Drying schedules for timber have been decided depending on research effort and experience of the dryer's operators. When they encounter drying conditions that are new and/or outside of prior experience, they should find the optimal method to dry timber sufficiently. We think that we can help them to find the optimal schedule by setting up a drying time calculation method based on heat and mass transfer theories. In this study, we focused on high drying temperature above the boiling point, we divided the high temperature drying process into 4 phases, and applied different models for each phase. Approximate data of thermo physical properties for those calculations was obtained from valuable references of the past.

View full abstract

To study the influence of whorled knots on the bending strength of Japanese red pine (Pinus densiflora) two-side-surfaced beams, static bending tests were conducted for each visual grade specified by the Japanese Agricultural Standard for lumber. Rectangular beams were also tested for comparison. The influence of whorled knots on bending strength was less for two-side-surfaced beams than rectangular beams, and the maximum load of two-side-surfaced beams was significantly higher than that of rectangular beams of low visual grade. Based on the experimental data, the estimated maximum load ratios of two-side-surfaced beams to rectangular beams were 1.59, 1.62, and 1.95 for visual grade I, II, and III, respectively, when both beams were sawn from 300mm-diameter logs. It was shown that the two-side-surfaced beams had more advantages than rectangular ones in regard to efficient use of logs with identical diameter.

View full abstract

The wedged and halved scarf joint, Okkake-tsugi, is one of the Japanese traditional wood joints. In the process of bending failure, a cleavage fracture is observed by friction force at the butt end of the joint. According to the failure, it is supposed that one of the factors determines the yielding of joints. After splitting failure of the butt end, because of increasing displacement and because the assumption of the Navier hypothesis no longer holds, it is necessary to estimate the load at cleavage fracture by friction force at the butt end in order to predict the load-deformation behavior at the joint and the subsequent yield. In this study, we experimented to reproduce the pseudo shear force due to friction force on the butt end. We made clear the relationship between loads at cleavage failure and factors at splitting, to extract the factors that affect the expected cleavage fracture load. We also tried to formulate a general equation, and reported that the results were examined for their applicability.

View full abstract

Hinoki (Chamaecyparis obtusa), a Japanese native conifer is an important tree as timber for temples and shrines. Taiwan hinoki (C. obtusa var. formosana), a Formosan native, is a close relative of hinoki, and had been used as its substitute before Taiwan's ban on harvesting in 1992. Since Taiwan hinoki was used for restoration of many old wooden buildings, identification of the two species as timber is important in historic studies. Distinction of the two species, however, is known to be difficult by mere anatomical examination. Here we attempted chemical identification of a wood specimen from a university gate weathered for over 70 years. While neither GC/MS of volatile components nor qualitative analysis of hinokitiol could determine the species, thin-layer chromatography (TLC) of the dichloromethane extract by silica gel plate combined with fluorescence fingerprinting was found effective for distinguishing the two species. The results showed that the wood of the old gate is C. obtusa var. formosana. This technique of TLC fingerprinting is potentially useful in chemotaxonomical identification of wood species in general.

View full abstract

This report presents theoretical examination of three methods for bending stress analysis of symmetrical two-layered simply supported beams with incomplete interaction. The methods were Newmark's theoretical method, Kamiya's numerical calculation method and Kamiya's approximation method. In order to simply calculate deformation of the beam by Newmark's method, equations of relationship between the deformation and stress of the beam were developed. Kamiya's numerical calculation method was improved for accuracy and stability. In order to compute the value of stress, the approximation was improved. Numerical examinations were conducted. The validity of the approximation method was confirmed. The relationship between the number of shear connectors and error in deflection calculated by Newmark's method was obtained.

View full abstract

In order to discuss how adhesive strength at elevated temperature affects the fire resistance of glued laminated timber (GLT), structural GLT beams using adhesives of phenol-resorcinol-formaldehyde (PRF) resin, aqueous polymer isocyanate (water based polymer-isocyanate, API) resin or polyvinyl acetate (PVAc) resin were made and their fire performances were evaluated. The PRF-GLT beams and API-GLT beams exhibited the fire performance required for the 45-minute fire test. However, the PVAc-GLT beams failed to withstand the fire test because the laminae separated earlier than PRF-GLT and API-GLT. The adhesive shear strengths in laminated wood at elevated temperature were evaluated. They decreased with rising temperature, and were found to be RF > API > PVAc at 100°C, 150°C and 200°C. In particular, PVAc decreased drastically, where the adhesive strength at 150°C was almost null. The fire resistance degradation of GLT beams is dominated by the loss of laminae, and depends on the adhesive shear strength in laminated wood. If the adhesive shear strength at 200°C is enough to keep laminae from separating, the GLT beam specimens are expected to exhibit 45-minute quasi-fireproof performance.

View full abstract