(同济大学建筑工程系 上海 200092)
【提要】 上海南站是国内外第一座大型圆形火车站建筑，该建筑屋盖为预应力索梁结构体系，大跨度钢梁特殊的平面呈Y形，截面为橄榄形薄壁闭口截面，使结构设计有较大难度。介绍了结构局部模型边界条件的确定方法，运用大型有限元分析软件MSC.MARC详细分析了该梁的极限承载力，为该结构设计提供了可靠的计算依据，为此类结构的分析提供有价值的参考资料。计算结果表明，只有综合考虑结构的几何和材料非线性才能准确评估出结构的极限承载力。
【关键词】 橄榄形薄壁闭口截面 弹性边界条件 几何非线性 材料非线性 极限承载力 Y形梁 钢梁
Ultimate Bearing Capacity Analysis of Yshape Girder of Roof Steel Structure of Shanghai South Railway Station/Su Ci, Luo Yongfeng, Shen Zuyan, Guo Xiaonong (Department of Building Eng., Tongji Univ., Shanghai 200092, China)
Abstract:Shanghai south railway station is the first large round building of which roof is a system of prestressed cables and beams. The steel girders of the roof structure are closed ellipse sections, which bring out difficulties for design. The methods to specify boundary conditions applying to local model are discussed. The ultimate bearing  capacity of the girder is analyzed by using MSC.MARC，which provides reliable basis for the structure design.The analysis procedure  can be reference for similar structure design. The results indicate that the ultimate bearing capacity of structure can be evaluated exactly when considering both geometric nonlinear and material nonlinear.
Keywords:ellipse closesection shape; elastic boundary condition; geometric nonlinear; material nonlinear; ultimate bearing capacity; Ysteel girder;