應用振動法評估生物性劣化杉木之性質

Properties Evaluating of Biologically Degraded China Fir by Vibration Method

卓志隆(Chih-Lung Cho)

《林產工業》 19卷4期 (2000/12) Pp. 495-503

https://doi.org/10.6561/FPI.2000.19(4).11

摘要

杉木為台灣地區木結構古蹟建築中相當重要之構件材料。木材在使用過程中，經常遭受腐朽菌及白蟻危害造成可承受載重能力降低，因此要確定古蹟結構構件適當的現況殘留強度且作出合理之修補或更新決定，需要對木材狀況有正確評估。本研究以非破壞性振動方法評估杉木受到密褐摺菌（Gloeophyllum trabeum）及家白蟻（Coptotermesformosanus）危害後不同劣化程度之性質變化，並由非破壞量測參數推估劣化後之殘留強度。由振動方法量測之縱向速度，縱向及彎曲動彈性係數均能定量化評估杉木劣化程度，尤其是以縱向動彈性係數預測劣化程度之相關性最高。在相同重量損失率時，褐腐菌對於這三項性質造成危害的影響大於白蟻。縱向壓縮強度及靜曲強度則在腐朽初期時，已迅速降低，且在不同劣化程度時，因腐朽菌引起之強度減低明顯高於白蟻之危害。生物性劣化後之杉木殘留強度與非破壞量測參數間呈顯著指數關係，其中以縱向動彈性係數推估殘留強度之迴歸相關係數最高。但以縱向速度評估白蟻劣化後之殘留強度，則其可靠性較低。因此以縱向動彈性係數作為杉木構件現況殘留強度的推估指標會較準確。

關鍵字

生物性劣化 ； 褐腐菌 ； 白蟻 ； 杉木 ； 非破壞振動方法 ； 縱向速度 ； 縱向及彎曲動彈性係數 ； 殘留強度 ； 劣化等級

並列摘要

China fir are the very important structural members of historic timber construction buildings in Taiwan. Wood in service life usually attacked by decay fungi and termites, thereby reducing its ability to carry load. So, determining an appropriate load capacity for a historic structural member and making rational decisions about repair or replacement necessiate an accurate assessment of the wood condition. Nondestructive vibration method was used in this study to evaluate properties of China fir exposed to brown-rot fungi (Gloeophyllwn trabewn) and termites (Coptotermes formosanus) to various degree of attack. Residual strength of degraded wood was also estimated by nondestructive parameters. Results showed that measurement of longitudinal velocity, longitudinal and flexural dynamic modulus of elasticity by vibration method will yield quantitative information on the extent of biodegraded degree of China fir, especially longitudinal dynamic modulus of elasticity provided the highest correlation when used to predict degraded condition. The influence of brown-rot fungi attack on the three mentioned properties was greater than termites. At the same percent weight loss, Crushing strength parallel to grain and bending strength decreased rapidly at the incipient stage. Strength reduction caused by brown-rot fungi attack obviously higher than termites at various degraded degree. Nondestructive parameters provided significantly exponential correlation to estimate residual strength of biodegraded China fir, of these regression when used longitudinal velocity to evaluate residual strength of termite degraded wood. Longitudinal dynamic modulus of elasticity as the indicator for estimating in-place residual strength of biodegraded China-fir will provide higher accuracy.

並列關鍵字

Biodeterioration ； Brown-rot fungi ； Termite ； China fir ； Nondestructive vibration method ； Longitudinal velocity ； Longitudinal and flexural dynamic modulus of elasticity ； Residual strength ； Degraded level