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題 名 | 栽植距離對柳杉強度變異之影響(2)--動彈性係數與靜彈性係數=Effects of Plantation Spacing on the Strength Variation of Japanese Cedar(Ⅱ)--Dynamic and Static Modulus of Elasticity |
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作 者 | 卓志隆; | 書刊名 | 林產工業 |
卷 期 | 19:1 2000.03[民89.03] |
頁 次 | 頁9-22 |
分類號 | 474.3 |
關鍵詞 | 柳杉; 栽植距離; 振動試驗法; 動彈性係數; 靜曲性質; 機械應力分等; Japanese cedar; Plantation spacing; Vibration method; Dynamic modulus of elasticity; Bending strength properties; Machine stress rated; |
語 文 | 中文(Chinese) |
中文摘要 | 本研究之柳杉試材取自溪頭實驗林區40年生之立木,以振動法探討五種不同栽植距離之無缺點小試材,在生材及氣乾(平均含水率為16%)狀態下之彎曲及縱向動彈性係數之差異。並由縱向動彈性係數與靜曲破壞強度間之關係,建立柳衫機械應力分等等級。本研究得到如下結果:1. 各栽植距離間之動彈性係數存在顯著差異性,以動彈性係數考量材質,溪頭地區柳杉造林木之最適栽植距離為1 m×1 m,最不理想的距離為5 m×5 m。2. 溪頭地區生產之柳杉值得國內推廣使用於木結構上。3. 動彈性係數與靜曲破壞強度間存在極顯著之線性關係。以縱向動彈性係數為機械應力分等依據,分為E5、E7、E9、E11、E13、E15等六個等級之靜曲容許應力值如表9所示。4. 在氣乾及生材狀態時,柳杉彎曲動彈係數較靜曲彈性係數分別大約14%及38%。5. 柳杉動彈性係數受含水率的影響較靜曲彈性係數為小。6. 動彈性係數與柳杉之絕乾密度具有顯著的相關性。 |
英文摘要 | 40-year old Japanese cedar (Cryptomeria japonica D. Don) sample trees were collected from Chi-Tou (in central part of Taiwan), the Experimental Forest of National Taiwan University. Flexural and longitudinal dynamic moduli of elasticity for small, clear specimens from five plantation spaceings have been evaluated by vibration technique. Machine stress rated lumber of Japanese cedar was established by using relationship between longitudinal dynamic modulus of elasticity and bending strength. The following conclusions can be drawn from this study: 1. Difference in dynamic moduli of elasticity among five plantation spacings were significant at the 5% level. From the viewpoint of dynamic mechanical properties, proper plantation spacing of Japanese, cedar planted tree was 1×1 m, while 5×5 m was not suitable. 2. It is recommended that Japanese cedar growing in Chi-Tou can be used as structural member in domestic wood construction building. 3. Bending strength of test specimens can be predicted well from the dynamic moduli of elasticity, based on the results of significant linear relationship at 1% level. Machine stress rated grade classification for Japanese cedar lumber by longitudinal moduli of elasticity are E5, E7, E9, E11, E13, E15,and the corresponding allowable bending stress values are shown in table 9. 4. Flexural dynamic moduli of elasticity of Japanese cedar under green and air dry conditions were 38% and 14%, higher than those of static moduli of elasticity. 5. Dynamic moduli of elasticity was less affected by moisture content than static moduli of elasticity. 6. There was a significantly positive relationship between oven dry density and dynamic moduli of elasticity at 1% level. |
本系統中英文摘要資訊取自各篇刊載內容。