世博轴索膜结构方案演变与结构参数分析

上海世博轴索膜结构的设计经历了多种方案的比选。以世博轴特大型张拉索膜结构的设计过程为主线，采用非线性有限元方法对该项目各种方案的结构响应进行计算。结构选型提出了无谷索方案、有谷索方案、重锤方案以及内桅杆方案，对比分析了四种方案结构的受力和变形特征，研究了世博轴索膜结构的受力性能变化与方案演变过程，确定结构最终方案为内桅杆体系。并依据自重、弹性模量、泊松比以及支承等因素对结构性能的影响进行了参数分析，分析结果表明：结构体系是影响系统力学性能的主要因素，弹性模量、泊松比等材料属性对结构的整体性能的影响很小；当膜面跨度较大或使用较重的膜材时，建议在找形阶段应考虑自重的影响；为避免计算假定与实际情况脱节，对于柔性支撑体系建议采用整体模型进行分析。图14表7参3

Evolution and parameter analysis of cable-membrane structure for the Expo Axis

Taking the design process of the Expo Axis cable-membrane structure as a subject, this paper discussed the mechanical evolution and scheme development. Various schemes were proposed along with the analysis of structural response using nonlinear finite element method. The comparison of stress and deformation analysis were made in the study from several angles such as without valley cable scheme, with valley cable scheme, gravity hammer scheme, and middle mast scheme. Parametric analysis was carried out including analyzing the relationship between structural performance and dead weight, elastic modulus, Poisson's ratio, flexible boundary, etc. The results show that structural alternative is the major factor that affects mechanical properties of the system, while material properties have the minimal impact on the overall performance. The structural weight should be taken into account at form-finding stage for long-span structure or heavier membrane. It is recommended that the flexible support system should be adopted to avoid the inconsistence of the calculation assumptions and the actual situation.