含水率與密度對柳杉縱向抗壓強度之影響

Effects of Moisture Content and Density on the Compression Strength Parallel to Grain Direction of Japanese Cedar Wood

陳勁豪(Jin-Hau Chen) ； 薛惠今(Huei-Chin Shiue) ； 郭佩鈺(Pei-Yu Kuo) ； 王松永(Song-Yung Wang) ； 林法勤(Far-Ching Lin)

《中華林學季刊》 39卷3期 (2006/09) Pp. 367-376

https://doi.org/10.30064/QJCF.200609.0007

摘要

本研究將柳杉材由高含水率逐步乾燥至絕乾，在每一階段進行縱向抗壓試驗。結果發現當含水率在低於纖維飽和點時，縱向抗壓強度與含水率間呈現負線性相關。在低於纖維飽和點時，平均縱向抗壓強度變化率為4.3%；若以12%含水率為基準，含水率每增減1%時，平均縱向抗壓強度會減增3.6%；若以絕乾含水率為基準的抗壓強度時，當含水率增減1%時，平均縱向抗壓強度會減增2.52%。當含水率高於纖維飽和點時，縱向抗壓強度與含水率沒有明顯的相關性。若將12%含水率時木材的密度區分成＜0.4g/立方公分；0.4~0.45g/立方公分；以及＞0.45g/立方公分三群時，三群之間的生材含水率與抗壓強度皆有顯著性差異，當12%含水率時，其密度＜0.4g/立方公分群，含水率每增減1%，以12%為基準的抗壓強度會減增3.4%；當12%含水率時其密度為0.4~0.45g/立方公分群，含水率每增減1%，抗壓強度減增3.7%；當12%含水率時其密度為＞0.45g/立方公分群，含水率每增減1%，抗壓強度減增3.5%；若以絕乾含水率為基準的抗壓強度時，當含水率增減1%時，平均縱向抗壓強度，三群分別會減增2.42%、2.58%以及2.48%。若去除密度因子，以比強度與含水率來看，當含水率低於纖維飽和點時，含水率上升時，比強度呈下降的趨勢，其下降比例為每增減1%含水率時比強度會減增4.5%；若以絕乾含水率為基準的抗壓強度時，當含水率增減1%時，平均縱向抗壓強度會減增2.92%。當含水率高於纖維飽和點時，含水率上升時，比強度亦呈下降的趨勢但下降比例較為和緩。以破壞型態則以壓碎型抗壓破壞出現的頻率為最高，當碎裂型抗壓破壞出現時，其抗壓強度較大；而剪斷型抗壓破壞出現時，其抗壓強度較小。

關鍵字

縱向抗壓強度 ； 纖維飽和點 ； 柳杉 ； 含水率 ； 比強度

並列摘要

In different moisture content from high to oven dry, this research estimated the compression strength parallel to grain direction of Japanese-cedar. Below FSP, the compression in longitudinal direction to grain was with negative linear relationship with moisture content. Increasing 1% moisture content, the average compression in longitudinal direction to grain decreased 4.3% below FSP. If the standard was 12% moisture content, increasing 1% moisture content, the compression strength parallel to grain direction decreased 3.6%. If the standard was oven dry, increasing 1% moisture content, the compression strength parallel to grain direction decreased 2.52%. Above FSP, the compression strength parallel to grain direction didn't have apparently relationship with moisture content. Dividing density of 12% moisture content into three groups, the group included that density below 0.4g/cm^3, between 0.4 and 0.45g/cm^3, and above 0.45g/cm^3. There were obvious difference in moisture content and compression of the three groups. If the standard was 12% moisture content, increasing 1% moisture content, the compression strength parallel to grain direction of the density below 0.4g/cm^3 decreased 3.4%, the compression strength parallel to grain direction of the density between 0.4 and 0.45g/cm^3 decreased 3.7% and the compression strength parallel to grain direction of the density above 0.45g/cm^3 decreased 3.5%. If the standard was oven dry, increasing 1% moisture content, the compression strength parallel to grain direction of the density below 0.4g/cm^3 decreased 2.42%, the compression strength parallel to grain direction of the density between 0.4 and 0.45g/cm^3 decreased 2.58% and the compression strength parallel to grain direction of the density above 0.45g/cm^3 decreased 2.48%. Excluding the density factor, increasing 1% moisture content decreased 4.5% specific strength at the 12% moisture content and increasing 1% moisture content decreased 2.92% specific strength at the oven dry. As same as the compression strength, increasing moisture content the specific strength decreased but the decreasing range was smoother than compression strength below FSP. The crushing type was the most common type of all. The crushing type had the higher compression strength and the shearing type had the lower compression strength.

並列關鍵字

Compression strength parallel to grain direction ； Fiber saturation point ； Japanese-cedar ； Moisture content ； Specific strength