薄壁构件整体稳定性的有限元模拟

Finite element modelling of thin-walled members in overall stability analysis

对薄壁构件整体稳定性分析中的薄壁梁单元和壳体单元两种有限元模型的特点进行了讨论,并提出一种新的适用于薄壁构件整体稳定分析的壳体单元模型,该模型可以有效消除各种局部屈曲模态的影响.采用通用有限元软件ANSYS,分别利用壳体单元模型和薄壁梁单元模型,分析了双轴对称截面梁、单轴对称截面梁、轴心受压构件、压弯构件和变截面梁的稳定性,通过与经典解或已有研究结果的比较对有限元模型的可靠性以及存在的问题进行了讨论.通过分析,发现ANSYS的薄壁梁单元模型不能用于分析单轴对称截面梁和压弯构件的弯扭屈曲,同时在分析变截面薄壁构件的稳定性时可能产生较大的误差;常用壳体单元模型可能由于截面的局部屈曲模态不能得到整体屈曲的临界荷载;提出的壳体单元模型可以精确模拟薄壁构件的整体稳定性.此外,提出的壳体单元模型不仅可以用于分析薄壁构件的整体稳定性,也可以作为检验薄壁构件整体稳定理论正确性的重要依据.

In the overall stability analysis of thin-walled members employing the general purpose finite element（FE） softwares,the members are generally modelled using the thin-walled beam elements or the thin shell elements.The modelling details of these two FE models were presented,and a new thin shell element model,capable of prohibiting the local buckling modes in the overall buckling analysis,was proposed.The two types of FE models were then adopted into the buckling analysis of thin-walled members,including the beams and columns with doubly and singly symmetric sections,beam-columns,tapered beams.The comparisons of the results from FE analyses,analytical solutions and literature show that the proposed thin shell element model is superior to the existing models of this type;the thin-walled beam element of ANSYS is not applicable to the flexural-torsional buckling analysis of thin-walled beams and beam-columns of mono-symmetric section,and significant error may arise in buckling analysis of tapered beams using this element.The results from the presented shell element model can also be used as the benchmark results in verifying the buckling theory of thin-walled members.The outcome of this study may be helpful for modelling thin-walled members in overall stability analysis using general FE packages,not limited to ANSYS.