As the first study of maximum possible tensile deformation of wood, lateral tensile deformation properties of hinoki (Chamaecyparis obtusa) were investigated, and the important factors to increase the tensile deformation of wood were examined in this report. Tensile deformation properties were measured in dry air and in water at both 25°C and 80°C. The test samples had different angles of the tensile direction to the annual rings (0°, 45°, 90°). The results obtained were as follows: 1) For samples with different angles, tensile elastic modulus, strength and failure strain were clearly shown at 25°C and 80°C in the dry and the water saturated condition. 2) In all of the measurement conditions, samples of angle 45° had larger values of tensile failure strain than the samples of angles 90° and 0°. This was caused by the shearing deformation of cells which showed diamond-shaped deformation during increasing tensile stress. 3) In the dry condition the tensile failure strains were not very different at 25°C or 80°C in all of the samples. However, in the water saturated condition the tensile failure strains were much larger at 80°C than at 25°C. Due to the multiplier effect of temperature and moisture, the molecular motion of the cell walls becomes active and decreases resistance to external stress. This change in physical property increases the lateral tensile deformation of wood. These results suggest that in order to increase lateral wood tensile deformation, activation of the molecular motion of the cell wall and capability for deformation of cell shapes are important factors.

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In Akita prefecture, all wood type wooden check dams which are composed of wood members and lag screws have been studied and developed. The cost of the lag screws amounts to 20% to 30% of the entire construction cost. Therefore, as a substitute for the lag screws, we examined deformed steel bars which cost a tenth of the lag screws and would be very economical. Since pull-out force and shearing force can occur at joints of the wooden check dam simultaneously under design load conditions, the same performance would be required for the deformed steel bars as for the lag screws. In this study, we conducted pull-out and shear tests of the joints for different embedment depths of the deformed steel bar. Shear test results were compared with the yield capacity according to European yield theory. The results can be summarized as follows: In regard to shearing strength, the deformed steel bars give a performance equivalent to that of lag screws. In regard to pull-out strength, the deformed steel bar is a possible substitute for the lag screw. However, pull-out performance of the deformed steel bar is only about 80% of that of the lag screw. In order to expect the same pull-out performance as for lag screws, the pre-drilled hole diameter needs to be 14mm and the embedment depth needs to be 200 mm.

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Pyroligneous liquids from woody materials are a valuable forest resource, although they are a by-product of charcoal production. Chemical deodorant effects of pyroligneous liquids were investigated to expand their applications. Three pyroligneous liquids, which were made from nara (Quercus serrata Thunb. and/or Quercus crispula Blume), ubamegashi (Quercus phillyraeoides A. Gray) and mosochiku (Phyllostachys pubescens Mazel), were evaluated through deodorization tests. Five chemical compounds, ammonia, trimethylamine, hydrogen sulfide, methyl mercaptan and acetaldehyde, were adopted as sources of offensive odors. All the pyroligneous liquids showed remarkable deodorant effects on ammonia and trimethylamine, which are basic compounds. Pyroligneous liquids from nara and mosochiku had no or few deodorant effects on hydrogen sulfide and methyl mercaptan, while both the sulfur compounds showed a reduction of about 30% through a 24-hour deodorization test using pyroligneous liquid from ubamegashi. It has been clarified that considerable amounts of acetaldehyde were volatilized from all the pyroligneous liquids.

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Four phosphorus type chemicals were mixed with disodium octaborate tetrahydrate in various mixing ratios. These mixed chemicals were impregnated into Sugi wood, and the treated woods were evaluated for heat release performance by cone calorimeter tests. Total heat release of woods treated with mixed chemicals at ratios of 9:1 and 8:2 for diammonium hydrogenphosphate and poly-phosphatic carbamate, and treated with guanidine phosphate at mixing ratio at 9:1 was less than that of woods treated with mixtures using phosphorus type chemicals. However, woods treated with mixtures using ammonium dihydrogenphosphate did not result in the mixing ratios that decrease total heat release. According to the observations of combustion behavior during heating, it was concluded that decreases of total heat release for wood treated with mixed chemicals were related to suppression of glowing of wood. The woods treated with mixed chemicals at mixing ratios that decreased the total heat release as cited above, also showed decreased total mass loss or effective heat of combustion than the woods treated with phosphorus type chemicals used in the mixture. According to these data, it was concluded that mixed chemicals that decreased total heat release of wood, caused this by a synergistic effect between the phosphorus and the boric type chemicals.

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