Rehabilitation of Illerkanal Viaduct at Kirchdorf - A Steel Composite - Precast Concrete Construction

摘要

Illerkanal Viaduct is located in Baden-Württemberg, Germany. The bridge on the A7 motorwayconnecting Ulm and Füssen crosses the Iller canal and two rural roads north of Memmingen atKirchdorf. The Iller canal feeds a hydroelectric power plant and could thus be closed onlytemporarily to demolish the existing superstructure while the substructures were reused to conserveresources. Due to the local and geographical situation, a steel composite deck was used to cross theIller canal forming the main span while precast concrete deck was used for the end spans.The relatively long center span was designed as a twin composite box girder, making it a relativelylight structure. To balance out the center span and avoid bearing lift-off at the abutments the endspans were designed as double T-beams in precast concrete.The basic idea for this arrangement was to move the point of zero moments towards the couplingjoint of composite and precast concrete structure, i.e. the composite section is connected directlywith a concrete cantilever thus is not supported directly by piers. In order to optimize steel platethickness, post-tension was varied, thus the points of zero moments could be moved further towardsthe middle of the bridge.This rarely used construction is a very innovative solution crossing a large span while having asolution for the resulting technical challenges.