FEM simulation of moisture transport and evaluation of decay rating in untreated and thermally modified wood products

Wooden products exposed to variable climates are strongly affected by the levels of moisture content (MC) in the material. Under favourable temperatures and MC close to the fibre saturation point (FSP) of wood, or higher, the decay is a serious risk for the durability of wooden components directly exposed to the rain. In this context, numerical models able to simulate the moisture transport in all locations of a wood component is important to assist the existing sensor-based techniques. Earlier studies have shown that the single-phase (or single-Fickian) finite element modelling (FEM) of moisture diffusion in untreated wood is an efficient tool to simulate the moisture transport in wooden components of buildings sheltered from rain (Fragiacomo et al. 2011). To model the effect of rain, single-phase models with assigned water content on the boundaries can be found in the recent literature (Niklewski and Fredriksson 2019). In addition, the decay models are found necessary for the service life prediction and performance classification of wooden components (Brischke and Meyer-Veltrup 2016). Coupling between moisture transport and decay models can be useful for the assessment of durability in wood products and timber structures.