Approaches to the moisture content monitoring in timber elements: Development of a resistive method

Abstract : The scope of this pilot study is based on the use of a resistive method to quantify the water content in timber elements for a monitoring approach. For an in-depth mapping, we adapted a multiplexed technique derived from geophysics based on a maximum crossing of current lines to obtain topography of measures sweeping the space boundary conditions being defined by the sample. The calibration of these measurements is completed by a gammadensimetry laboratory method which allows access to water profiles along a preferred direction. Nevertheless, the resistive method is penalized by logarithmic laws linking moisture and resistivity. So, we develop a hybrid method for coupling the data obtained to diffusion models: it will provide complementary information where resistivity and gammadensimetry are no longer effective. The developed experimental protocol allows employing the selected method and optimizing the diffusion properties (diffusion coefficient and convective exchange coefficient) injected into a characterization algorithm (Nelder-Mead's simplex inversion method) based on a finite difference method for the Fick's diffusion law determination integrating orthotropic and non- linear properties. Overlaps between electric field and density measurements and the numerical simulation tool are possible