【摘要】 运用二阶理论建立的梁－柱平衡方程导出平面梁单元刚度矩阵；在小变形条件下，该刚度阵精确地包含了梁单元的线性刚度阵和几何刚度阵。由结构刚度矩阵行列式值为零的失稳条件导出结构失稳特征方程，从而精确地确定系统临界力值。本文以起重机箱形伸缩吊臂为例，对多节变截面阶梯柱的稳定性进行分析，给出任意阶起重机箱形伸缩臂临界力求解的精确递推公式。更多还原

【Abstract】 The beam element stiffness matrix on plane problem can be got from the equilibrium equation of a beam -column which is built according to the theory of Ⅱ order. On condition that the deformation of element is small, the stiffness matrix consists of linear stiffness matrix and geometrically nonlinear stiffness precisely. The precise critical force of a system can be deduced from the fact that the determinant of stiffness matrix of the system is equal to zero in the critical condition. As an example, the stability analysis of a multistepped column is discussed, and a precise recurrence formula is offered to solve the problems of critical force of any telescopic boom in crame.更多还原