35年生國產柳杉分等結構用材之機械性質評估

Mechanical Properties of 35-year-old Japanese Cedar Graded Structural Lumber in Taiwan

李佳如(Chia-Ju Lee) ； 張夆榕(Feng-Rong Chang) ； 林志憲(Chih-Hsien Lin) ； 楊德新(Te-Hsin Yang)

《林產工業》 33卷2期 (2014/06) Pp. 61-70

https://doi.org/10.6561/FPI.2014.33(2).1

摘要

本研究評估35年生國產柳杉分等結構用材之基本性質，並透過非破壞檢測技術評估其彈性模數，以及建立抗彎彈性模數分等級距，探討其柳杉分等材抗彎性質之特徵值與容許應力值，以做為未來柳杉製材結構設計之參考。結果指出，35年生之國產柳杉結構用材抗彎強度為53.06 MPa、抗彎彈性模數為7.12 GPa，經彈性模數分等後，主要集中在E70級（佔整體柳杉之40.7%），其次為E50級（佔整體柳杉之23.1%）與E90級（佔整體柳杉之20.9%）。藉由超音波法、應力波法與打音法評估柳杉結構用材之抗彎彈性模數顯示，其相關係數r值為0.64－0.74間，其中以打音法較為準確，未來可利用此法進行柳杉製材之評估與分級，此外，經彈性模數分級後之柳杉製材，其抗彎性質之特徵值與容許應力均隨彈性模數等級提升而增大，且相較於未分等之柳杉製材強度集中，因此經機械分等之柳杉造林木，可有效提升其利用效率，亦可作為未來柳杉製材應用於木質結構設計之參考。

關鍵字

柳杉 ； 機械性質 ； 容許應力

並列摘要

In this study, the fundamental properties of 35-year-old Japanese cedar (Cryptomeria japonica) wood were investigated. The bending properties of Japanese cedar lumber were evaluated by nondestructive testing (NDTs), in addition, the values of parametric tolerance limit and allowable stress of each E-grading group were also demonstrated. Results indicated that the modulus of rupture (MOR) and modulus of elasticity (MOE) of Japanese cedar lumber were 53.06 MPa and 7.12 GPa, respectively. It also showed that most lumber was mainly in E70 group (about 40.7% of all specimens), followed by E50 (about 23.1% of all specimens) and E90 group (about 20.9% of all specimens). The relationships among dynamic MOE, which were calculated by ultrasonic testing, stress wave testing, tap tone testing, and MOE of lumber were also found (r=0.64- 0.74). After E-grading, the values of parametric tolerance limit and allowable stress of each Japanese cedar lumber increased with E-grading increased. Moreover, lower variations of bending strength were found in E-grading groups than those without grading. Hence, the E-grading Japanese cedar lumbers can improve the efficiency of utilization and can apply the information for wood structure design.

並列關鍵字

Japanese cedar ； Mechanical properties ； Allowable stress