In order to develope a rational joint system in traditionally joined timber frame structures, we designed a new drift-pin joint composed of a steel pipe drift-pin with a glass-fibre-reinforced nylon (GFRP) plate inserted into a slit of the timber. Lateral resistance tests of the joint with a single drift-pin were conducted to evaluate the effects of dorift-pin shape on maximum and yield loads. These properties were compared with a common drift-pin joint with a steel plate. The joint with a nylon plate had 60% of the stiffness, 90% of the maximum load and 90% of the yield load as compared to a steel plate. Both nylon and steel plate joints with steel pipe drift-pins had 80% of the lateral strength of common drift-pins. Maximum and yield loads of nylon plate joints with steel pipe drift-pins under reversed cyclic loads were equivalent to those under monotonic loads, and no failure of nylon plate had occured under reversed cyclic loads at the yield resistance level after 150 cycles.
Aged baulk timber in a historic building of Fukushoji-temple (national cultural property) was investigated to estimate the extent of deterioration of aged timbers. The samples were all Pinus densifora, but installed in different years, approximately 1500, 1662 and 1836. They were of similar rank order and built in similar circumstances. The timbers had insect damage by Nicobium hirtum. Soft X-ray transfer imaging and density measurements revealed that the insect damage was more severe with increasing age. To discuss change by aging of wood substance itself, insect-damaged parts were eliminated and undamaged parts were investigated : the oxidization temperature and Young's modulus in L-direction seemed to be higher for the present than the aged wood, but clear relation with aging was not detected. X-ray diffraction analysis of undamaged part revealed that relative cellulose crystallinity of aged samples was similar to or rather higher than that of the present sample. The crystallinity was negatively correlated with the Young's modulus. The holocellulose content of the undamaged parts seemed to decrease with aging. These facts imply that slight changes of chemical components other than crystalline cellulose might occur by aging. Comprehensively, in this case, the practical issue was insect damage, rather than deterioration by aging.
We examined the rooting of viviparous seeds of Kandelia candel planted at different depths, as a part of the basic studies aiming at mass production of seedlings for efficient afforestation of mangroves. Shoot elongation of the viviparous seeds was promoted by increasing the depth of planting, which is in agreement with previous reports on the rooting of deeply planted cuttings of Viburnum awabuki and Prunus persica. However, in the lower part of the viviparous seeds where the root primordia existed before planting, the depth of planting influenced neither the part nor the number of rootings. On the other hand, in the upper part of the viviparous seeds where the root primordia appeared after planting, the rooting part was expanded and the number of rootings increased by deep planting. These results suggest that the contact of the upper part of the viviparous seeds with the culture medium at the time of planting stimulated the formation of root primordia in the upper part. In addition, no rooting part was found at approximately 2 cm between the upper part and lower part.
The effects of temperature on mechano-sorptive (MS) creep of delignified hinoki wood (Chamaecyparis obtusa Endl.) were investigated using longitudinal (L) and radial (R) specimens during adsorption and desorption over the temperature range of 20°–80°C. The results were compared with those of stepwise delignified specimens tested at a constant temperature of 20°C. It was found that the effects of temperature on the MS creep of delignified specimens are more remarkable than for untreated specimens. The tendencies of increasing MS creep with temperature, delignification, and their combination were observed. The increase in MS creep for L specimens was relatively small and almost equal in both adsorption and desorption processes, while for R specimens the MS creep was small in desorption, but significantly different in adsorption. In addition, good correlation was observed between the MS coefficient (K) and instantaneous compliance (J0). The increase in MS creep occurs as a result of temperature increase or decrease in lignin content, or their interacting effects. However, in the case of desorption for R specimens, the increase of MS creep was unexpectedly small due to a remarkably increased J0.
In order to understand the fixation mechanism of compressive deformation of sugi (Cryptomeria japonica) by steaming or heating, we studied changes in chemical components and mechanical properties during steaming or heating at 180degreesC. When steamed for 60 minutes, alkali solubles in hollocellulose decreased remarkably, which corresponded to reduction of residual stress, strain recovery, yield stress and bending strength. From quantitative analysis of neutral sugar contained in the steamed samples, hemicellulose was estimated to leach markedly during steaming. This was interpreted as the result of release of internal stress and formation of bonds of hydrophobic nature, causing fixation of the compressed wood. On the other hand, heating for 720 minutes caused a remarkable decrease not only of hemicellulose but also of alpha-cellulose which coincided closely with lowering of the strain recovery. During heating, degradation of cellulose as well as a change of hemicellulose was thought to cause fixation of compressed wood.
