Non destructive evaluation of timber structures using GPR technique

This paper deals with the study of the GPR technique for timber structures evaluation. According to the electromagnetic (EM) theory, GPR wave´s propagation is governed by the EM properties of a dielectric material as wood, which is affected by various parameters such as moisture, as well as heterogeneities. This paper presents some laboratory measurements in the aim of studying the sensitivity of electromagnetic waves to moisture variation in wood material. Dielectric relative permittivity was measured using resonance technique at 1.26 GHz for Spruce and Pine wood samples. GPR measurements were also carried out using GSSI SIR 3000 system connected to 1.5 GHz antennas on several wood samples. The results of this study show the good relations between real/imaginary relative permittivity and moisture content of the different wood samples. Moreover, due to the dependence of wood permittivity to moisture, GPR features in time domains present some correlations with moisture content of wood material.