Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title><jats:p>Cellulose is synthesized by organisms belonging to each biological kingdom, from bacteria to terrestrial plants, leading to its global-scale distribution. However, the structural properties of cellulose, such as its microfibril size, crystal form, cross-sectional shape, and uniplanar orientation, vary among species. This mini-review discusses the structural properties and diversity of cellulose. After describing historical developments in the structural analysis of cellulose, the technique of intracrystalline deuteration and rehydrogenation to understand structural diversity—particularly the localization of crystalline allomorphs in single microfibril—is discussed. Furthermore, the development of cellulose materials that maintain hierarchical structures of wood is introduced, and methods for producing functional materials are presented.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Four kinds of glued laminated timber were produced (i.e., one with a glued edge-joint and the other three with nonglued edge joints) in the lamina at different positions toward the depth direction. Shear tests using an asymmetric four-point bending method were then conducted for these glued laminated timber specimens. The results showed that although the glued edge-joint specimens had the highest shear strength in all groups, the shear strength decreased as the distance from the adjacent nonglued edge-joint plane decreased. Furthermore, the shear strength of all specimens exceeded the standard shear design strength value (2.1 N/mm<jats:sup>2</jats:sup>) set by the Ministry of Land, Infrastructure, Transport and Tourism, Japan. Next, the shear strength of the nonglued edge-joint specimens was estimated based on that of the glued edge-joint specimens. Although the mean-estimated shear strength was lower than the mean-measured shear strength, the possibility of the shear strength changing based on the position of the nonglued edge-joint plane specimens from that of the glued edge-joint specimens was still estimated.</jats:p>

<jats:title>Abstract</jats:title><jats:p>The embedment properties of the dowel-type fasteners is a fundamental parameter that can determine the shear resisting performance of the connections utilized in cross-laminated timber (CLT) structures. To investigate the embedment strength of the smooth dowels inserted in CLT narrow side, totally 504 CLT embedment specimens were tested to evaluate the effects of the influencing factors on the embedment strength, which included the loading angle, the embedment angle, the embedment position, the diameter of the dowels, and the gaps between the lumbers. The existing predictive equations of the embedment strength were validated based on the experimental results, and modified empirical equations were proposed for a more accurate prediction on the average embedment strength. It is found that when the loading direction with a loading angle of 90 degree is parallel to the adhesive layer, for the dowels embedded in the core layer and for those embedded between layers, the average embedment strength decreases by 27.89% and by 33.61% with an increase of the diameter from 8 to 24 mm, respectively. When the loading direction is perpendicular to the adhesive layer, the average embedment strength of the smooth dowels with an embedment angle of 90 degree is 85.25–218.96% higher than that of the dowels with an embedment angle of 0 degree. Furthermore, almost no drop can be identified for the embedment strength of the dowels with an embedment angle of 0 degree when the gap exists in their embedment position. A more accurate prediction on the average embedment strength can be achieved based on the modified empirical equations.</jats:p>

