摘 要
本研究旨在探討鋼筋混凝土梁在承受扭矩與剪力之組合載重下，試體之裂縫型式、極限扭矩強度、扭轉勁度、表面應變與承力機構的變化，並藉由試體內、外部應變的變化驗證試體承力機構的改變。
本研究共規劃四根實心斷面與五根空心斷面之鋼筋混凝土試體（ MPa），斷面尺寸為350×500 mm。主要考慮變數為扭矩-剪力比值（T/V）、空心斷面與實心斷面。
試驗結果顯示：（1）當試體所承受之T/V比例值減小時，承力機構會由TYPE Ⅰ之空間桁架模式，逐漸轉變成TYPE Ⅱ之斜彎矩模式與TYPE Ⅲ之平面桁架模式；（2）TYPE Ⅰ試體在達極限強度時，承受T+V組合力作用面之表面平均主張應變與表面平均主壓應變，皆相當接近由軟化桁架模式所計算出來的理論值，並不會因為試體承受的T/V比例值改變或是實心與空心斷面的效應而有明顯的差異；（3）配置低鋼筋量的實心斷面試體在承受高T/V比例作用下，由於側向曲率的作用，導致壓力區深度增加，使得極限扭矩強度會略微提升，而配置低鋼筋量的空心斷面試體在承受高T/V比例作用下，由於壁厚的限制無法進一步提供更多的混凝土來抵抗外力，所以極限扭矩強度無法向上提升；（4）當試體承受之T/V比例減小，翹曲效應亦隨之減小，且試體於T+V作用面的壓力區深度會逐漸變大；（5）TYPE Ⅰ試體的承力機構係以薄壁管類比承受扭矩與剪力之組合載重，其壓力區深度由大到小依序為T+V、T與T-V作用面，而TYPE Ⅱ試體之破壞模式屬於斜彎矩型，故不適用薄壁管理論來探討其承力行為。

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