STRENGTH PROPERTIES OF SUGI (CRYPTOMERIA- JAPONICA) GROWN IN AKITA PREFECTURE .1. YOUNGS MODULI OF LOGS

Mechanical properties of sugi (Cryptomeria japonica) grown in Akita Pr efecture were tested in logs, lumber, and glued laminated timbers. The aims of the study were to develop a stress grading system based on th e modulus of elasticity and to consider application of sugi lumber to glulam for structural use. In this study, the dynamic moduli of elasti city by longitudinal vibration (E(fr)) were measured for 1,075 logs fr om 19 stands. Differences in E(fr) among stands and among trees were s ignificant at the 1% level. Variations were decreased considerably whe n the timber was classified by these categories; Although differences between first logs and second logs also were significant, differences between first logs and upper logs were not significant because of larg er variations among the latter. The average E(fr) of all stands was fo und to be as large as 8.13 GPa. The large amount of mature wood contai ned in the logs due to the advanced stand ages of 54 to 86 years seeme d to cause this result.