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Properties of clear wood and structural timber of Pinus halepensis fromnorth-eastern spain INCAFUST

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Properties of clear wood and structural timber of Pinus halepensis fromnorth-eastern spain INCAFUST

  1. 1. Properties of clear wood and structural timber of from north-eastern spainPinus halepensis Eduard Correal-Mòdol - Marcel Vilches Casals INSTITUT CATALÀ DE LA FUSTA - CATALAN INSTITUTE OF WOOD Headquarters: Ctra. Sant Llorenç, km.2 - 25280 Solsona. T. 973 484232 - F. 973484231 - @incafust Introduction TheAleppo pine ( ) is a tree species spread all around the Mediterranean basin including the islands. It grows mostly from sea level to 1.000 m. In Spain is most abundant from 200 m to 600 m because lower altitudes are occupied by crops or urbanized areas. It is a xerophilous and heliofilous species with little and irregular annual growth. The biggest trees may reach 50 cm of diameter and 20 m height but they usually don't get over 40 cm and 15m. The stem it is not very straight, large branches are common, therefore has low quality. It has an average growth of 2.4 m /ha/yr. The Aleppo Pine nowadays in Spain it is mainly being used by the packaging industry for producing pallets. However, traditionally round trunks were used as beams in isolated houses located nearby the forests, especially in the Mediterranean coast where it is the most abundant tree. The goal of the study was to characterize the physical, mechanical and structural properties for knowing the potential of the Aleppo pine for building. This is quite relevant because nowadays is widely believed that Aleppo pine timber is not suitable for structural use despite its beams are found in ancient buildings. Pinus halepensis 3 Table 1. Physical and mechanical clear wood properties Figure 1. World distribution of (Bioversity International, 2011)Pinus halepensis Materials and methods The study is divided in two: characterization of clear wood and characterization of structural timber. The timber used in the experiment came from the region of provenance “Catalunya interior”. 100 beams were from the “Serra de Prades” (Tarragona) and they had nominal dimensions of 50×150×2850 mm. There were other 81 smaller beams from “Prats de Lluçanes” (Barcelona) with nominal dimensions of 45×110×2000 mm. 68 beams of Aleppo Pine from “Serra de Prades” and “El Lluçanès” were accepted after being visually graded according to the criteria of UNE-EN 14081-1:2006+A1 and UNE 56544:2007. Clear wood test samples were made according to UNE 56528:1978 (AENOR, 1978) and afterwards conditioned at 20ºC and 65% of relative air humidity until they reached 12% of moisture content. Figure 2. Clear wood sample on the bending test Results: Clear wood properties The Aleppo pine clear wood is slightly denser, harder, and has more bending and compression strength than the other most common pines grown in Spain as a source of timber. However, the reaction to moisture is more unstable because it has more shrinkage. (Table 1). Results: Mechanical characterization The 77% of the beams were rejected on the visual grading. The batch of “Serra de Prades” was entirely rejected because big knots and large deformations, however 41 beams of the batch of "El Lluçanès" were classified as ME-2-like specimens. Unfortunately there were very few ME-1. The Aleppo pine ME-2-like timber is relatively stiff and heavy comparing it with its loading capacity. The MOR is what limits the strength class to C14. The cause of this behaviour is the high incidence of the defects on the resistance. The Aleppo pine demonstrated a far lower strength class than the Spanish species that already have a visual grading norm: C18 vs C14 (UNE 56544). The beams don't crunch or crack much during the load because the timber is rigid, but the breakings are sudden and violent and all the energy is released at once. Most beams resulted seriously damaged when broke. This behaviour is probably due to the material can't much cope with plastic strain.(Table 2). Conclusions The clear wood of has better resistance than other Spanish coniferous used in timber structures. However there is little difference. Unfortunately the timber has a low quality and a lot of rejection. Thus, it is necessary to invest on silvicultural works. The Aleppo Pine from North- eastern Spain (Catalonia) is the native pine timber with the lowest load capacity. The timber visually graded according to the criteria of the ME-2 class on the UNE 56544:2007 might be considered C14. Only one quality strength class should be purposed for this species if included on a visual grading norm. On one hand, the high quality timber is rare, and on the other, it will ensure at least a C14 strength class when including also the best samples on a unique batch. Pinus halepensis ME-2-like Rejected 41 27 25.34 18.88 Sn-1 3.86 6.96 P5 18.76 8.77 Ch. Value 13.62 6.37 10,718.39 10,285.56 Sn-1 1,150.35 1,797.28 P5 8,901.50 8,168.56 Ch. Value 8,777.27 8,422.83 611.47 580.79 Sn-1 40.29 37.28 P5 575.24 513.65 Ch. Value 679.42 606.67 C14 RejectedStrength class Property Beams tested MOR (N/mm 2 ) MOE (N/mm 2 ) Density (kg/m 3 ) x x x Property Sn-1 Density (kg/m 3 ) 589.91 55.01 Shrinkage (%) 14.13 2.33 Shrinkage coefficient (%) 0.45 0.072 Higroscopicity (kg/m 3 ) 0.0032 0.0004 Hardness (mm -1 ) 4.26 1.22 Axial compressive strength (kg/cm2 ) 594.91 76.57 Bending strength (kg/cm 2 ) 1,106.82 175.23 x Table 2. Visually graded timber: MOR, MOE and density ! ! ! ! ! ! ! ! ! ! !! !! ! ! ! ! !! !! ! ! ! ! ! ! ! ! ! ! ! ! ! !!! !!! ! ! !!!!!! ! !!!! ! ! !!! ! ! ! ! ! ! ! !! ! !! ! ! !!!! !!! ! ! ! ! ! ! ! ! ! !!!!!! !!!!!!!!! ! !!!!!!!!! !!! !!!!!!!! !!!! !!!!! !!!!!!!!!!!!!!!! !!!!!!!!!! ! !! ! ! !!! ! !!!!!! !! !!!!! ! !!! ! !!!!! !! ! !!!!!!!!!!!! !!!! !!! !!!!!!!! !!! !!!! ! !!! 40°E30°E20°E0°10°W 10°E 40°N 30°N 0 500 1,000250 Km Figure 3. Shattered beam of Aleppo pine on bending test Figure 3. Shattered beam of Aleppo pine on bending test