Abstract: The balance differential equations of bending and torsion of the thin-walled component were derived from notional load technique method，on the base of the deformed structure and the equilibrium of a single plate． On the other hand，a large number of different bucklings with open thin-walled steel box with variable cross-section are analyzed by using finite element program ANSYS．It is concluded that，by vertical uniform loads，the cantilever thin-walled steel box which has open and variable cross-section has three basic forms of buckling，that is，the local buckling of plate，distortion buckling of cross-section and overall buckling of the component． With the change of structural size，first-order buckling form also changes in certain rules．

Key words: thin-walled steel box, notional load technique method, stability, buckling

摘要： 从薄板基本理论出发，利用单块板的平衡状态，将基本方程建立在变形后的结构上，用假想荷载法推导出了薄壁构件弯扭平衡微分方程; 以变截面开口薄壁钢箱为研究对象，用有限元软件ANSYS 对大量不同尺寸的结构进行了屈曲分析。研究发现: 受竖向均布荷载作用下变截面悬臂开口薄壁钢箱有3 种基本屈曲形态，即板件的局部屈曲、截面的畸变屈曲和构件的整体屈曲; 随着结构尺寸的变化，一阶屈曲形式也在发生变化，并且呈一定的规律。

关键词: 薄壁钢箱, 假想荷载法, 稳定性, 屈曲