Strengthening of an old Arch Truss Bridge, Austria

In 1889, a railway line was built in Lower Austria as a connection of the two main lines, Vienna to Prague and Vienna to Krems. In the narrow valley this line had to cross the river five times, which was at that time an unregulated and wild river. Five skewed single-track steel bridges with parabolic truss girders were designed for the second load class of that time. The importance of this line decreased after World War One until the opening of the iron curtain in 1989, and for decades the railway was used by commuter trains only. Today, enterprises are again interested in transporting their goods by train, particularly wood. The Austrian Federal Railways decided to reinforce the line. Two of the five bridges were replaced by new girder bridges, two by new truss bridges and one bridge, which was in the best condition and in historic surroundings could be strengthened. This paper deals with this strengthening. All five bridges withstood the disastrous flood of the river Kamp in August 2002 without damage due to their special foundations. However, the railway line was severely damaged.