In this study, with the view to using effectively small and medium diameter Korean domestic woods as structural materials, cross-laminated woods were manufactured by using six species of Korean domestic softwoods and hardwoods, and bending creep properties were investigated for each species. The cre...
In this study, with the view to using effectively small and medium diameter Korean domestic woods as structural materials, cross-laminated woods were manufactured by using six species of Korean domestic softwoods and hardwoods, and bending creep properties were investigated for each species. The creep curves showed the shape of the exponential function plot, and the creep curves after 1 hour were able to estimate by fitting it to the power law. The initial and creep compliances of cross-laminated woods showed the higher values in wood species with a low density than in that with a high density. And by cross-laminating, the initial and creep compliances perpendicular to the grain considerably decreased, the extent of the decrease was found to be greater in creep deformation than in initial deformation. The creep anisotropies of cross-laminated woods were considerably decreased by cross-laminating. The relative creep of $C_{\bot}$ type composed of perpendicular-direction lamina in the faces decreased 0.59 - 0.64 times compared to that of $P_{\bot}$ type composed of perpendicular-direction laminae in all layers, and that for $C_{\parallel}$ type composed of parallel-direction laminae in the faces increased 1.5 - 1.6 times compared to that of $P_{\parallel}$ type composed of parallel-direction laminae in all layers.
In this study, with the view to using effectively small and medium diameter Korean domestic woods as structural materials, cross-laminated woods were manufactured by using six species of Korean domestic softwoods and hardwoods, and bending creep properties were investigated for each species. The creep curves showed the shape of the exponential function plot, and the creep curves after 1 hour were able to estimate by fitting it to the power law. The initial and creep compliances of cross-laminated woods showed the higher values in wood species with a low density than in that with a high density. And by cross-laminating, the initial and creep compliances perpendicular to the grain considerably decreased, the extent of the decrease was found to be greater in creep deformation than in initial deformation. The creep anisotropies of cross-laminated woods were considerably decreased by cross-laminating. The relative creep of $C_{\bot}$ type composed of perpendicular-direction lamina in the faces decreased 0.59 - 0.64 times compared to that of $P_{\bot}$ type composed of perpendicular-direction laminae in all layers, and that for $C_{\parallel}$ type composed of parallel-direction laminae in the faces increased 1.5 - 1.6 times compared to that of $P_{\parallel}$ type composed of parallel-direction laminae in all layers.
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제안 방법
In this study, in addition to the previous study, 24 types of parallel- and cross-laminated woods were manufactured using six Korean domestic woods, and bending creep test was performed, and the influence of wood species on creep property was investigated.
대상 데이터
Six species of Korean domestic woods were selected for this study. They included three softwoods: Japanese cedar, Japanese cypress and Japanese larch; three hardwoods: chestnut, tulip tree and oriental oak.
And C∥ type (C∥(S), C∥(H), C∥(L), C∥(C), C∥(T) and C∥(O)) and C⊥ type (C⊥(S), C⊥(H), C⊥(L), C⊥(C), C⊥(T) and C⊥(O)) were the specimens used to measure the bending creep parallel and perpendicular to the grain of the face laminae of cross-laminated woods, respectively. There were 3 of each type of specimen, for a total of 72 specimens.
성능/효과
1) The creep curves showed the shape of exponential function plot which was sharply increased at upper right side, and the extent of the increase was higher in softwoods with low densities than in hardwoods with high densities. The creep curves showed a curvilinear behavior for about 30 minute to 1 hour after loading, but then showed a linear behavior.
2) The initial and creep compliances for cross-laminated woods were greatest in that made with Japanese cedar having a low density, and were lowest in that made with oriental oak having a high density.
3) By cross-laminating, initial and creep compliances of parallel-laminated woods (P⊥ type) composed of perpendicular-direction laminae in all layers considerably decreased, and the extent of the decrease was greater in creep deformation than in initial deformation.
4) The creep anisotropies expressed as ratios of creep compliance perpendicular to the grain of face laminae versus that parallel to the grain of face laminae of laminated woods were 1: 0.54-0.86 for initial deformation, and 1: 0.28-0.67 for creep deformation. By cross-laminating, the values were markedly decreased, and the extent of the decrease was found to be greater in creep deformation than in initial deformation.
As a results, the bending strength performances increased with the densities of wood species, and the anisotropy was markedly reduced by cross-laminating, and the bending strength performances perpendicular to the grain markedly improved. Also, the ratios of the measured values to the estimated values were almost similar in the cross-laminated woods with perpendicular-direction laminae in the faces, but it was very great in the cross-laminated woods with parallel-direction laminae in the faces. This was considered due to the effects of deflection caused by shear forces as the results of various cross-laminated woods manufactured with several wood species studied for many years by the authors (Park et al.
, 2016), with a view to effectively use small- and medium-diameter Korean wood as structural materials, cross-laminated woods were manufactured using six species of Korean softwoods and hardwoods, and static bending strength performances were investigated. As a results, the bending strength performances increased with the densities of wood species, and the anisotropy was markedly reduced by cross-laminating, and the bending strength performances perpendicular to the grain markedly improved. Also, the ratios of the measured values to the estimated values were almost similar in the cross-laminated woods with perpendicular-direction laminae in the faces, but it was very great in the cross-laminated woods with parallel-direction laminae in the faces.
The creep compliances were in order of P⊥(S) > P⊥(L) > P⊥(H) > P⊥(C) > P⊥(T) > P⊥(O). It was found that cross-laminated woods made with softwoods were higher than those made with hardwoods on the whole, and their values showed the density dependence. The initial compliances of P⊥ type were 5.
3 shows typical examples of creep curves of parallel- and cross-laminated woods made with domestic six species. The creep curves showed the shape of the exponential function plot which markedly increased at upper right side with the increase of time, and the extent of the increase was higher in the laminated woods made with Japanese cedar with the lowest density than in that made with oriental oak with the highest density of the tested species. It was found to be higher in softwoods than in hardwoods.
The initial compliance showed 0.69 - 0.87 times lower than that of P⊥ type, and the creep compliance showed 0.39 - 0.64 times lower than that of P⊥ type, both the initial and creep deformation was considerably decreased by cross-laminating, and the extent of the decrease was found to be markedly higher in creep deformation than in initial deformation.
The values were in order of C∥(S) > C∥(L) > C∥(H) > C∥(T) > C∥(C) > C∥(O). The initial compliance showed 1.0 - 1.3 times higher than that of P∥ type, and the creep compliance showed 1.1 - 2.6 times higher than that of P∥ type, both the initial and creep compliances were increased by cross-laminating, and the extent of the increase was found to be higher in creep deformation than in initial deformation. As shown in Fig.
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