<jats:title>Abstract</jats:title><jats:p>This study investigated the interaction between particle size and mixing ratio on the porosity of particleboard and in consequence its effect on the physical and mechanical properties of panels. Tea Oil Camellia Shell (TOCS), which could provide 1.8 million tons of lignocellulose raw material annually, can be a useful resource for particleboard production. In that regard, particleboards with different particle sizes (coarse and fine) and mixing ratios (wood and TOCS) bonded with Polymethylene polyphenyl polyisocyanate (pMDI) were investigated. The results showed that particleboard made with TOCS particles had higher densities than those of commercial wood particles. Furthermore, particleboards made with fine particles had lower porosity. The average values for physical and mechanical properties have shown that except for thickness swelling (TS), most properties were better with coarse particles. In terms of all properties, results showed that adding 50% of commercial wood in conjunction with TOCS particles regardless of particle size can offer acceptable results, which qualified all requirements of EN 312:2010 standard for P2-type particleboard (boards for interior fitments (including furniture) for use in dry conditions). In addition, due to the porous structure of the shells, TOCS-based particleboards have better thermal conductivity compared to wood-based particleboards.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Evaluations of the lateral properties of timber joints are necessary to ensure the safety of timber buildings. The yield load is an important property that is usually obtained using authorized engineering techniques. Although yield loads have been easily obtained using authorized techniques, events that have occurred in the joint during yielding have not been clarified. This study experimentally obtains elastic limit data using nailed joints. Mechanical tests measuring the residual displacement after various lateral loads with six-joint specimen specifications were conducted. In this study, the load at which the residual displacement reached 5% of the nail diameter was defined as the elastic limit. The experimentally obtained elastic limits were compared with the yield loads obtained using authorized engineering techniques. The ratios of elastic limits to the yield loads obtained using the perfect elasto-plastic model, method described in EN, and 5% offset method were 0.554–0.743, 0.557–0.834, and 0.648–0.801, respectively. The results numerically revealed that residual displacements occurred at a much lower load than the yield loads.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Dou-gong is an essential part of traditional timber buildings in East Asia, having a decoration function and a load transfer function. The San-dou component, which is vulnerable to the lateral push force of the Gong, Fang, and purlin, is a critical structural component in the Dou-gong. In San-dou components, there are two distinctive types of surfaces subjected to lateral push force, perpendicular to the grain and parallel to the grain. However, few investigation into the structural performance of these two types has been done. Considering this shortcoming in the literature, in the current study, tests were carried out to obtain elasticity and strength characteristics on 90 timber specimens of fir and larch. After the material property test, 24 San-dou specimens were prepared to investigate the lateral push resistance. Consequently, an elastic–plastic damage assessment model was developed to calculate the load–displacement curve and possible damage distribution region of San-dou component, using the nonlinear finite-element analysis. According to the analyses, the failure mode for the San-dou component perpendicular to the grain is a horizontal crack parallel to the Dou-ear. Besides, the failure mode of the San-dou component parallel to the grain is an oblique crack, which begins from the inner edge of the Dou-ear to the lower part of the San-dou component. In the case of the other factors being the same, the bearing capacity of the larch San-dou component is 49.64–55.78% stronger than the fir San-dou component. Besides that, the bearing capacity of the San-dou component perpendicular to the grain is 32.85–38.22% higher than the San-dou component parallel to the grain. The research findings are expected to give a theoretical foundation for the structural evaluation of the Dou-gong system in traditional timber buildings and a scientific basis for elucidating the differences in the construction of traditional timber buildings in East Asia.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Radial bamboo strips are being widely used for structural applications due to the higher yield and high strength. However, there was a sharp taper at the top of bamboo which made nodal diaphragm removed incompletely during the process of stripping. The residual bump could bring about poor bonding strength between adjacent radial bamboo strips. In addition, the traditional radial bamboo strips should be weaved before the next step of processing, which caused a lot of material wastes and consumed a lot of labor and time. In order to address these problems, a novel lumber product made of laminated radial bamboo slices was developed by the proper arrangement of core layer and surface layer. The major and minor directions of a panel were defined as the parallel- and perpendicular-to-its arrangement ones in the core layer, respectively. It was found that (1) the layups with double-layer bamboo mats and radial bamboo slices could produce better mechanical properties. The effective modulus of elasticity in major and minor direction was about 7032.5 MPa and 5016.0 MPa, respectively. The effective modulus of rupture in major and minor direction was about 81.0 MPa and 43.6 MPa, respectively; (2) the density distribution tended to be uniform, with a density of about 0.7 g/cm3 that was lower than other similar bamboo-based materials (about 1.0 g/cm3); and (3) the failures occurred in bamboo slices rather than along the bond lines, suggesting good bond quality achieved in this study.</jats:p>

