An orthogonal cutting experiment of air-dried hinoki (Chamaecyparis obtusa) was conducted and the fuzzy grain recognized as a whitish cluster on the finished surface was extracted by digital image data processing. The relative area of fuzzy grain took the maximum values of 6 to 10% for the contact angle of annual rings (ϕ) of 0°, decreased as the contact angle increased, then took the minimum values of 3 to 4% for the angle of 45°and finally increased in accordance with the contact angle. It was revealed from SEM observation that the cluster of fuzzy grain consists of cells around the ray that were scraped off in the cutting, but not separated as complete chips, were crashed by the travelling cutting edge, and were finally raised up from the wood surface after the cutting. The conformation of the cluster changed characteristically in accordance with the contact angle of annual rings. It was also revealed that the number of AE (Acoustic Emission) events detected in the cutting process correlated positively with the relative area of fuzzy grain.

In order to provide the mechanical properties and seismic performance of CLT shear walls to which tensile bolted joints and screwed steel joints were applied for vertical restraint, cyclic lateral loading tests and pseudo-dynamic tests were conducted on 3-ply sugi CLT shear walls. Moreover, the analytical model was validated by comparing the time-history earthquake response analysis and pseudo-dynamic test results for these types of shear walls. The relation between the magnitude of input ground motion and the horizontal displacement response was investigated by conducting time-history earthquake response analysis on several earthquake records and artificial waves with variable magnitude of input ground motion. Also, the possibility of replacing the tensile bolted joints by screwed steel joints was discussed. The yield strength and the maximum strength of shear walls with screwed joints were 20% higher than those with tensile bolts in the cyclic lateral loading tests. With the same seismic wave input in the pseudo-dynamic tests, the maximum response displacements of screwed joint specimens were smaller than those of tensile bolt specimens. Furthermore, the response displacement of earthquake response analysis showed good agreement with pseudo-dynamic test results. It is suggested that CLT shear walls with screwed steel joints give enough performance compared to shear walls with tensile bolt joints.

Medium density fiberboard (MDF) was subjected to outdoor exposure for 21 years to evaluate its durability, and reduction in the modulus of rupture (MOR) was then inferred using Bayesian analysis. The durability of MDF after outdoor exposure of 21 years was evident. Different posterior predictive distributions of MOR were apparent for each exposure time due to irregular variation of variances in MOR. As a result, it was not possible to adequately infer the posterior predictive distributions of MOR using Bayesian analysis with a model that included constant MOR variance. The irregular variation of variances in MOR was therefore considered to be due to random effects, and a hierarchical model that included these random effects was constructed: the posterior predictive distributions of MOR were then adequately inferred using Bayesian analysis with the hierarchical model that included the random effects. In addition, 95% prediction intervals were inferred using the model including constant variance in MOR or the hierarchical model including the random effects; however, the 95% prediction interval of the latter model was found to be more suitable than that of the former model.

Strength properties (modulus of rupture, internal bond strength, lateral nail resistance, and nail-head pull-through) of particleboard were measured, and were subjected to conventionally statistical and Bayesian analyses. All strength properties could be fitted to normal distributions. In conventionally statistical analysis, mean and variance are constant values that have one true value. Therefore, when mean and variance are distributed, probability distributions of strength properties could not be inferred suitably using conventionally statistical analysis. In Bayesian analysis, because mean and variance are considered to be distributed, their distributions could be used to infer probability distributions of strength properties. The mean and variance of products with large variance of strength properties, such as particleboards, are considered to be distributed. Thus, Bayesian analysis is useful in the quality control of particleboards.

In 2014, large numbers of specimens of buried wood were excavated at the construction site for Nihonkai-tohoku expressway in Nikaho, Akita prefecture, Japan. They had been buried by the Kisakata debris avalanche following a sector collapse at Mt. Chokai in 466 B.C. The aim of this study is to identify the species of the buried wood and to record its characteristics, including colors. Sections made by sliding microtome were observed under a light microscope and samples were identified on the basis of anatomical features. As a result, wood identification of 39 buried specimens, included: Castanea crenata, Quercus section Quercus, Zelkova serrata, Aesculus turbinate, Fagus, Ostrya japonica, and Cryptomeria japonica. The color of buried wood was different from that of wood from living specimens of the same species. Buried wood of C. crenata and Quercus species was black in color, of Z. serrata was dark green, of A. turbinate, Fagus, and O. japonica was brown, and of C. japonica ranged from green-gray to brown. These buried wood specimens are valuable, not only as a model sample to analyze the mechanism by which color and strength of wood change during prolonged burial, but also as a part of the cultural heritage of the area. Therefore, it is significant to know the characteristic properties and chemical composition of buried wood specimens. Our results should provide fundamental and practical information for future investigation.

The Japanese tea room is thought to have been created by fusing elements of Japanese culture, Zen, the way of Yin Yang, and other original ideas, and is believed to embody Japanese culture most symbolically. In this research, materials used in a modern Japanese tea room, Basyo-ou Kokyo-zuka “Hyochikuan” located in Mie Prefecture, were studied. This tea room was designed by Kaichiro Usui (1898-1969), one of the important modern tea room designers in the tea ceremony school Omotesenke. Remarkably, an old document written by Kaichiro Usui that estimated wood materials planned to be used for this tea room has remained. The aim of this study is to identify the wood species in this tea room and to compare the results with the descriptions in the old document. Our identification revealed that, while the same wood species written in the old document were used for most items, some important ones were made by completely different species. Though the studied materials are limited, our results provide basic information about the architectural works and wood selection of Kaichiro Usui.