Advantages of moisture content monitoring in timber bridges

Timber road bridges are high performing structures and built worldwide since centuries. Modern timber bridges are designed for operational life cycle of 80 to 100 years. Reliable design and proper planning fundamentals, as well as the right choice of assessment method and monitoring systems, support the planning process and maintenance. The electrical resistance measurement method has proven to be suitable for the moisture content monitoring of timber bridges. The long-term monitoring of moisture content of structural components enables to react to discrepancies at an early stage of possible damage. The monitoring results of six timber bridges showed that the wood moisture content in the load bearing cross sections under regular ambient climates was between 12 M% - 22 M%, i.e. continuously below the range for fungi decay. Numerical methods were used to estimate the dependency of moisture content over the cross section on the yearly climate loads.