BENDING PERFORMANCE OF SUGI (CRYPTOMERIA JAPONICA) LUMBER SAWN PARALLEL TO THE EDGE OF LARGE DIAMETER LOGS

摘要

Material characteristics of large diameter sugi logs grown in Miyazaki and flat squares sawn from them were investigated and their bending performances were examined. Modulus of elasticity from longitudinal vibration (E_t) of first logs was about 19% lower than that of second logs. However, modulus of rupture in bending (MOR) was only 2% different between lumber without pith sawn from first logs by taper rule sawing and lumber with pith sawn from second logs by center rule sawing, and the difference was not significant. In relationships between E_t of logs and E_t of flat squares, E_t increased only 2% for lumber with pith obtained from second logs, while E_t increased 25% for lumber without pith obtained from first logs. It shows that taper rule sawing is an effective method to improve the bending performances.