남부지역 삼나무 간벌목재의 못접합특성과 할렬발생

The Nail Jointing Properties and Checking Mechanism of Thinned Japanese Cedar (Cryptomeria japonica D. Don.) Boards Grown in Southern District

This experiment was carried out to investigate the effects of nail diameter, driving dis-tance from end on the nail check length, and the effects of nail diameter, prehole for nail driv-ing, and nail driving slope on the nail withdrawal resistance, by the static test of universal test-ing machine. The test specimen were Japanese cedar (Cryptomeria japonica D. Don.) boards grown in southern district of Korea, and the nails for test were 2.02～4.82 mm in diameter. After nail driving, the back face checks of test boards were longer than the surface checks. The optimum nail diameter without checks or loss of nail withdrawal resistance were below 10% of board width and the optimum driving distance from end of boards were ten multiple of nail diameter. The relation between nail diameter (x) and withdrawal resistance (y) was linear and the regression formulae for Japanese cedar board was y = 8.66x + 7.6 (R2 = 0.978). As both of the prehole diameter and driving slope were increased, the withdrawal resistances were sig-nificantly decreased.