平面钢管桁架平面外稳定混合有限元分析

Analysis of Out-of-plane Stability for Planar Tubular Truss with Mixed Finite Elements Method

平面外失稳通常是无支撑平面钢管桁架在极限荷载作用下的破坏形式之一。在平面钢管桁架平面外稳定问题的求解方法中,采用梁-板壳混合有限元模型在完成整体稳定分析的同时,还可以得到节点区域实际的受力状况,且具有求解精度较高、单元数量较少的特点。根据混合有限元的基本原理,给出了混合单元交界上的结点约束方程。针对混合有限元求解方程的特点,为避免在求解上遇到数值困难,给出了混合单元模型在单元划分、求解方法上的原则和建议。数值算例与试验结果表明,混合有限元模型计算耗时较少,能较为准确的分析平面钢管桁架平面外失稳过程,提出的求解方法及建议较好的避免了数值困难的产生。

Out-of plane instability is usually one of the failures braces under uhimate load. The mixed model of beam and sh solving precision and less elements, can undertake overall sta for planar tubular truss without out-of-plane ell elements, with the characteristics of high analysis as well as the joints mechanic property when solving the issue of out of-plane stability. Based on the principle of mixed finite element, nodes constraint equations at the interface between beam elements and shell elements were derived. And advices on the element division and solving method were proposed in order to avoid numerical difficulty in solving the mixed finite element equations. With the numerical solution and experimental test. it was found that the out-of plane instability process can be expressed accurately with less time consuming by the proposed method and the proposed solution.