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Service life monitoring

For the long term due to structural timber protection

For the long term due to structural timber protection.
Bridges are one of the most important parts of our infrastructure and have to satisfy a wide variety of requirements – in all cases, however, their role is to overcome obstacles and to guide users safely over rivers, roads, cuttings, and so on. If a bridge is no longer usable, this usually has a far reaching impact on the local infrastructure. It is therefore a good idea to design bridges so that a long service life can be guaranteed for them and so that the bridge can fulfil its function for a long time.

The basis for the monitoring of the service life of bridges in Germany is provided by the calculation regulations on redemption sums (ABBV) of the Federal Ministry of Transport, Building and Urban Development. These define the service lives and maintenance costs that can be expected for different types of bridge in relation to the materials and design. Since 2010, for timber bridges designed with structural protection, an expected service life of 60 years with maintenance costs of 2% of the construction costs is estimated.

Historic bridges made from timber demonstrate that a far longer service life than this can be achieved with timber bridges, however. Examples like the Chapel Bridge in Lucerne or the Rhine Bridge in Badsäckingen show that timber bridges can last for several centuries. The special attribute of these bridges is that the supporting structure is always protected by a roof or casing – this is the principle of structural timber protection which, in turn, is also our principle for the planning of new timber bridges.

Research (table below) by the German Society for Timber Research e.V. (DGfH) show that bridges with structural timber protection can have a theoretical service life of 80 years with maintenance costs of 1.3%.

Our experiences show that a service life of over 80 years can be realised with modern knowledge of structural timber protection. The theoretical useful life of unprotected bridges can be considerably less than 30 years, which is why we do not ever recommend constructing unprotected timber bridges.