<jats:title>Abstract</jats:title><jats:p>A vibration test to measure the mass of a specimen without weighing it using the difference between the resonance frequency with an additional mass and that without it (vibration method with additional mass, VAM) was applied to small, clear, and wooden specimens assuming practical situations. An apparatus that provided various end conditions by compressing the ends of the specimens was used in the tests. Bending vibration tests were performed on the specimens installed in the apparatus with/without an additional mass. Because the mass ratio (estimated mass by VAM/measured mass), namely, <jats:italic>M</jats:italic><jats:sub>VAM</jats:sub>/<jats:italic>M</jats:italic><jats:sub>0</jats:sub>, which represents the estimation accuracy of VAM, was stable when the compressive strength was sufficiently large, VAM could be adequately used when the specimen was properly installed in the apparatus. The end condition at maximum compressive stress by the apparatus was an imperfect fixed condition. The <jats:italic>M</jats:italic><jats:sub>VAM</jats:sub>/<jats:italic>M</jats:italic><jats:sub>0</jats:sub> value greatly deviated from 1 in the specimens with a large height. The deviation in <jats:italic>M</jats:italic><jats:sub>VAM</jats:sub>/<jats:italic>M</jats:italic><jats:sub>0</jats:sub> from 1 was due to the introduction of the measured resonance frequencies with/without a concentrated mass into the frequency equation that required resonance frequencies under an ideal fixed–fixed condition. A correction method for <jats:italic>M</jats:italic><jats:sub>VAM</jats:sub>/<jats:italic>M</jats:italic><jats:sub>0</jats:sub> was then proposed.</jats:p>

<jats:title>Abstract</jats:title><jats:p><jats:italic>Pterocarpus santalinus</jats:italic> and <jats:italic>Pterocarpus tinctorius</jats:italic> are commonly used species of the genus <jats:italic>Pterocarpus</jats:italic> in the wood trade. Although both of them have been listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) since 2019, it is still critical to identify them in terms of plant taxonomy. Currently, high-temperature heating is an accepted treatment method for high-density wood species such as <jats:italic>Pterocarpus</jats:italic> to improve dimensional stability and restore previous drying defects partially. It has proved challenging to identify the high-temperature (e.g., 120 °C) heated wood from these two species. Thus, this study approaches species identification of two <jats:italic>Pterocarpus</jats:italic> of high-temperature (e.g., 120 °C) heated solid wood samples using headspace–gas chromatography–mass spectrometry (HS–GC–MS). Besides, a computational analytical method named similarity network fusion (SNF) was proposed to aggregate data in two different types, respectively, derived from the HS–GC–MS and direct analysis in real time–mass spectrometry (DART–MS) to explore the feasibility of improving the efficiency and accuracy of wood species discrimination. The SNF exhibits more significant differences and higher predictive accuracy (100%) between <jats:italic>P. santalinus</jats:italic> and <jats:italic>P. tinctorius</jats:italic> than that based on the HS–GC–MS data (77.78%) or DART–MS (66.67%) alone. These results demonstrated the capability of the HS–GC–MS technique in the analysis of high-temperature heated solid wood and the potential of multidimensional or comprehensive data sets based on the SNF algorithm in the field of wood species identification.</jats:p>

<jats:title>Abstract</jats:title><jats:p>To explore in-plane shear failure mode of cross-laminated timber (CLT) panel, this paper carried out relevant research work from the perspective of stress analysis and combined with the crack morphology of the specimen after planar shear. In this study, the load–displacement curve of the hemlock [<jats:italic>Tsuga canadensis</jats:italic> (L.) Carrière] CLT specimen was obtained by a three-point bending test or an improved planar shear test, the crack morphology of the CLT vertical layer and the azimuth angle of the crack surface were observed and recorded synchronously. The shear strength values of CLT specimens under the two tests were obtained by corresponding calculation. Then the stress analysis of the CLT vertical layer was combined with the azimuth angle of the crack surface to discuss the failure mode of the CLT vertical layer in planar shear. The results showed that the planar shear strength measured by the three-point bending test and the improved planar shear test was in good agreement, and the results measured by the improved planar shear test were more dispersed than those measured by the three-point bending test; Considering the approximation that the in-plane shear of the CLT vertical layer could be treated as pure shear, the three-point bending test was better than the improved planar shear test; For the vertical layer of 63.3% CLT specimens, the azimuth of the crack surface was near the azimuth of the first principal plane obtained by stress analysis; There were two failure modes in the CLT vertical layer in-plane shear: tension failure and shear failure.</jats:p>