Current research issues of timber construction are discussed. Initial resistance design, durability design and post life design are considered, in a broad sense, as the components of structural design of timber construction. The following main issues are discussed here for each component.
1. Initial resistance design
1)Appropriate structural modeling ; 2)Relative resistance of structural members and joints ; 3)Practical simplification of stiffness calculation for semi-rigid structures ; 4)Reasonable synthesis of horizontal resistance of structural components ; 5)Site-work performance factor ; 6)Target resistance based on use and risk ; 7)Dynamic behavior of structural components and whole structures ; 8)Clear distinction between allowable resistance design and ultimate resistance design.
2. Durability design
1)Control of wood decay ; 2)Structural plan considering risk of decay ; 3)Initial design considering maintenance ; 4)Estimation of residual resistance.
3. Post life design
1)Reinforcement design considering degradation of members ; 2)Initial design considering reuse/recycling.

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Wood properties and their variation in the stem of 19-year-old Choerospondias axillaris trees, which grew fast and had straight stem forms, were investigated to clarify the potential of this species as a fast-growing tree in Japan. The diameter at breast height ranged from 31.9 to 39.5 cm. The air-dry density ranged from 0.53 to 0.57 g/cm³. The faster the diameter growth of a tree, the higher was the density. The patterns of distribution of air-dry density, microfibril angle (MFA), modulus of elasticity (MOE) and modulus of rupture (MOR) showed that there were low and high value zones in the stem. The facts that Choerospondias axillaris has straight stem form and the wood properties don't degrade in the upper position make it possible to use stems up to 10 m in height.

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Lignophenols were prepared through a phase-separation system composed of p-cresol and sulfuric acid. Composites of wood meals and lignophenols (Wood-Lignophenol composites) were molded by hot-pressing and their physical properties were examined.
The modulus of rupture (MOR) and the modulus of elasticity (MOE) in bending of wood-lignophenol composites were roughly improved along with rising molding pressure and increasing lignophenol content. However, the strength for high lignophenol content (15 wt%, 20 wt%) decreased when the molding pressure was 20 MPa. These results are caused by the gas generated by thermal structural conversion of the lignophenol. On the other hand, water absorption and thickness swelling decreased with increasing lignophenol content. Water absorption and thickness swelling were greatly influenced by molding pressure and the physical properties of the lignophenol, respectively.
Bending strength and water-resistance were improved by adding a small amount of NaCl and CaCl₂·2H₂O, and the effect of CaCl₂·2H₂O addition was remarkable.

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House interior materials are not directly exposed to rain and only receive the sunlight that penetrates through window glass. Therefore, to develop a method of evaluating the photo-stability properties of interior materials, we applied the newly designed accelerated photo-stability test to wood and wood-finish materials separately under exposure to transmitted metal halide lamp light through window-sash glass and transmitted xenon lamp light through glass filter. The results are as follows :
When the light-colored softwood samples were exposed to the transmitted metal halide lamp light, L^* values decreased, whereas a^* and b^* values increased. The degree of color changes decreased in the order of single glass, double glass, low emissivity double glass, solar reflection double glass, and laminated solar reflection double glass. Especially when exposed to the light through laminated solar reflection double glass and solar reflection double glass, a^* and b^* values decreased once at the first stage, and then increased gradually, and the color difference also increased, decreased and finally increased from the beginning to the final stage. Moreover, we have confirmed the influence of the different types of window glass on the photo-stability of the various wood-based house interior materials. These results have proven that the test methods using the transmitted metal halide lamp light are effective in the evaluation of the photo-stability properties of house interior materials which are exposed to transmitted light through window glasses.

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The purpose of this study was to obtain the basic data required to design a raised bed for plants suitable for the horticultural therapy in which able-bodied or frail elderly persons can perform gardening in a relaxed standing posture. Comfortable heights of working surface and reach distances were measured in a bimanual transplant task. The results obtained were as follows : (1) Among able-bodied elders, comfortable heights selected by most males were 85 and 90 cm, while those of females were 75 and 80 cm. The height of the raised bed suitable for standing work could be roughly estimated as 20 cm below elbow height. Comfortable reach distance ranged from 20 to 40 cm both in males and females. (2) In frail elders, 70 cm was selected as the comfortable height. However, it was found by interviews that sensuously there was no great difference between 70 cm and 80 cm. The range of the comfortable reach distance was from 10 cm to 45 cm. (3) Taking together, the range from 10 cm to 40 cm could be a desirable reach distance for both kinds of elders. (4) Many elders complained of possible backaches after the transplant task using lower raised beds. In addition, elders with disabilities also complained of light fatigue around their knees.

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Species-specific random amplified polymorphic DNA (RAPD) markers of Quercus serrata Thunb. (konara), Quercus crispula Blume (mizunara) and Quercus alba Linn. (white oak) were investigated to identify the species of Section Prinus in the subgenus Quercus by using molecular genetic information. Polymerase Chain Reaction was performed with a set of 10 mer or 12 mer primers and total DNA as template. A total of 144 (72 sets) primers were used in the RAPD analysis. We found that six RAPD markers were species-specific : one distinguishes konara from mizunara and white oak ; four distinguish mizunara from konara and white oak ; and one distinguishes white oak from konara and mizunara. All of the six RAPD markers were highly reproducible and resulted from distinct amplicons.

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