Estimation of snowload required to cause stem failure in Boka-sugi [land variety of Cryptomeria japonica] stand
1988
Kato, A.(Toyama-ken. Forestry and Forest Products Research Center, Imizu (Japan)) | Nakatani, H. | Taira, H. | Aiura, H.
The snow damage of trees was considered as a failure of tapered column receiving an eccentric compressive load of snow accumulated on an asymmetric crown, and then the snowloads to cause breakage stem for 18 damaged trees in 25-year-old Bokasugi (Cryptomeria japonica D. DoN) stand were estimated. In the absence of the lever arm (the horizontal displacement of the center of gravity of snowloaded crown from the stem axis), the snowload for each sample tree may be calculated from a buckling load of the stem. The buckling load was calculated using measured the stem forms, the mechanical properties of the wood, and the micro-value, which indicated the resistance of the roots to the turning moment. The DBH, the height, the modulus of elastisty of the wood and micro-value for the sample trees were on average 26.6cm, 20.5m, 49400kgf/square cm and 1.43 x 10E-7 rad/kg.cm, respectively. The loading point for each damaged tree was assumed to be at 78% of the tree height, equivalent to the mean of the center of gravity of the crown obtained from the another samples. The mean snowloads required for the failure were estimated at 486kgf. The influence of the lever arm (e) to the snowload causing stem breakage was investigated. The result showed that the lever arm reduced the snowload by 14% if e=50cm, and by 26% if e=100cm.
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