The main supporting structure consists of a roadway support, one or several pylons and steel anchoring. The pylons are made from timber or steel and are back-anchored in the roadway support or separately. The anchoring on the roadway supports replace the supporting structures and allow for particularly high span widths. The roadway supports generally consist of block-bonded laminated timber and can run on either a single-axis or curved double-axis basis.
Structural timber protection is the key to the longevity of a timber bridge. Structural timber protection intends for all structural timber components to be completely protected. In this respect, the following steps are taken into consideration: Installation of technically dried timber with a timber humidity of 12% in order to prevent insect infestation, protection against weathering, ingress of moisture, UV rays due to the installation of projections and skirting in the design as well as good air circulation to encourage drying out. Constructions designed in this way satisfy the requirements of protected timber bridges pursuant to DIN EN 1995-2 NA. This means that loss events are prevented and maintenance costs are minimised, and the use of timber preserving chemicals can be reduced and/or avoided. Structures protected according to DIN EN 1995-2 have a service life of 60 - 80 years*.
* Source: Redemption amounts calculation regulations - ABBV, BMVBS, status 2010 and study of DGfH 2006
Here is a selection of pylon bridges with timber supporting structures.