Reverberation tends to increase with the acoustic reflection at the rectangular interior surface of reinforced concrete buildings and often should be controlled by using sound absorbing materials and structures. Fibrous and porous materials can be used to absorb sound at the relatively high frequency range, but some kind of sound absorbing structures are needed in order to suppress reverberation at the low frequency range of less than ca. 200Hz. In this research, we fabricated wood slit panels and clarified their sound absorbing performance as functions of their dimensions and the layout of sound absorbing materials inserted in the air space behind the slits. Moreover, we made clear that sound absorbing performances of sawdust and wood fibers were equal to those of sound absorbing materials on the market. These results lead to develop sound absorbing wood based interior panels, and also promote wood interiors of public buildings.

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Wooden frame construction with Large Finger Joints (LFJ) for intermediate member types could be available for middle-rise buildings. The structural performance of this construction would depend on the performance of the intermediate members. In this paper, a plywood laminated component of Karamatsu (Larix kaempferi) was used as the intermediate member. Bending tests of plywood for the vertical direction, shearing tests of plywood and joint efficiency tests of LFJ connecting plywood components with glulam of Karamatsu were conducted to obtain several values to estimate the performance of full scale T-shaped and L-shaped joints. Full scale joint tests showed that the ultimate failure occurred on the LFJ on the plywood component's side. Applying a design method for connections in steel structures to this joint, the estimated strength of the plywood component for shearing was higher than that of LFJ for bending, even though it would have a larger plywood component for heavier timbers. The allowable strength of this joint system could be evaluated from the bending strength of the LFJ of the plywood component.

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We evaluated the adhesive properties of plywood used as floor sheathing (Concrete form plywood, tropical wood, 12mm thickness, type 1 according to Japanese Agricultural Standard for plywood) extracted from nine houses in Hokkaido. Furthermore, we examined adhesive properties of new control plywood after accelerated aging treatments, and we compared its deterioration with the effects of actual use. In the accelerated aging tests by cyclic boiling, shear strength and wood failure decreased as the number of boiling cycles increased. Before this treatment, a clear positive correlation was observed between the density and the shear strength of the control plywood; however, the correlation was diminished due to the treatments. That is to say, high-density plywood tended to be more deteriorated than low-density plywood. The retention of shear strength of the used plywood, which was estimated on the basis of the shear strength of the new control plywood, decreased as the density of the plywood increased. This tendency agreed with the results of the accelerated aging tests of the control plywood. These results showed a practical possibility of durability assessments of structural plywood by converting the number of boiling cycles in the accelerated aging tests into equivalent periods of actual use.

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