長細比對巒大杉圓柱與梭柱縱向抗壓強度之影響

Effect of Slenderness Ratio on the Compressive Strength Parallel to Grain of Round and Shuttle-shaped Columns Made of Luanta Fir

卓志隆(Chih-Lung Cho) ； 黃仰禾(Yang-He Huang)

《林產工業》 30卷1期 (2011/03) Pp. 13-22

https://doi.org/10.6561/FPI.2011.30(1).2

摘要

本研究透過抗壓強度試驗與彎曲自由振動試驗，探討不同長細比下巒大杉圓柱與梭柱試材的縱向抗壓強度性質，並依試驗分析結果評估其臨界抗壓應力與長細比容許值。研究結果顯示圓柱與梭柱之縱向抗壓強度與縱向抗壓比例限度應力皆隨著長細比增加呈降低之趨勢。在相同長細比條件下，中短柱形式之圓柱與梭柱間之縱向抗壓強度差異很小，但長柱形式的梭柱試材則較圓柱縱向抗壓強度高12.42%。圓柱與梭柱之縱向抗壓比例限度應力與縱向抗壓強度平均比分別為0.726及0.804。依據Euler公式及FPL公式預測之梭柱臨界抗壓應力平均較圓柱高2.28%，顯示梭柱形式的設計除了美觀外，亦有力學設計的目的。在較保守的結構設計下，建議巒大杉作為柱構件使用時，其長細比容許值為80。

關鍵字

巒大杉 ； 長細比 ； 梭柱 ； 縱向抗壓強度 ； 臨界抗壓應力

並列摘要

Compressive tests and flexural free vibration tests were conducted on Luanta fir (Cunninghamia konishii) specimens of round column and shuttled-shaped column for a range of slenderness ratio to investigate their compressive properties parallel to grain. The critical compressive stress (fcr) and a value of allowable slenderness ratio of wooden column were evaluated by comparison with experimental analysis. The results indicated that both compressive strength parallel to grain (σc) and compressive stress at proportional limit (σcp) decreased with increasing slenderness ratio. The percentage differences of σc with respect to round column and shuttle-shaped column specimens in the short and intermediate column range were very small at the same slenderness ratio. But the value of σc for shuttle-shaped column specimens in the long column range was 12.42% higher than that of round column specimens. The values of σcp/σc for round column and shuttle-shaped column specimens were 0.726 and 0.804 on average, respectively. The values of fcr predicted by Euler's and FPL equation for shuttle-shaped column were 2.28% on average higher than those of round column. This result reveals shuttle-shaped column used in Chinese traditional building not only for aesthetics, but also for the mechanical design purpose. Regarding the conservative design of Luanta fir used in wooden construction, the allowable slenderness ratio at a value of 80 was suggested for the column member.

並列關鍵字

Luanta fir ； Slenderness ratio ； Shuttle-shaped column ； Compressive strength parallel to grain ； Critical compressive stress.