Design and performance prediction of timber bridges based on a factorization approach

Service life of timber bridges is predominantly affected by the site-specific climatic conditions in terms of moisture and temperature over time, the overall design, the design of details, and the choice of materials. In recent years, a performance-based methodology has been developed to predict (1) the material climatic conditions within timber components from macro climate data and comparison between design details, (2) decay intensity from material climate data, and (3) the material resistance as a combined effect of wood-inherent properties and its moisture dynamics. Within the WoodWisdomNet project Durable Timber Bridges' we emphasized on utilizing exposure, decay, and resistance models for a comprehensive guideline for the design of timber bridges. Therefore, a factorization approach is presented based on dose-response relationship between wood material climate and responding fungal decay. The concept does also allow for quantifying the material resistance of untreated, modified, and preservative-treated wood using factors based on laboratory and field durability tests and short-term tests for capillary water uptake, adsorption, and desorption dynamics. The findings from the present study have the potential to serve as an instrument for design and service life prediction of timber structures and will be implemented in an engineering design guideline for timber bridges.