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 and the design of details. In particular if bridge builders abstain from use of wood preservatives smart and effective design solutions are needed and their effect on durability needs to be determined in a reliable and quantitative way. In recent years a performance based methodology have 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 combined effect of wood-inherent properties and its moisture dynamics. Within the WWN project ‘Durable Timber Bridges’ we emphasized on utilizing exposure, decay and resistance models for a comprehensive guideline for design of timber bridges. Therefore, a factorization approach is presented based on dose-response relationship between wood material climate and responding fungal decay, where onset of decay is defined as limit state. 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. According to the principle of ‘relative performance’ relevant timber bridge details were compared after moisture and temperature monitoring of real-size components in long-term outdoor exposure. The findings from this study have the potential to serve as instrument for design and service life prediction of timber structures and will be implemented in an engineering design guideline for timber bridges.
Keywords: Decay modelling, glulam, moisture risk, Network arch bridge, Norway spruce
Authors
Brischke C.
University Goettingen, Faculty of Forest Sciences and Forest Ecology, Department of Wood Biology and Wood Products, Goettingen, Germany
Meyer-Veltrup L.
Leibniz University Hannover, Faculty of Architecture and Landscape Sciences, Institute of Vocational Sciences in the Building Trade, Hannover, Germany
Niklewski J.
Lund University, Division of Structural Engineering, Lund, Sweden
Thelandersson S.
Lund University, Division of Structural Engineering, Lund, Sweden
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