NON-DESTRUCTIVE EVALUATION OF THE MECHANICAL BEHAVIOR OF CHESTNUT WOOD IN TENSION AND COMPRESSION PARALLEL TO GRAIN

This article addresses the evaluation of the strength and stiffness of chestnut wood, in tension and compression parallel to the grain, using different non-destructive techniques (ultrasounds, Resistograph(R) and Pilodyn 6J). Approximately 200 timber specimens (divided into compression and tension tests) were tested up to failure, comprising recently sawn timber (which is now available on the market for structural purposes) and what was called old wood, obtained from structural elements belonging to ancient buildings. The possibility of predicting wood properties by application of non-destructive techniques is discussed based on simple linear regression models. Extrapolation of regression models obtained from recent cut wooden material to that obtained from old timber beams is analyzed. The results show reasonable correlations between mechanical elastic properties and non-destructive techniques (ultrasounds, Resistograph(R) and Pilodyn 6J). New and old wood mechanical data exhibited a scattered cloud of points, implying in terms of assessment of properties of timber elements in service by regression models that these models should not be supported only on data from recently sawn wood. Therefore, models combining information from new and old wood specimens are proposed based on lower 95% confidence limits of regression lines.