The off-axis Young’s modulus of plywood was obtained by conducting longitudinal vibration tests using specimens with various widths and performing a subsequent numerical analysis on the test data. The off-axis Young’s modulus was dependent on the width of specimen particularly when the off-axis angle ranged from 30° to 60°, and it approached the value theoretically predicted by the transformation rule as the width of specimen increased. Therefore, the width of specimen should be sufficient to measure the off-axis Young’s modulus of plywood accurately using the longitudinal vibration test.
Compressed wood is used as building interior material such as the floor material after fixed permanently by such as steam treatment. However, the compressed wood is swollen by absorbing water without recovering large amount of compressed deformation, despite it was fixed permanently. The dimensional stability of compressed wood for moisture is very important for safe use of building material. Therefore, swelling behavior of cell was observed in compressed wood and the relationship between cell shape and swelling behavior of cell was discussed. The swelling in radial direction of wood compressed 50％ was four times larger than that of uncompressed wood. In the visual fields of a microscope, four different deformation types of cell lumens were observed. The increase in area of cell lumens is different among the four types. The increase in area of cell lumens is much different between S-shape cells and elongated shape of cells. In particular, the cells deformed to S-shape are hard to be increased the area of cell lumens by swelling. This result suggests that deformation types of cell lumens affect the swelling behaviors of compressed cells. From the above results, it might be possible to improve the dimensional instability of the compressed wood by giving deformations as increasing the S-shape cells.
For the development of manufacturing technology of boxed-heart Sugi timber with appropriate preservative treatment, we have been examining the effects of the drying method before impregnation on the quality of the products with preservative treatment. We used boxed-heart Sugi timber from Nara and Oita which were treated either by medium-temperature drying, by a combination of medium-temperature drying and radio-frequency heating, by a high-temperature setting drying, or by a combination of high-temperature setting drying and radio-frequency heating. We investigated the penetration of the timber preservatives as well as the dimensional change before and after the impregnation. As a result, we confirmed that there were parts with insufficient penetration in boxed-heart Sugi timber from the above prefectures which were dried by a high-temperature setting treatment. Moreover, there were some cases in which such timbers had lower solution uptake and penetration ratio of preservatives than those that were dried with medium-temperature. Also, back split was necessary in order to prevent surface checks during drying process after impregnation and curing process. Lastly, using radio-frequency heating in addition to medium-temperature for drying before impregnation showed a possibility of producing materials without poor penetration, reduced solution uptake or penetration ratio in short time.
The aim of this study was to evaluate the structural performance of nail joints subjected to different moisture contents (MC). In this study, the nail withdrawal and the single shear tests were conducted. The nails were inserted into sugi and larch specimens in the parallel or perpendicular to the grain directions before MC control. As a result, the nail withdrawal resistance increased with decreasing MC when MC was lower than 30%, and did not exhibit the similar trend when MC was higher than 30%. The nail withdrawal energy per unit length of sugi specimens decreased with increasing MC when MC was lower than 30%, and did not show such a trend when MC was higher than 30%. However, larch specimens did not show the tendency as sugi ones. The yield strength of single shear tests slightly increased as MC decreased in the parallel to the grain direction, but did not show the similar trend in the perpendicular to the grain direction. The correlation between initial stiffness and MC was found to be poor in both parallel and perpendicular to the grain directions.
This study focused on solute diffusing into cell walls in solution-impregnated wood under conditioning, process of moderate drying of solvent. The purpose of this paper was clarification of the effect of evaporation rate of solvent on the solute diffusion in the impregnated wood. Wood samples impregnated with an aqueous solution of polyethylene glycol (PEG) were conditioned in an atmosphere with constant temperature, with equilibrium relative humidity (RH) of 32 or 75%, and with three types of convection. For both the RHs, the forced convection caused the highest evaporation rate of water, which was indicated by the mass of the sample, followed by the natural convection without and with mesh barriers. The total amount of PEG diffusing into cell walls, which was evaluated using the dimension of the sample dried in a vacuum after the conditioning, decreased and increased at RHs of 32 and 75%, respectively, with the increase in the evaporation rate. This amount at 75% was equal to or larger than that of 32%. For the efficient conditioning, it is preferable to condition the impregnated wood sample to the equilibrium moisture amount at which the ability of aqueous-PEG solution in the sample to swell wood is the highest, as soon as possible, and subsequently to dry it with slower evaporation rate.
