頁籤選單縮合
題 名 | 栽植距離對柳杉強度變異性影響之研究(1)--靜力機械性質=Effects of Planting Distance on the Strength Variation of Japanese Cedar (Ⅰ)--Static Mechanical Properties |
---|---|
作 者 | 卓志隆; | 書刊名 | 林產工業 |
卷 期 | 17:3 1998.09[民87.09] |
頁 次 | 頁453-469 |
分類號 | 436.18 |
關鍵詞 | 柳杉; 栽植距離; 機械性質; 密度; 5%排外水準值; 容許應力; Japanese cedar; Plantation spacing; Mechanical properties; Density; Lower 5% exclusion limit; Allowable stress; |
語 文 | 中文(Chinese) |
中文摘要 | 本研究之柳杉試材取自本省溪頭戶驗林區40年生之立木,採用中國國家標準之木 材靜曲強度、壓縮強度、引張強度及剪斷強度試驗法測試五種不同栽植距離之無缺點小試材 , 在生材及氣乾狀態下 (含水率約為 15 % ) 之各項強度性質,由強度之變異性分佈計算 在 95 %信賴區間內 5 %之排外水準值作為基準應力, 由此應力推估柳杉各品等之容許應 力值。 本研究得到如下結果: 1. 栽植距離 1mx1m 之柳杉林木, 其平均絕乾密度最大為 426kg/m �纂A栽植距離 5mX5m 最低,密度與各項機械性質皆呈極顯著正相關關係。2. 栽植 距離 1ImX1m 之柳杉林木,其平均年輪寬最窄,為 5.23mm。 而平均年齡寬與絕乾密度間呈 負相關。 3. 柳杉機械性質不論是氣乾或生材狀態以引張強度 > 靜曲強度 > 縱向壓縮強度 > 剪斷強度。4. 靜曲及縱向壓縮強度,不論是氣乾或生材狀態皆以 1mx1m 栽植距離者最大 ,5mX5m 最小,而 2mx2m,3mx3m,4mx4m 間,則不具有顯著差異。5. 含水率對於柳杉壓縮 強度的影響最大,對於引張強度的影響最小。 6. 溪頭地區各品等柳杉木材,依生材狀態之 5 % 排外水準值所推估容許應力值如表 14 所列,以靜曲強度最大,剪斷強度最小。7 .若以柳杉平均機械性質或密度考量材質, 則柳杉林木採用 1mX1m 栽植距離下生長至樹冠 鬱閉後,再進行適當的疏伐作業,對林木材質有正面效果。若以容許應力值考量,則各栽植 距離間差異不大。 |
英文摘要 | The Japanese cedar (Cryptomeria japonica D.Don) specimens of this study were manufactured using the planted trees sampled from forty year old trees at Chi-Tou experimental forest in Taiwan.The mechanical properties of small,clear specimens from five plantation spacing samples were obtained by CNS static bending, compression parallel to grain, tension parallel to grain, and shear strength methods.The moisture content of tested specimens were green and air dry(15%) respectively. From the variance of respective strength, the lower 5% exclusion limit (EL 5 %)of distributed population can be calculated with 95% confidence. We can estimate allowable properties of different grade lumber by EL 5% and adjustment factor. The following conclusions can be drawn from this study: 1.The oven dry density of the 1m x 1m plantataion spacing was the largest (426kg/m3),and the 5m x 5m was lower. The two-type plantation spacings (1m x 1m, 5m x 5m) on oven dry density both show their significant difference, at 95% probability level,in comparison with the other three-type plantation spacings (2m x 2m, 3m X 3m,4m X 4m ).There were significant positive relationships between density and various mechanical strength of Japanese cedar.2.The average annual ring width of 1m x 1m (5.23mm)was significantly lower than the other types. There was a negative relationship between oven dry density and average annual ring width.3.The mechanical properties of Japanese cedar, regardless of green or air dry condition, were proved squentially ordered as the followings: tensile strength> bending strength > crushing strength parallel to grain >shear strength.4.Both at green or air dry condition, the crushing strength,bending strength and modulus of elasticity of the 1m x 1m was significantly higher than the other four plantation spacings.The mechanical strength of 5m x 5m was lower. There were no significant difference among 2m x 2m, 3m x 3m and 4m x 4m plantation spacings.5.Among the various strength of Japanese cedar, the crushing strength depends greatly on moisture content, and the tensile strength was least affected by moisture content. 6.The allowable stress design values of different grade lumber of Chi-Tou area are given in Table 14. The bending strength is the highest, and shear strength is lower.7.From the viewpoint of mechanical properties or density, it is recommended to use plantation spacing 1mX1m, and to thin properly after the crown is crowded. This can produce the better quality trees. But if we consider the lower 5% exclusion limit, it shows no significant difference between various plantation spacing. |
本系統中英文摘要資訊取自各篇刊載內容。