不同連接法對桂竹十字搭接接點力學行為之影響

Abstract

本研究使用臺灣桂竹（Phyllostachys makinoi）竹桿做為試驗材料，以十字搭接做為接合形式，並評估日本黑繩、鐵線及金屬托架做為竹材接點固定工法之影響，先利用橫向部分壓縮試驗對竹桿進行機械性質檢驗及篩選，並透過拉伸、滑移及旋轉三種機械性質試驗以建立竹材接點性質試驗方法及進行力學行為之分析。由橫向部分壓縮試驗結果指出增加竹節數目及取樣位置接近竹桿基部皆能增加竹桿部分壓縮之極限荷載，而單節及無節、中段及末端兩組試材具有相似之部分壓縮強度。拉伸試驗指出增加竹節數目對綁繩接點極限荷載之增強效果比增加迴圈數有效，而3迴圈即可使竹桿間有足夠之拉伸極限荷載（602.52 kgf）。三種接點之拉伸勁度由大至小依序為鐵線、綁繩及金屬托架，而極限荷載方面則反之。滑移試驗指出綁繩接點於3迴圈後滑移勁度即無明顯增強效應，而竹節之存在能夠有效增加綁繩接點及鐵線接點之極限荷載及滑移勁度，而金屬托架接點具有最佳之滑移勁度，滑移極限荷載由大至小依序為金屬托架接點、綁繩接點及鐵線接點。旋轉試驗中三種接點之旋轉勁度由大至小分別為金屬托架、綁繩及鐵線，於分類上三種接點之接合形式皆為不能移動但可自由轉動之鉸接點。

This study evaluated the mechanical properties and behaviors of bamboo joints connected by different connection type. Cross-lap joints of Phyllostachys makinoi culms were connected by using Japanese black rope, iron wire and steel angle brackets. Mechanical properties of the bamboo culms were examined using lateral partial compression test, and the mechanical behaviors of cross-lap bamboo joints were determined using tensile, slip and rotation tests. Results of lateral partial compression test indicated enhancement in ultimate partial compressive load with increase in number of bamboo nodes and with sampling position closer to the base of the bamboo culm. Similar performance in partial compressive strength was observed for specimens with no and single node as well as with sampling positions in middle and end of bamboo culms. Results of tensile test revealed higher ultimate load in lashing joints with larger number of bamboo nodes than in those with more loops. It was found that three loops could yield sufficient tensile load (602.52 kgf) between bamboo culms. Of the three fixing materials, iron wire gave the highest tensile stiffness to the joint, followed by rope and steel angle bracket. In contrast, steel angle bracket gave the highest ultimate load, followed by rope and iron wire. Performance in slip test showed no significant gain in slip stiffness for joints lashed with more than three loops. Moreover, the presence of bamboo nodes could effectively increase the ultimate load and slip stiffness of joints lashed with rope and iron wire. Comparing results between tensile and slip tests showed that joints fixed with different materials had directional stiffness and ultimate load. Joints fixed with steel angle bracket had the highest slip stiffness and rotational stiffness, followed by those lashed with rope and iron wire. Regardless of the fixing materials used, the studied cross-lap joints are all classified as hinged joints.