Studies on improving mechanical properties and effective application for beams of flat squares obtained from lower part of sugi logs

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(1) Mechanical properties of flat squares sawn from sugi large diameter logs were examined. As a result, it was clarified that the lumber without pith sawn from first logs by taper rule sawing has almost the same properties as lumber with pith sawn from second logs by center rule sawing. (2) In order to clarify the properties of sugi sawn lumber obtained from curved logs, some evaluation tests were carried out. The result showed that, as far as the logs with maximum curved rate of about 1-2% go (so-called “B-zai”), there is almost no practical barrier to pick out them for beams considering the warp due to sawing and drying, bending strength, and creep deflections.