Ermüdungsverhalten geschweißter Rohrknoten von Fachwerkverbundbrücken

Fatigue behaviour of welded pipe intersections in steel-concrete composite bridges.

In the construction of modern steel-concrete composite bridges, the steel part is increasingly built by circular hollow sections instead of steel plates. This type of bridge design shows advantageous characteristics concerning architectural aspects as well as benefits in the static load transfer. Especially if the design of the truss girder requires a large number of different node geometries, the connection between the braces and the lower and upper chord are for economic reasons preferably build by directly welded nodes instead of cast steel nodes. Due to the local joint discontinuity of the pipe intersections, the stress distribution is enhanced exactly in the area of the welding seams. As a consequence, the limited fatigue behaviour of the pipe intersections represents the critical aspect in the design of tubular truss-girder bridges. The difficulties in the design of this construction type are due to the fact that the criterions for fatigue verification given in the current codes do not cover the typical dimensions used in bridge design. Therefore until now it is unavoidable to conduct large-scale tests in order to verify a sufficient fatigue resistance. This article refers to a total of seven specimens tested on fatigue during the construction of the new Highway Overpass Suhl- Lichtenfels.