在以古典塑性理論為基礎之混凝土模型中，加載函數在混凝土力學行為之預測上扮演著重要的角色。為求方便與一致，幾乎所有建立在塑性力學上之混凝土模型皆包含一個重要假設，即加載函數與破壞準則具有相同之形式。 在本研究中，發展出一個程式以應用塑性破壞模型於有限元素分析之中，對幾個常見的混凝土破壞準則進行比較，並假設加載函數與破壞準則無關以評估不同的降伏準則與加載函數在混凝土行為之預測上所造成的影響。此外，程式中並結合碎裂演算法以模擬混凝土之開裂行為。 研究結果顯示加載函數之選擇對混凝土力學行為之預測影響很大，加載函數與破壞準則具有相同形式之假設在某些加載狀態下可能導致較差的預測結果，將二者分開考慮可得到較精確之混凝土應力應變關係。 In the concrete models based on the classical plasticity theory, the loading function play an important role in the prediction of the behavior of concrete. For convenience and consistency, an important assumption in these models is that the yield criterion and subsequent loading functions have the same functional form as the failure criterion. In this study, a code was developed to implement the plastic-fracture model for finite element analysis. Several commonly adopted failure criteria are compared, and the effect of loading fuctions on the behavior of concrete are evaluated by the code. Besides, a fragmentation algorithm is incorporated into the code to simulate the cracking behavior of concrete. The results indicate that the prediction of the behavior of concrete is greatly affected by the choice of loading functions, and the models based on the assumption that the loading function and failure criterion have the same form may yield poor results under some loading conditions. Considering them separately may obtain the better prediction of stress-strain relationships of concrete.