Mechanical Performance of Sugi (Cryptomeria japonica) Wooden Frame-Construction Lumber and Evaluation of Stress Grading

Various strength performances (bending, tensile, compression and shearing) of wooden frame- construction lumber (204, 206) sawn from sugi logs grown in southern Miyazaki were examined. Based on the result, stress grading using modulus of dynamic elasticity was conducted, and its necessity and effectiveness were compared with visual grading. With visual grading, select structural amounted to 80% in 204, and to 93.3% in 206. Also, the 5% lower limit of sugi exceeded the characteristic value of S-P-F second class, which mainly consist of dimension lumber, except for tensile strength of 206. Moreover, it was suggested that the stress grading method should be more effective than visual grading. It is thought that the structural calculation can be adapted to sugi by this scrutinized method equally to S-P-F. Therefore, if members which are adapted to the stresses of each location can be used effectively, it will be expected to increase the use of sugi significantly.