关键词: 竖向立柱, 侧向约束, 动态施工, 初始缺陷, 稳定承载力, 计算长度

Abstract: The vertical column is a key step of the design of foundation pit using top-down method; and the lateral restraint under dynamic construction is the main factor to determine the stability of the vertical column. For the axial compression stability of the vertical column under top-down construction, the finite element method is used to obtain the buckling load; and then through Euler formula of rods, the calculation length coefficient of the vertical column is obtained by inverse derivation. The linear eigenvalue buckling analysis is applied to study the capacity and stability of the vertical column under the dynamic variation of the excavation by steps of foundation soil and the lateral restraint. Then the fitting formula of the calculation length coefficient is put forward in the analysis of the stability bearing capacity for the vertical column. Nonlinear buckling analysis takes into account the influence of the geometric large displacement; and then the equilibrium path of post buckling is obtained by applying the initial geometric imperfection. It is shown that the actual bearing capacity of the vertical column with initial imperfection is smaller than that of the eigenvalue buckling load; and the lager the initial imperfection amplitude, the smaller the stable bearing capacity of the vertical column.

Key words: vertical column, lateral restraint, dynamic construction, initial imperfection, stable bearing capacity, calculated length