally applicable to the new generation of German codes and regulations, too. Detailed and construction design particularly for steel-composite bridges requires at an early stage to define in detail both the erection method and the construction sequence (including the corresponding time schedule). In addition, a realistic assumption of the structural stiffness as well as an appropriate numerical modelling including all relevant construction stages is of essential importance. This particularly applies to a slender, wide and geometrically complex superstructure with multiple longitudinal girders as BW 2210. The precise prediction of the superstructure deflection is a central point in the structural calculations, since these values can not be determined "on the safe side". The pre-calculated deflection values represent an important basis for monitoring and control of the entire erection and pouring process and ultimately determine the achievable accuracy of the vertical bridge deck alignment. Furthermore a continuous and close coordination and cooperation between design, works preparation and construction is necessary in order to attain an optimised solution in terms of technical and economical aspects as well as time of construction, durability and thus overall quality of the bridge structure.