多孔钢梁在组合屈曲模态下的非线性分析

讨论了一般强度和高强度多孔钢梁在组合屈曲模态下的非线性分析。建立一个考虑腹板和翼缘初始几何缺陷、残余应力和材料非线性等情况的多孔钢梁的三维有限元模型。用具有不同长度,不同截面,不同荷载条件和不同失效模态的多孔梁的试验结果验证了此有限元模型。该模型能计算多孔梁的失效荷载,跨中荷载-挠度关系和失效模态。用120根多孔梁的有限元计算数据进行了参数分析,研究截面几何尺寸,梁长和钢材料强度对多孔梁强度和屈曲性能的影响。参数研究结果显示:由于组合腹板的扭转和腹板后屈曲引起的多孔梁失效对承载力有很大的影响。对于长细比较小的多孔梁,应用高强度钢材料将能显著提高失效荷载值。将有限元计算得到的失效荷载与利用澳洲规范计算的多孔梁平面外屈曲计算结果进行了对比,发现规范的计算结果对于平面外屈曲的一般强度多孔梁是不保守的,而对于组合腹板扭转和腹板后屈曲的高强度多孔梁的失效则非常保守。

NonlinearAanalysis of Cellular Steel Beams Under Combined Buckling Modes

This paper discusses the nonlinear analysis of normal and high strength cellular steel beams under combined buckling modes.A nonlinear 3-D finite element model has been developed,which accounted for the initial geometric imperfection,residual stresses and material nonlinearities of flange and web portions of cellular steel beams.The nonlinear finite element model was verified against tests on cellular steel beams having different lengths,different cross-sections,different loading conditions and different failure modes.Failure loads,load-mid-span deflection relationships and failure modes of cellular steel beams were predicted from the finite element analysis.An extensive parametric study involving one hundred and twenty cellular steel beams was performed using the verified finite element model to study the effects of the change in cross-section geometries,beam length and steel strength on the strength and buckling behaviour of cellular steel beams.The results of the parametric study has shown that cellular steel beams failing due to combined web distortional and web-post buckling modes exhibited a considerable decrease in the failure loads.It is also shown that the use of high strength steel offers a considerable increase in the failure loads of less slender cellular steel beams.The failure loads predicted from the finite element model were compared with that predicted from Australian Standards for steel beams under lateral torsional buckling.It is shown that the Specification predictions are generally conservative for normal strength cellular steel beams failing by lateral torsional buckling,unconservative for cellular steel beams failing by combined web distortional and web-post buckling and quite conservative for high strength cellular steel beams failing by lateral torsional buckling.