Cell deformation behavior of Japanese cedar (Cryptomeria japonica) and Japanese cypress (Chamaecyparis obtuse) were observed during progress in the radial compression using a scanning electron microscope (SEM). The deformation behavior were defferent between Japanese ceder and Japanese cypress. In Japanese ceder, the early wood cells close to the boundary of the annual ring did not buckle up to 55% of compressing ratio of the annual ring (CR), whereas those of Japanese cypress buckled at 32% of CR. This means the earlywood cells close to the boundary of annual ring of Japanese cypress buckled easier than those of Japanese cedar. The dimensional ratios in radial/tangential dimension (R/T) of uncompressed cells were measured from SEM images, and then were compared with the deformation pattern in each species. A significant correlation were found between CR when the cells buckled at the respective radial position in an annual ring and R/T of the cell at each position. From this, it can be concluded that the compressive deformation behavior of cells was related to the distribution of R/T of the cells in an annual ring.
We used tunicate cellulose and cotton cellulose as starting materials, and performed acetylation to them with heterogeneous and homogeneous reaction. The obtained cellulose acetates were dissolved in N,N-dimethylacetamide, and their viscosities and dynamic viscoelastic properties were measured. Cast films were prepared from the dichloromethane solution of the cellulose acetates. Their infrared spectra and visible absorption spectra were collected; and moreover, their contact angle measurements and tensile strength measurements were performed. From these results, we discussed how the characteristics (especially, molecular weight) of the starting celluloses affected the obtained cellulose acetates. The cellulose acetate film prepared with the homogeneous reaction showed higher hydrophobicity and intensity than that prepared with the heterogeneous reaction. In addition, the cellulose acetate film prepared from tunicate cellulose showed higher hydrophobicity and intensity than that prepared from cotton cellulose. It suggests that the hydrophobicity and intensity depend on the molecular weight of cellulose. On the other hand, although the cellulose acetate prepared from tunicate cellulose with the heterogeneous reaction had lower molecular weight, the hydrophobicity and the intensity of its film were larger than the film prepared from cotton origin with the homogeneous reaction having higher molecular weight. It shows the possibility that there is uniqueness that cannot be explained only by a molecular weight of cellulose.
In this paper, the parameters (e.g. coefficients of restitution, friction coefficient, translational and rotational energies, and their energy ratio) for spherical boulder impacting on rock plate will be presented based on our experimental and numerical analysis data by free-fall-rebounding laboratory experiment using high-speed video camera system. This paper explains influence of combination of normal and tangential components of coefficients of restitution for numerical analysis on rockfall motion. In this study, friction coefficients of slider for numerical analysis are decided based on tilt test, and coefficients of restitution by experimental data. The result of numerical analysis showed that the increasing trend of the tangential component of coefficients of restitution can be modeled with spring-dashpot-slider system. Furthermore, this study investigates the rotational motion by numerical analysis of rigid model. In this numerical analysis results, the input of friction coefficient is one of the factors that greatly affect the value of tangential component of coefficients of restitution and rotational energy.
Ground subsidence due to groundwater extraction is a severe problem of many cities in depositional plains all around the world. In the Kanto plain, where the capital region of Japan is situated, ground subsidence with a few centimeter per year has occurred in recent years especially in the northern part of the Kanto plain. However, the detailed spatial distribution of subsidence has not been revealed yet. In this study, we estimated the spatial distribution of ground subsidence of the northern Kanto plain from August 2006 to February 2011 by persistent scatterer SAR interferometry. Persistent scatterer SAR interferometry is a satellite-based remote sensing method to map surface displacement, and has an advantage for mapping displacement in a broad area with a fine spatial resolution. The estimated ground subsidence was comparable with GPS and leveling data. Moreover, the spatial pattern of ground subsidence was likely correlated with geological structure of the area. Our results demonstrate the effectiveness of persistent scatterer SAR interferometry for monitoring ground subsidence.
Disaster emergency evacuation plan is important especially for the cities where nuclear power stations are located. Once a mega disaster occurs, smooth evacuation is necessary for the people living near the nuclear power stations. This study conducted multi-agent simulations for disaster evacuation in Tsuruga city, where several nuclear power stations are located near the city. The results showed that the evacuation using buses was effective to reduce the total evacuation time, if a sufficient number of buses are prepared in a short time. Two-step evacuation was effective to reduce the total evacuation time, however, this method was inefficient at the beginning of evacuation. The combined method using buses and two-step evacuation was the most effective to reduce the total time and could solve the both problems.
Many post-construction anchors can be used in construction and civil engineering field. Bonded and mechanical anchors are representatives of such anchors. The bonded anchor is embedded in base concrete with an adhesive such as the epoxy adhesive. However, the deviation of the compounding ratio of the adhesive is one of the major problems affecting the functioning of bonded anchors. To solve some of these problems, we developed a bonded anchor with the acrylic adhesive in the bridge structure. Properties of the acrylic adhesive for both of developed bonded anchors are described in the present.