The accumulation of data on the structure and function of cellulases and related enzymes from various organisms has led us in the last decade to change the concept on the fungal system of cellulose degradation in the latest decade. For example, fungal cellulases have been classified into 8 different families among the category of glycoside hydrolases. In addition, the importance of the redox enzyme cellobiose dehydrogenase in the fungal system of cellulose degradation has been demonstrated. During cellulose degradation by the basidiomycete Phanerochaete chrysosporium, only this enzyme can participate in the extracellular metabolism of cellobiose instead of beta-glucosidase. Moreover, quite recently, total genome sequence of P chrysosporium has been disclosed by the DoE Joint Genome Institute in USA. Using this information, cDNA cloning of various cellulase genes from P chrysosporium and successive production of recombinant proteins from them has been greatly facilitated.
In order to investigate the influence of alkali treatment on the Young's modulus and on hygroscopic properties, the Young's modulus in bending was measured after wood samples (Picea jezoensis Carr.) were treated with aqueous solutions of various NaOH concentrations and then conditioned at various relative humidity conditions.In the oven-dry condition, the density of treated wood samples increased with increasing NaOH concentration, while their Young's modulus increased in the NaOH concentration range of 0 to 10%, and decreased in the NaOH concentration range of 10 to 15 %. These observations were due to both increases in the density and decreases in the degree of crystallinity in the transformation from cellulose I to cellulose H. The dependence of Young's modulus on relative humidity varied with NaOH concentration. At higher NaOH concentrations, the ratio of Young's modulus at a given relative humidity to that in the oven-dry condition started to decrease at low relative humidity and decreased more markedly at high relative humidity.The dependence of Young's modulus on relative humidity indicated that the alkali treatment was associated with both transformation of cellulose and increases in the proportion of amorphous components.
Gypsum-bonded particleboards overlaid with non-woven glass fabric on top and bottom surfaces were manufactured. The effects of board density and basis weight of non-woven glass fabric on modulus of rupture (MOR) and internal bond strength of boards were examined. The results are as follows: 1) The MOR in both dry and wet conditions, modulus of elasticity (MOE), and thickness swelling of gypsum-bonded particleboards were improved by reinforcement with non-woven glass fabric. However, the internal bond strength was reduced. 2) The MOR, MOE and internal bond strength of boards increased with increasing weight ratio of gypsum dihydrate. 3) The paper overlay on gypsum boards improved the MOR of low-density boards, while the wood particles improved the MOR of high-density boards. 4) The bending properties and screw withdrawal resistance of the gypsum-bonded particleboards overlaid by non-woven glass fabric were improved, but the internal bond strength was reduced, when the basis weight of non-woven glass fabric was increased.
The cell wall is one of the most basic structural elements of wood. How to measure precisely the cell wall thickness ? The cell wall thickness of early wood tracheids in softwoods being only 1 - 2 mum, and sometimes less than 1.0 mum, it is difficult to measure it quantitatively by ordinary light microscopy. The edge problem between wall and cell lumen was shown to be the essential obstacle, to say nothing of the light microscope resolution. Moreover, preparation and microscopic conditions such as section thickness, contrast enhancement and focussing were shown to seriously affect the measured values. SEM, the confocal laser scanning microscope and other microscopes each have their peculiar weak points for quantitative analysis. If the definite boundary at the edge can be determined, the measurement becomes accurate. We improved the Au-lining method and the effects were inspected statistically by comparison with other methods. The results show that ordinary sliding microtome sectioning and staining result in serious over-estimation of thickness values. The Au-lining method resulted in measurements of wall thickness of high accuracy and reliability. The method is as follows: after softening the wood block in boiling water, transverse sections 100 mum thick were cut on the sliding microtome and the walls were stained with 0.1% safranine water. The sections were washed with ethanol to remove staining other than in the intercellular layer. The sections were sputter-coated with gold following ordinary SEM procedures. After embedding the sections in epoxy resin, thin sections 3 mum thick were sliced again and observed under the light microscope. The thickness of single and also double cell walls can be determined from the distance between the Au-lining layer and the intercellular layer.
The deformation behaviour of wood around moment-resisting joints was analysed using digital image correlation method (DIC) and finite element method (FEM). The joints were consisted of four drift-pins. The distribution of the strain perpendicular to grain and the shear strain parallel to the grain were examined around each drift-pin to evaluate the large deformed area and the location of initial failure. Results were as follows.Areas of large compression strain perpendicular to the grain and large shear strain were observed in the predicted loading area of each drift-pin. Large tensile strain perpendicular to the grain was observed at the area close to the loading (contacting) area of the drift-pins, and the tension area was partly overlapped with the area of large shear strain. The overlapped area coincided with the location of initial cracks propagated parallel to the grain. This coincidence suggested that the cracks occurred by mixed-mode fracture in this joints. The numerical results by finite element analysis were compared with the experimental results obtained with DIC and they gave good agreement with each other.
