Improving strength grading of lumber by grain angle measurement and mechanical modeling
TypeArticles dans des revues avec comité de lecture
Timber strength grading has become a major issue in the European Union during the last years, due to the introduction of the Eurocode 5 and all its related standards. Currently, the most performing strength grading machines are able to locally detect the boards’ knots sizes and positions and interpret this information through adapted grading models. The best lead to improve their accuracy seems to be the introduction of new information about the boards and adapt the mechanical model to take them in account. Small grain angle causes high reduction of clear wood’s mechanical properties, local value of slope of grain appears to be of high interest. The aim of this study is to quantify the additionalaccuracy that grain angle information can bring toan optical scanner used as a strength grading machine. A specific grading model has been developed accordingly, and the results obtained for different machine / model / loading combinations are presented. These results show that slope of grain measurement can significantly improve the accuracy of the optical scanner, for both MOE and MOR estimations.
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Modelling mechanical properties of spruce and Douglas fir timber by means of X-ray and grain angle measurements for strength grading purpose VIGUIER, Joffrey; BOURREAU, Damien; BOCQUET, Jean-François; POT, Guillaume; BLÉRON, Laurent; LANVIN, Jean-Denis (Springer, 2017)This study proposes a model using data from a scanner (X-ray and grain angle measurements) to perform strength grading. The research also includes global measurements of modulus of elasticity (obtained by vibrations and ...
BLERON, Laurent; DENAUD, Louis; COLLET, Robert; MARCHAL, Rémy (Lavoisier, 2011)Since the test method for compression strength perpendicular to the grain was changed from a partial area to a full area loading test, strength values for softwood in EN 338 were significantly reduced. Consequently, a ...
HANNOUZ, Simon; COLLET, Robert; BUTAUD, Jean-Claude; BLÉRON, Laurent; CANDELIER, Kévin ("PRO LIGNO" Foundation, 2015)Heat treatment is an attractive method to enhance wood durability, and valorize local hardwood species with natural low durability. Yet no standard allows the certification of such products. This study first aims to observe ...
ROBLOT, Guillaume; BLERON, Laurent; MOTHE, Frédéric; COLLET, Robert (Taylor & Francis, 2013)The settings of strength-grading machine for structural pieces of wood are checked according to the EN 14081 standard. However, different machines have different performances depending on the accuracy of the estimation of ...
Evaluation of the visual stress grading standard on French Spruce (Picea excelsa) and Douglas-fir (Pseudotsuga menziesii) sawn timber ROBLOT, Guillaume; COUDEGNAT, Damien; BLERON, Laurent; COLLET, Robert (EDP Sciences, 2008)In this paper an evaluation of the visual grading standard for softwood sawn timber was made. • In order to do so, visual grading according to EN 518 and theoretical grading according to EN 338 and EN 384 (measurements of ...