运用精确有限元理论的单元刚度矩阵来分析桁架结构的稳定性问题，推导了桁架结构临界失稳的判别式.结合判别式从理论上阐述了结构发生失稳的2种不同类型，并解释了有限元软件分析超静定桁架结构稳定性出现误判的原因.通过对有限元方法求解稳定问题的实质和过程进行分析，提出了解决有限元软件误判的方法，运用单元撤换法处理局部失稳后的系统模型，更准确地评估结构稳定性承载能力.利用基于ANSYS软件二次开发程序,改进了应用有限元软件分析超静定结构稳定性的方法，以获取超静定杆系结构真实的临界失稳载荷.%In this study, the truss structural stability is analyzed using the elemental stiffness matrix of precise finite element theory. Meanwhile, the critical instability discriminant is deduced for truss structure. Through theoretical description upon two types of structural instabilities, the reasons for finite element misjudgment are explained in terms of hyper-static truss structural stability. By analyzing the stability solution and process via finite element methods, a method to solve finite element misjudgment is proposed. Particularly, the elemental replacement method, which can more accurately evaluate the loading capacity of structural stability,is used to deal with the local instability. Based on the secondary development via ANSYS? ,the analysis method for hyper-static structural stability is improved so as to obtain the critical instability loading for bar system structure.
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