To obtain more detailed information on the effects of lignin and hemicellulose on the thermal-softening properties of water-swollen wood, we investigated the dynamic viscoelastic properties of Japanese cucumber tree specimens from which lignin or hemicellulose had been extracted. The specimens had different weight loss rates. Their dynamic viscoelastic properties were measured in the temperature range from 5 to 95°C. The value of E' decreased markedly with increasing weight loss rate in every treatment. The peak temperatures of tan δ for the lignin-extracted specimens were significantly shifted to lower temperatures as the weight loss rate increased. On the other hand, tanδ of the hemicellulose-extracted specimens was shifted to higher temperatures after it remained unchanged at first. When we take wood structure and the mechanisms of these treatments into consideration, the above results might suggest that the thermal-softening property of water-swollen wood, especially its thermal-softening temperature, is more greatly affected by changes in quantity and quality of lignin than by those of hemicellulose.

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In order to quantitatively analyze the environmental impact of wood pellets produced in Hokkaido, we carried out a life cycle impact assessment using LIME2. The external cost of the pellets was estimated at 1461 yen/t, and the impact of CO₂ emissions on global warming accounted for 45% of the cost. The production process of the pellets has the highest CO₂ emissions in the life cycle, and thus improvement of productivity in the process is important for reduction of the impact. In a comparison of life cycle impact among 5 heating systems, the external cost of the pellet stove heating system was smallest, since the combustion of wood is regarded as carbon-neutral. CO₂ emissions could be reduced to the range of 753 to 5642 kg/household/year, if the pellet stove heating system was introduced to general households in Hokkaido. For example, introducing that system as an alternative for the kerosene stove heating system would reduce CO₂ emissions by 43% per household a year.

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In the latest articles, the strength of bolted connections loaded perpendicular to the grain have been studied with fracture mechanics. To estimate the strength of such connections, we need some material properties, e.g., fracture toughness and bending strength perpendicular to the grain (the properties used in the previours papers). However, the test method for bending strength was not described, and the number of test samples was insufficient. Therefore, evaluation of the data for construction design and establishment of a database is important. In this study, we conducted CT tests, three-point bending tests for the strength perpendicular to the grain and block shear tests. Additionally we analyzed the data by statistical methods. As a result, the 5% lowest value based on two-parameter Weibull distribution with 15% of the lower data is the lowet of all statistical methods. The 5% lowest value based on the normal distribution and the two-parameter Weibull distribution with 15% of the lower data, and the 5th percentile value based on ISO13910 are lower by all methods. Next the average value and standard deviation of mode1 fracture toughness and bending strength perpendicular to the grain, by strength grading of three wood species, are presented in this paper.

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The ratio of working stress to allowable stress on beams replaced with glued laminated timber graded to E55-F200 was investigated in three wooden houses which were build in an area of average snowfall. Due to a decrease of Young's Modulus of the replaced beams, it was found that existing flexure on some beams exceeded the flexure limit. However, there were no beams exceeding the allowable stress for bending strength and shear strength. For some beams exceeding the flexure limit, it was also suggested that sufficient safety margin for the flexure limit can be gained by increasing the beam height by 30 mm or 60 mm.

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In the present study, bending properties (modulus of rupture (MOR), modulus of elasticity (MOE), bending work (W), and Janka plastic modulus (Z)) were investigated for 10-ply laminated lumber composed of several softwood species. Sugi (Cryptomeria japonica D.Don) laminae were used for the inner 8 layers, and hinoki (Chamaecyparis obtusa Sieb. et Zucc.) or karamatu (Larix Kaempferi Carriere) laminae were used for the outermost 2 layers. In addition, laminated lumber members composed of 10 sugi laminae were also produced. In order to obtain the same MOE in all laminated lumber members, laminae were graded and then arranged for manufacturing the laminated lumber. Although the MOE showed almost the same value in all laminated lumber members, significant differences in MOR, W, and Z were recognized among the types of laminated lumber. In all types of laminated lumber, W and Z were mainly effected by deflection at the plastic region. In addition, W and Z were effected by the bending property of species forming the inner layers as well as that of the species forming the outermost layers.

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In the present study, shearing strength performance was investigated for three types of laminated lumber (10 ply) composed of several softwood species which have almost the same modulus of elasticity in static bending (MOE). Sugi (Cryptomeria japonica D.Don) laminae were used for the inner 8 layers and hinoki (Chamaecyparis obtusa Sieb. et Zucc.) or karamatu (Larix kaempferi Carriere) laminae were used for the outermost 2 layers. In addition, laminated lumber members composed of 10 ply sugi laminae were also produced. Almost no difference in shearing strength was observed among the three types of laminated lumber, suggesting that the shearing strength of laminated lumber might be related to the shearing properties of the laminae. There was no significant correlation between shearing strength and dynamic modulus of elasticity (E_fr) or MOE. Thus, it can be said that E_fr and MOE of laminae are not related to the shearing strength of laminated lumber. Shearing strength of laminated lumber was more affected by density than by E_fr. Based on the obtained results, MOE and density of laminae should be considered for manufacturing laminated lumber composed of several softwood species.

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In the present study, bending properties (modulus of rupture (MOR), modulus of elasticity (MOE), bending work (W), and Janka plastic modulus (Z)) were investigated for 4-ply and 3-ply laminated lumber composed of softwoods with different thicknesses of the elements. In 4-ply laminated lumber, sugi (Cryptomeria japonica D.Don) elements were used for the inner 2 layers, and hinoki (Chamaecyparis obtusa Sieb. et Zucc.) or karamatsu (Larix kaempferi Carriere) laminas were used for the outermost 2 layers. In 3-ply laminated lumber, a sugi element was used for the inner 1 layer, and hinoki or karamatsu laminas were used for the outermost 2 layers. Elements and laminas were graded by dynamic modulus of elasticity and then laminated for manufacturing the laminated lumber with the same MOE. Although the MOE was almost the same value in all laminated lumber members, significant differences in MOR, W, and Z were recognized among the types of laminated lumber. In addition, W was affected by the bending property (W) of species laminated at the outermost layers. On the other hand, Z was affected by the bending property (Z) of species laminated at the inner layers. In all types of laminated lumber, W and Z were mainly affected by deflection at the plastic region. When laminas and elements without finger joints were used, bending properties of 4-ply and 3-ply laminated lumber were almost the same as those of 10-ply laminated lumber.

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