CLAMEB

Wood is a material that must contribute to achieving the European objectives fixed by 2020 in terms of sustainability, environmental quality buildings, (20 % reduction in consumption), energy saving materials and renewable fuels (20 %) and especially against climate change (20 % reduction of greenhouse gas emissions) usage. No other traditional construction material has these qualities. In France, it has been also highlighted all the interest which represents a larger utilization of timber in the construction industry. For these reasons, the development of the use of wood in the building is worn by a political will of the European Union and the States. In order to allow a homogenization of wood structures sizing methods, European codes (Eurocode 5 in the case of timber) permanently replace national rules from 1 March 2010. However the Eurocode 5 obliges prescribers to use wood which has been classified visually or mechanically. Processes and standards of classification, mainly developed by the leading Northern European countries are not adapted to deliver the highest value for the French softwood species. The challenge is first to acquire the knowledge necessary to classify optimally the sawn from the national resource, i.e. without downgrade them. This project focuses primarily on the douglas fir which harvest availability will be very important in the coming years, but also discusses the spruce, fir, oak and will lead to development of a methodology that can then be applied to other species. According to standard EN 338, the classification of a lumber requires to assess its density, its Young modulus, its bending strength (MOR), and to compare them to the limits defined by the standard and then to infer the resistance class. The non-destructively MOR estimate is the main technological lock. The accuracy of the assessment of the MOR by current machines remains little accurate. This is why we want to improve the effectiveness of these methods by adding several parameters such as wire slope, water content or wood compression. The development of classification machines that are more reliable and more efficient than the visual ranking, which can reach industrial rates and remain in reasonable price scales represents a very important issue. There are already optical or x-ray scanners to obtain information about the nodes or local density, but many optimizations remain to be carried out by a detailed analysis. There are a number of machines in the market but their prices are too expensive for small or medium-sized structures which will never be able to finance such systems. Demand is strong and in France mainly, since as a significant amount of softwood planted in the after war is currently to be mature. The visual classification limits the utilisation of these wooden structures for building parts although they have very good mechanical characteristics. An alternative to visual ranking is therefore imperative to get the most from these wood. It is essential to conduct an ambitious research program in France in this area to control measuring parameters and their treatment to predict more accurately actual mechanical skills of the wood to optimize the most this material.