The effect of thinning treatments on wood quality in an artificial plantation of Japanese larch (Larix kaempferi) was determined by measuring the annual ring width, ring density by soft X-ray densitometry, and dynamic Young's modulus of logs. Ninety-eight 40-41-year-old sample trees from 5 examination plots of different thinning rates (at 0%-50% thinning from full stocking) were examined. Four to 5 years after the experimental setup, the effect of thinning treatment was observed by analysis of variance and multiple comparison test in the each annual ring width at 4m and 8m in height. Thinning treatment had influenced each annual ring width until final cutting. The difference in ring width affected earlywood and latewood widths and latewood density. In a heavy thinning plot, although the width of annual rings was large, there was no reduction in annual ring density because the values of latewood width and latewood density were large. Dynamic Young's modulus of the logs was least in the un-thinned plot, and dynamic Young's modulus of the logs was highest in the 40% intensity heavy thinning plot compared to the 30% intensity standard thinning plot. Dynamic Young's modulus in the 50% intensity thinning plot was equivalent to that of the standard thinning plot.

View full abstract

The final objectives of this study are a proposed standard test method for shear failure used with the bending test method, and the estimation of pure shear strength of Japanese cedar (Cryptomeria japonica D.Don) that can be used for full-size timber members in the civil engineering field. In this report, a specimen from which pure shear strength can be obtained was designed by finite element method (FEM), and the shear failure tests using asymmetric four-point-bending tests were conducted as an elemental study. The specimens were Japanese cedar laminates composed of Japanese cedar glulam with Dahurian larch (Larix gmelinii (Rupr.) Kuzen.) as upper and lower laminae. To prevent embedment secondary parts were pasted at support and loading positions. Since in the test shear failure occurred prior to bending failure in all specimens at the neutral axis in the central length, it indicated that pure shear strength was obtained. The shear strengths and shear modulus of Japanese cedar glulam were calculated by comparing the values obtained from rosette gauges and the values obtained from FEM analyses. Shear modulus was 1/15 of Young's modulus and shear strengths were from 4.4 to 5.7MPa.

View full abstract

The objective of this study was to investigate the effect of the internal structure of wood-based materials on water migration in the through-thickness direction using X-rays. Oven-dry density profiles, water concentration profiles and moisture content profiles in the through-thickness direction of plywood and sheathing insulation fiberboard blocks in adsorption phase were nondestructively measured using the X-ray method used in the first report. It took more time for plywood to reach equilibrium than for solid wood. This was thought to be caused by (1) decreased air permeability due to adhesive layers preventing water vapor to migrate (2) decreased area of contact between cell wall substance and water vapor in lumens due to adhesive penetration into the cell wall surface. It took less time for sheathing boards to reach equilibrium than for solid wood. This was thought to be caused by high air permeability due to the porous structure.

View full abstract

Much driftwood appears at the coast after natural disasters such as heavy rain and typhoons. These driftwoods are gathered and disposed as wastes because they are nuisances for fisheries and very obstructive to the passage of ships. They are considered to be natural bioresources and have a potential for utilization as wood products. To utilize them, however, the influence of chlorine in wood should be examined. In this study, the effect of wood impregnated with seawater and distilled water on metals was evaluated by elementary analysis using the SEM-EDXA method. The metals used in this experiment were steel plate and aluminum plate. These plates were connected to woods with nails and screws. These samples were exposed under two different humidity conditions for up to 81 days. The results showed that the corrosion of metals was higher when in contact with seawater than when in contact with distilled water. Comparing metals, steel plates were the most susceptible and aluminum plates were scarcely eroded.

View full abstract

Floor-impact sounds generated in wood buildings might become noise which includes various frequency components. In such cases, it is insufficient to evaluate the noisiness of floor-impact sounds only by assuming loudness to be an index. The aim of this study is to find a new index that can evaluate the noisiness of floor-impact sounds in wood buildings. A wooden model floor consisting of flooring, shock absorbing materials, sound insulating materials and thick plywood fastened on a wood frame structure was constructed. Using recorded floor-impact sounds from the wooden model floor, not only subjective evaluations of loudness, sharpness and noisiness, but also psychoacoustical evaluations of loudness and sharpness were conducted. Consequently, it was clarified that the subjective loudness, subjective sharpness and noisiness of floor-impact sounds showed a high correlation with each other, and moreover the noisiness was modeled by the linear combination of nonstationary loudness and sharpness of psychoacoustical indices.

View full abstract