Alessandra Genoese

FEM simulation of the hygro-thermal behaviour of wood under surface densification at high temperature

Surface densification of solid wood increases the density on the surface, when compressed by single side heated press. A recent experimental study has pointed out the influence of the process parameters on the development of the density profiles in the modified samples. Numerical modelling can help to optimize the experimental work which is often time consuming and laborious due to the large amount of experiments required to check the influence of the pressing parameters. In the present work, a FEM simulation of the hygro-thermal behaviour of wood under surface densification is proposed by using a three-dimensional hygro-thermal model based on earlier literature approaches. The model is implemented in a user subroutine of the FEM code Abaqus starting from the definition of a weak form of the governing hygro-thermal equations of the problem. The numerical profiles of moisture content and temperature during the wood densification process are simulated for some wood specimens tested in a previous study. Conclusions are given on the relationship between these profiles and the experimental density profiles due to different process parameters.

A Numerical Approach for the Hygro-Thermal Monitoring of Timber Structures under Environmental Conditions

The monitoring of timber structures exposed to natural climate fluctuations during their service life is an important topic for both their serviceability and safety. Numerical methods based on the recent advances in hygro-thermal modelling of wood can integrate the usual sensor-based monitoring techniques by reducing the maintenance costs for timber structures. In this paper, a 3D full coupled analysis based on the multi-Fickian theory with sorption hysteresis of wood is implemented in Abaqus FEM code by defining a new finite element in a user subroutine. To verify the method, the hygro-thermal behaviour of a glulam beam tested in laboratory under variable humidity within a previous research is analysed and the numerical values of moisture content are found to be in agreement with the experimental data. Furthermore, a numerical case-study of a glulam cross section under real climate variations is presented and the related results show the capability of the method to predict the moisture states in each points of the glulam member under continuously variable humidity and temperature.