Wooden bridge Sihlmatt, Hirzel

The project
The wooden bridge over the Sihl was built in the years 1849 - 1850. It was a central connection of the main traffic axes between Lake Zug and Lake Zurich. In 1960 it was moved upstream to make room for a new, larger bridge at the old location. Now the wooden bridge is mainly used by hikers and the directly surrounding farms. Timbatec Holzbauingenieure AG was commissioned by the Civil Engineering Office of the Canton of Zurich to carry out a condition survey of the wooden bridge. It was found that some components of the supporting structure were almost completely decayed due to insect infestation. A renovation of the bridge was therefore absolutely necessary.

The construction
The repair project was carried out in close cooperation with the Civil Engineering Office of the Canton of Zurich and the preservation of historical monuments. A team consisting of the carpentry firm Schneider GmbH and the hydraulic engineers Willi Stäubli Ing. AG was formed to repair the damaged components. In order for the bridge to meet all safety requirements again for the coming years, the damaged parts were replaced. In addition, the structural wood protection was improved.

The challenge
Due to the construction method, it was a great challenge to replace the components without dismantling the bridge into its individual parts. By means of temporary driven piles in the watercourse, the individual components could be carefully replaced without dismantling the bridge. The rehabilitation was successfully completed thanks to the good cooperation of all parties involved.