木理倾斜角及含水率对木材压缩强度之影响.PDF

木理傾斜角及含水率對木材壓縮強度之影 響 卓志隆 國立宜蘭技術學院森林系教授 摘要 本研究之目的在探討木理傾斜角及含水率對四種國內經常使用之木結構用材(花旗松、美國側柏、阿 拉斯加扁柏及雲杉)壓縮強度的影響，無缺點試材取自斷面 2×4 英吋之乾燥商用製材品。試驗結果顯示木 o o 理傾斜角(0 -90 )對壓縮強度之影響相當顯著，其關係可以 Hankinson 公式表示，四個樹種的平均 n 值為 2.64 。並由統計下限值的觀念計算出不同角度時之壓縮強度比，依據此結果可更正確計算壓縮容許應力值。 在含水率 25%以下時，壓縮強度隨著含水率降低會顯著地增加，以 15%含水率時之壓縮強度（σ15 ）為基準 時，含水率每改變 1%時，縱向壓縮強度的平均變化率（α）為 6% 。但樹種間存在某些差異性，以花旗松 及雲杉的α值較大，美國側柏及阿拉斯加扁柏的值較小。 關鍵詞 ：壓縮強度、木理傾斜角、含水率、Hankinson 公式 Effects of Grain Angle and Moisture Content on the Compressive Strength of Wood Chih-Lung Cho Professor, Department of Forestry , National I-Lan Institute of Technology Abstract The purpose of this study was to investigate the effects of grain angle and moisture content on the compressive strength of four wood species(Douglas-fir, western red cedar, Alaska cypress and spruce),which were frequently utilized for building construction in Taiwan . Clear specimens were cut from commercially dried 2- by 4-inch saw lumber. Results indicated that the compressive strength of four wood species were significantly o o affected by their grain angle(ranged from 0 -90 ). Their relationship could be represented by Hankinsons formula, and the average value of n for this formula was 2.64. By the way, from the statistic concept of lower limit, the compressive strength ratios at various grain angle were calculated. In accordance with this result, the compressive allowable stress will be induced more accurately. Below 25% moisture content, the compressive strength increase significantly with decreasing moistur