柳杉疏伐木製造之集成材抗彎性質評估

Evaluation on the Bending Properties of Glulam Made from Japanese Cedar Thinned Log

卓志隆(Chih-Lung Cho) ； 顏廷諭(Ting-Yu Yan) ； 洪崇彬(Chung-Pin Hung)

《林產工業》 29卷4期 (2010/12) Pp. 227-236

https://doi.org/10.6561/FPI.2010.29(4).2

摘要

本研究以羅東林區管理處所收穫之51年生柳杉（Cryptomeria japonica）疏伐原木作為結構用集成材製造之原料，原木製成尺寸規格集成元並經人工乾燥作業後，以超音波方法量測各集成元彈性模數（E_u），透過彈性模數等級區分後並依CNS11031標準規定，將集成元配置成五種預測彈性模數等級（E75、E85、E95、E105、E120）之小斷面與中斷面同等級和對稱異等級結構用集成材。研究結果顯示平均末端直徑250mm之原木製成集成元之利用率為42.3%。柳杉集成元依彈性模數（E_u）等級區分結果以L60至L110等級為主。小斷面集成材之預測彈性模數與抗彎彈性模數實測值間平均差異百分率為7.6%，中斷面集成材兩者間的平均差異百分率為14.9%。5種組合型式之小斷面同等級與對稱異等級集成材之抗彎彈性模數及抗彎強度之平均值與5%下限值符合CNS11031規定之要求；中斷面集成材則因抗彎彈性模數平均值或其5%下限值較規定數值低，無法達到預期設計等級之目標。

關鍵字

柳杉 ； 結構用集成材 ； 超音波方法 ； 彈性模數 ； 抗彎強度

並列摘要

Structural glulam (Glued laminated timber) made from 51-year-old Japanese cedar (Cryptomeria japonica) thinned logs harvested by Luodong forest management district office was investigated in the study. Laminae for manufacture of the structural glulam were obtained by sawing logs into green dimensional materials. After kiln-drying, the value of modulus of elasticity (E_u) for each lamina was determined by ultrasonic testing method. Five predicted E-rated types (E75, E85, E95, E105, and E120) for producing various combinations of uniform and balanced symmetrical glulam with small- and medium-dimension cross section were designed on the basis of laminae properties complying with CNS11031 procedures. The experimental results indicated the yield of laminae from logs with on average diameter of 25 mm was 42.3%. The major E-grades of Japanese cedar laminae according to E_u determination were among L60 to L110. The average percentage difference between the predicted design and actual static modulus of elasticity for various combinations of glulam with small-dimension cross section was 7.6%, and that of glulam with medium-dimension cross section was 14.9%. Both the mean and 5^(th) percentiles values of bending stiffness and strength for five E-rated combinations of uniform and balanced symmetrical glulam with small-dimension cross section met the requirements of CNS11031 standard. Because the mean or 5^(th) percentiles values of bending stiffness were lower than criteria values, glulam with medium-dimension cross section manufactured in this study could not achieve the target levels.

並列關鍵字

Japanese cedar ； Structural glued laminated timber (Glulam) ； Ultrasound method ； Modulus of elasticity ； Bending strength