Visual grading criteria for Japanese larch ( Larix kaempferi ) structural timber from Spain
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ORIGINAL PAPER
Visual grading criteria for Japanese larch (Larix kaempferi) structural timber from Spain Mari‑Jose Barriola1 · José‑Ramón Aira2 · Edgar Lafuente3
Received: 28 November 2018 / Accepted: 4 January 2019 © Northeast Forestry University 2019
Abstract Larch wood is structurally classified in many countries as one of conifers with the highest load-bearing capacity (strength class of C30). The Spanish visual classification regulation only assigns a strength class to 4 pine woods: Laricio pine (Pinus nigra Arn. var. Salzmannii), Silvestre pine (Pinus sylvestris L.), Radiata pine (Pinus radiata D. Don), and Pinaster pine (Pinus pinaster Ait.). This work adds to the number of structurally characterised species by creating a visual classification table for Japanese larch wood (Larix kaempferi (Lamb.) Carr.) which differentiates between 2 visual classes, MEG-1 and MEG-2. Characteristic strength values were calculated for each class (fk,MEG-1 = 31.80 MPa, fk,MEG-2 = 24.55 MPa), mean module of elasticity (E 0,mean,MEG-1 = 13,082 MPA, E 0,mean,MEG-2 = 12,320 MPA) and density (ρk,MEG-1 = 456.6 kg m−3, ρk,MEG-2 = 469.1 kg m−3), before finally assigning a strength class of C30 to visual class MEG-1, and a strength class of C24 to visual class MEG-2. Project funding: The project has been funded by Basque centre of research and applied innovation in vet (TKNIKA). The online version is available at http://www.springerlink.com Corresponding editor: Yu Lei. * José‑Ramón Aira [email protected] 1
Tknika, LHri Aplikatutako Ikerketa eta Berrikuntzako EAEko zentroa, Zamalbide Auzoa z/g, 20100 Errenteria, Gipuzkoa, Spain
2
Escuela de Ingeniería de la Industria Forestal, Agronómica y de la Bioenergía, Universidad de Valladolid, UVa‑Campus Duques de Soria, s/n, 42005 Soria, Spain
3
Cesefor, Centro de Servicios y Promoción Forestal y de su Industria de Castilla y León, Calle C, 42005 Soria, Spain
Keywords Japanese larch wood · Visual grading · Strength class · Mechanical properties · Density
Introduction Each country has developed national standards for structurally classifying wood from its forest stands, establishing its own structural classification and nomenclature. Due to the great variety of wood species, origins and different classification rules, it is recommended to use the European structural timber grading system. This system is set out by the harmonised standards EN 14,081-1:2016, EN 14,0812:2018, EN 14,081-3:2012 +A1:2018, and supporting standards. Rectangular cross-section timber is classified into categories (strength classes) according to three key properties: strength, stiffness and density. The strength classes and their properties are shown in standard EN 338:2016. There are two systems for structural timber grading, visual grading and machine grading. Visual grading consists of measuring the singularities of wood, which affect its strength and stiffness, such as knots, slope of grain, width of growth rings, pith, cracks and so on. The number of classes into which one can grade is
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