評估臺灣櫸木作為柳杉建築木料之補強材料性質

Evaluating Properties of Zelkova serrata as Structural Reinforcing Materials for Construction Timber of Cryptomeria japonica

李佳如(Chia-Ju Lee) ； 蔡明哲(Ming-Jer Tsai) ； 莊閔傑(Min-Jay Chung)

《國立臺灣大學生物資源暨農學院實驗林研究報告》 33卷3期 (2019/09) Pp. 171-182

https://doi.org/10.6542/EFNTU.201909_33(3).0003

摘要

本研究利用臺灣櫸（Zelkova serrata）作為柳杉（Cryptomeria japonica）結構材的補強材料，並依據其強度性質、膠合性質、木螺釘保持力及尺寸安定性等分析來評估結構補強的可行性。試驗結果顯示臺灣櫸於柳杉上下二面的厚度各為5 mm補強試材之抗彎彈性模數及抗彎強度值分別為10.58 GPa及75.17 MPa，分別較柳杉材料提升141.6%及35.1%，顯示有良好的補強效果；當臺灣櫸補強厚度提升至7 mm時，其增加率與臺灣櫸所佔的體積比例呈正相關，且對於抗彎彈性模數的改善效應明顯地較抗彎強度值大。由臺灣櫸於柳杉二面補強厚度分別為3、5及7 mm之木螺釘保持力分別為850.24、957.13及1062.06 N，分別較未經補強之柳杉材料提升20.24、35.37及50.21%，顯示木螺釘保持力值與臺灣櫸補強厚度呈正相關，且經多變異數分析與Tukey同質性檢定後顯示三者之間具顯著性差異（p ＜0.05）。經浸水剝離試驗顯示五種補強組合型式之柳杉及臺灣櫸試材間的剝離率僅為0.1～0.5 %。再者，由柳杉及臺灣櫸試材間的膠合剪斷強度及木破率值分別為11.97 MPa及64.29%，顯示具有良好的膠合品質。於尺寸收縮率試驗結果顯示臺灣櫸做為柳杉之補強材料時，可明顯地降低尺度收縮率，故可提升尺寸安定性。

關鍵字

疏伐木 ； 臺灣櫸 ； 柳杉 ； 補強

並列摘要

This study evaluated the feasibility of plantation wood, Zelkova serrata, as structuralreinforcing materials for beams made with Cryptomeria japonica. We analyzed properties of strength, gluing, screw holding strength (SHS) and dimensional stability of C. japonica beams reinforced with Z. serrata on different sides and of various thicknesses. Results showed that the modulus of elasticity (MOE) and modulus of rupture (MOR) of beams with 5-mm Z. serrata glued to both upper and lower sides were 10.58 GPa and 75.17 MPa, respectively; which were 141.6% and 35.1% higher than those of non-reinforced control beams, indicating outstanding reinforcement effect. Further increase in thickness of Z. serrata to 7 mm led to strength enhancement proportional to volume ratio of Z. serrata,with greater improvement effect on MOE than on MOR. Similarly, reinforcement with Z. serrata increased SHS; and the thicker the Z. serrata added, the greater the enhancement in SHS compared with beams made with C. japonica alone (SHS of 850.24, 957.13 and 1062.06 N for 3-mm, 5-mm and 7-mm Z. serrata added, showing significant improvement of 20.24%, 35.37% and 50.21%, respectively). Results of peel test after water immersion showed only 0.1 ~ 0.5% peeling rates. In addition, the gluing shear strength and wood breaking rate between C. japonica and Z. serrata were 11.97 MPa and 64.29%, respectively, indicating good gluing quality between C. japonica and Z. serrata. Reinforcement with Z. serrata also reduced dimensional shrinkage rate of C. japonica, implying improvement in dimensional stability.

並列關鍵字

Thinned wood ； Zelkova serrata ； Cryptomeria japonica ； Reinforcing materials