本文旨在探討配置不同縱向鋼筋量之鋼筋混凝土梁，受到彎矩和扭矩之組合載重作用下之承力行為。經由試驗方法來比較鋼筋混凝土梁在組合載重下之強度與勁度的差異、試體表面裂縫的發展、混凝土軟化以及頂面內部應變的變化。
本研究共規劃13根斷面尺寸為420×420mm之鋼筋混凝土方形斷面試體，其中包括高強度混凝土(fc’＝69 MPa) 11根以及普通強度混凝土(fc’＝35 MPa) 2根。主要考慮變數為縱向鋼筋量(Al)、扭矩和彎矩組合載重比例值(T/M)及混凝土抗壓強度(fc’)等。
研究結果顯示：（1）試體之實測開裂強度與Collins的預測式所得到之開裂強度的比值介於0.7～0.9之間。對於配置較高縱向鋼筋量之C系列試體，在承受彎矩和扭矩之組合載重作用時，試體之實測極限強度值為理論預測式所得到之極限強度值的1.2倍；（2）當試體內部的鋼筋量相同之情況下，試體受組合載重作用之扭矩比重越小時，開裂初期的扭轉勁度與撓曲勁度均會增加；（3）試體頂面混凝土之主張應變會隨著T/M比例值的增加而增大，進而造成頂面混凝土之極限主壓應變值因軟化現象而降低；（4）在達極限階段時，試體頂面的壓力區厚度會隨著T/M比值下降而減小。當試體所承受彎矩和扭矩之組合載重的比例值(T/M)為Tu0/Mu0時，達極限強度時頂面壓力區厚度會隨試體配置之縱向鋼筋量的增加而增大。

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