Joris Van Acker: Fit for purpose selection of wood materials

Abstract: Wood is worldwide applied for many end uses. Some construction related applications require extra attention related to service life. The role of inherent wood durability of wood species and their origin as well as option to enhance both durability as moisture dynamics allow the wood industry to provide a range of product types and performance levels. This variability in properties from biological origin in combination with man-made transformations allows the end user to select from a range of alternatives to accomplish fit for purpose criteria defined by limit states. These have been identified as simple classification systems in the past but are now evolving toward model based approaches combining resistance to biological degradation and moisture dynamics.
European standardization within CEN TC 38 on wood durability is working on this topic and test methodology as well as decision support mechanisms are under discussion. Meanwhile also the forum on how to enhance wood properties is working on this renewed concept, e.g. the International Research Group on Wood Protection (IRGWP) and the European Conference on Wood Modification (ECWM). Although the approach to match performance of wood products with material characteristics seems straightforward several additional parameters seem to interact and require additional stochastic modelling related to different commodities, overall and local climate, design, biological hazard, presence and probability of decay organisms, time of wetness, etc.
Extra tools are being developed to understand such parameters. State of the art assessment of moisture content (e.g. continuous moisture measurements), structural impact at microscale using CT scanning, NIR tools to verify presence of active components, advanced method to detect wood rot are all part of new methodology to predict service life of wood based products in general and in particular as construction component, e.g. new engineered wood products like CLT. This paper intends to propose a fit for purpose flow chart for decision making related to parameters defining material characteristics of these wood based products as well as present different state-of-the –art tools available to assist in assessing such parameters.