Unsatisfactory lateral resistance of nailed shear walls mainly results from low lateral resistance of the nailed joints between sheathing and frame members. Among the factors reducing the lateral resistance of the nailed joints are insufficient. end or side margins. In the previous paper, unavoidable human irregularity in nailing on construction sites was considered as a principal cause of insufficient margins. In this paper, we focused on another cause of insufficient margins, bow of frame members.Monte Carlo simulations were conducted to estimate the influence of bow of frame members and human irregular nailing on the effective resistance of nailed shear walls. In the Monte Carlo simulations, two assumptions were adopted. The first assumption was that the insufficient margins of the nailed joints were caused only by the bow. The second assumption was that the insufficient margins of the nailed joints were caused by both the bow and human irregularity.The simulations with the first assumption showed that the effective ratio of lateral resistance of nailed shear walls may be estimated in practice as 0.95 of the ideal resistance. The simulations with the second assumption showed that the effective ratio of lateral resistance of nailed shear walls may be estimated in practice as 0.80less than or equal to (effective ratio) <0.95 of the ideal resistance considering the reliability of process control of construction works or production of shear walls.
To clarify the relationships between moisture content and the dielectric constant of wood, the complex dielectric constant epsilon* of water saturated sugi and hinoki wood was measured in the frequency range from 1 MHz to 1.8 GHz at room temperature (20degreesC). The dielectric constant epsilon' and loss C in the longitudinal (L) direction for sugi and hinoki woods were slightly lager than those in the tangential (T) and radial (R) direction. The dielectric constant epsilon' and loss epsilon" were measured during drying from water-saturated condition at 20degreesC and 65%RH. The e' during drying in L-direction was larger than that in T-direction. The slope of the curve relating epsilon' and moisture content was different in each of the moisture content ranges of 0 to 50%, 50 to 100%, and 100 to 250%. The effect of frequency on E, was not distinct in the moisture content from 0 to 250%. In the frequency range from 1MHz to 1.8 GHz, there were high correlations between moisture content and epsilon' or epsilon'.
Rhamnogalacturonan II (RG-II) is a low molecular weight, structurally complex pectic polysaccharide present in the primary cell walls of plants. RG-II is covalently linked to homogalacturonan. RG-II exists predominantly in the cell walls as a dimer (dRG-II-B) that is cross-linked by a 1: 2 borate-diol ester. Borate ester cross-linking of pectin would be required for the stabilization of cell walls and normal growth of plants. dRG-II-B specifically binds metal ions, such as calcium, strontium, barium and lead. The functions of these metals present in dRG-II-B are also discussed.
Spruce wood specimens were steamed at 120-180degreesC and their equilibrium moisture content (M) was compared with that of wood heated in the absence of moisture. Steaming gave larger losses in weight of wood (WL) than dry heating at the same temperature and duration. At low relative humidity (RH) (less than 57%), no reversible effect was recognized in the M of steamed wood while the M of wood heated dry recovered considerably after moistening. At 97% RH, the M of steamed wood was higher than that of wood heated dry at the same WL. The higher M value of the steamed. wood was attributed to the hygroscopic nature of depolymerized hemicelluloses remaining in the wood. However, the M of the steamed wood was still higher than that of the wood heated dry, even after the removal of hygroscopic water-soluble substances. The water sorption isotherms of unheated and heated wood were analyzed by using the Hailwood-Horrobin adsorption equation. At the same WL, steaming and dry heating had the same effect on the reduction of hydrated water. On the other hand, steaming showed less effect on the reduction of dissolved water than dry heating. In addition, the amount of dissolved water increased by steaming to a 5% WL. It was speculated that steaming loosened the binding structure of the wood cell wall to increase the dissolved water, whereas dry heating tightened the cell wall structure to restrict moisture sorption and swelling of the cell wall components.
This paper deals with the properties of gypsum-bonded particleboard as related to its manufacturing conditions. The effects of press time, wood/gypsum weight ratio, water/gypsum weight ratio, and resin content on the properties of gypsum-bonded particleboard were investigated. The results obtained sere as follows : the press time can be shortened to 1.5 h for weight ratios of wood particles to gypsum dihydrates of 1/5, and for weight ratios of wood particles to gypsum dihydrates of 1/3 by the addition of water based polymer-isocyanate adhesive resin. The mechanical properties reached a maximum when the water gypsum hemihydrate ratios were in the range of 0.35-0.40 with particle to gypsum dihydrate ratios of 1/3 and 1/4. The additional of water based polymer-isocyanate adhesive resin improved the mater resistance of both the mechanical and dimensional properties of gypsum- bonded particleboard.
