Recently, wood and wood products are often used for large-scale structures, and this subject suggests that hidden defects such as crazes, crushes, and cracks tend to be contained in the wood and wood products. Therefore, it is important to obtain proper knowledge of the failure behaviors of these materials to prevent catastrophic failure of the structures, and fracture mechanics is most effective in analyzing these failure behaviors. This paper describes current progress in research on the failure behaviors of wood and wood products based on fracture mechanics, as well as concerns which are not yet sufficiently solved.

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To determine the effect of initial spacing on growth and wood properties of sugi (Cryptomeria japonica D. Don) cutting cultivars, six cultivars (Iwao, Hinode, Yamaguchi, Yaichi, Shakain, Yabukuguri) were examined. They were identified based on MuPS (Multiplex PCR of SCAR) markers type and had been planted at 1500, 3000, 5000 trees/ha.
Effects of initial spacing on growth and wood properties studied were significantly less than differences between cultivars. Diameter and volume growth for dense initial spacing was less than that for wide initial spacing. Wood density of mature wood, L^* of heartwood, dynamic Young's modulus of logs, compressive strength and modulus of elasticity for dense initial spacing were slightly higher, but green moisture content of heartwood and sapwood, and a^* of heartwood were lower than for wide initial spacing. Initial spacing had an effect on mechanical properties which was different for Yabukuguri than for the other 5 cultivars. Thus, wood properties of sugi were slightly influencd by initial spacing, although it was mainly influened by inheritance factors such as cultivar.

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In the previous papers, it became clear that the effect of delignifying on mechano-sorptive (MS) creep of radial specimens was quantitatively remarkable, but was qualitatively slight. In this paper, we investigated the effects of delignifying treatments on MS creep of the longitudinal specimens and the obtained results were compared with the case of radial specimens.
The obtained results were summarized as follows :
1. During repeating Ad (loading only during adsorption) or Da (loading only during desorption) processes, total compliance (J_T) and set increased. Delignifying increased the amounts of J_T and set, while the differences in J_T and set between Ad and Da processes were small.
2. Delignifying increased J_T for AD (continuous loading) process : J_T of strongly delignified specimens was 1.7 times as greater than J_T of controls after five moisture cycles. While the deflections increased during each desorption, the deflections decreased remarkably during each adsorption except for the first one.
3. The effects of delignifying were more pronounced for radial specimens, where J_T of strongly delignified specimens was 5.4 times greater than J_T of controls (1.7 times greater for longitudinal specimen). The internal force presumably acts directly on the matrix of cell wall of radial specimens, while the combination of microfibril and matrix might reduce MS creep for longitudinal specimens.

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Carbonyl compound concentration was surveyed in the indoor air of fifty-two new wooden residential houses constructed with different construction methods from 2001 to 2002. House construction method did not affect the carbonyl concentration of the indoor air. Actual air concentration of formaldehyde was 0.118 ppm on average. However, the concentration converted to 28°C/50%RH was almost the same as the guideline value (0.08 ppm). About half of the surveyed houses had formaldehyde concentrations more than the guideline value. Average actual air concentration of acetaldehyde was 0.171 ppm, nearly six times greater than the guideline value (0.03 ppm). Increasing the amount of wood-based material used, the acetaldehyde air concentration decreased, but the formaldehyde air concentration did not.

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Adsorption of CO₂ gas onto charcoals was studied at the ice-water temperature (273 K) in order to establish a method for a reliable determination of pore size distributions in charcoals from wood and bamboo. The pore size distributions were determined by analyzing adsorption isotherms using the HK method (Horvath-Kawazoe method). The pore size distributions obtained were highly reproducible and reliable, and peaks of pore size distributions in the charcoals were found at about 0.5 nm. Based on size, these micropores in charcoals were judged to result from a disordered-graphite-like structure. It was previously found that wood and bamboo charcoals have only a small amount of mesopores and no peak of the distribution in the mesopore region. From the previous and the present results, it can be concluded that the micropores mentioned above are responsible for a steep increase found in the adsorption isotherms of water vapor in a range of about 40 to 60% relative humidity.
Pore size distributions were also determined for the charcoals from wood pretreated with polyethylene glycol (PEG), as an attempt to obtain some information about the possibility of controlling micropore structure in wood and bamboo charcoals. A small increase in larger pores above 0.5 nm was found in the pretreated charcoals as compared to the untreated charcoals.

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Five popular adhesives of urea resin (UF), melamine-urea cocondensed resin (MUF), phenol resin (PF), phenol-resorcinol resin (PRF), and aqueous polymer isocyanate (API) for wood based materials were analyzed by the inventory analysis. It was calculated that energy consumption and emissions of CO₂, NOx and SOx for production of 1 kg resin using unit processes from oil drilling for material's production to resin production. It became clear that MUF and PRF consumed the largest amount of energy and exhausted maximum amount of SOx among five adhesives. On the other hand, UF consumed the least energy and exhausted minimum SOx which are equivalent to the range of 57 and 67 percents of those of MUF and PRF, respectively. PF and API were recognized to be medium ones among five adhesives analyzed. CO₂ and NOx emissions of API were remarkably large in such a condition that these amounts were more than six times as long as other resins.
It was highly recommended that environmental loads of an adhesive should be judged by not the weight unit but the functional unit in case of life cycle assessment of wood based materials.

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To investigate the effects of crossbanded laminate ratios in laminated veneer lumber (LVL) on its bearing properties, tension-type bearing strength tests of drift-pin joints were made. The LVLs of parallel laminates and two types crossbanded laminates were made of rotary-cut veneers of sugi(Cryptomeria japonica D. Don). Deformation rates (embedding speed of the drift-pin) of the tests were 5, 50 and 500 mm/min. The test results were approximated by a perfect elasto-plastic relationship. Conclusions were as follows :
1)The parallel laminates LVL showed brittle fracture with a small embedment of the drift-pin. However the LVL with crossbanded laminates showed very ductile behaviors, since the drift-pin could be embedded into them continuously. From observations of crossband veneer fracture in the LVL, it became clear that the wood fibers of the crossband veneer resisted the embedment of the drift-pin.
2)Initial stiffness decreased with increasing crossband veneer ratio in the LVLs. The stiffness of LVL with a 40% crossband veneer ratio became from 50% to 60% of that of the parallel laminates LVL. However, the ultimate bearing stress tended to increase with increasing crossband veneer ratio of the LVL on condition that the deformation rate of the tests was fast.
3)The ductility ratio (yield embedment deformation to ultimate embedment deformation) became from 16 to 23 for the LVL with crossbanded laminates, while for the parallel laminates LVL it was less than 2. The bearing energy of the LVL with crossbanded laminates became from 24 times to 35 times greater than that of the parallel laminates LVL.

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