本文以二維等寬度漸變矩形斷面且同時承受彎矩及軸壓力作用的簡支撐柱為對象，建立數值方法分析鋼構件的彈塑性行為。並計算構件發生最大應力的斷面，當構件斷面塑化時，修正勁度以反應出勁度衰減的趨勢。且預測塑性鉸於構件內部可能形成的位置，以獲得最合理的載重－位移曲線。本文製作三種結構模型，並進行載重與位移測試，藉以驗證理論分析的正確性。

　　　　　A planar tapered column of rectangular cross section with constant width is studied in this project. The elastic-plastic behavior of a tapered member is investigated by using a simply supported column subjected to external moments and axial force. When the cross-section in a member is partially plastic, the stiffness matrix is modified to represent the degradation of stiffness. The possible position of plastic hinge can be predicted. Hence, the most reasonable load-deflection response can be represented. Three types of structural model were made and tested. The load-deflection responses of members were detected. The validity of theoretical analysis is verified.