凯威特单层球面网壳的几何缺陷相关性

Correlation of the Geometric Imperfection of Kiewit Single-Layer Latticed Spherical Shell

凯威特单层球面网壳结构的稳定性对初始几何缺陷非常敏感,特别是节点位置安装误差造成的结构曲面形状偏差.由于单层网壳结构各节点之间由刚性杆件连接,因而不同节点的位置偏差具有相关性.理论分析和实测数据均表明,单层球面网壳结构中节点距离越远,节点位置偏差的相关性越弱.根据对节点位置偏差相关系数的计算推导和分析,建立以节点空间距离为自变量的相关系数函数,提出初始几何缺陷相关性的分式函数计算模型,并给出具有相关性的初始几何缺陷生成方法.建立凯威特单层球面网壳结构数值模型,根据提出的分式函数模型生成具有相关性的初始几何缺陷,将缺陷引入模型并进行整体稳定性分析,结果表明缺陷相关性会对结构整体稳定承载力产生明显影响.进一步对缺陷相关性进行参数分析,将不同相关程度和不同规模大小的缺陷引入模型中并计算结构整体稳定性,结果表明:初始几何缺陷较小时,相关性总是有利于结构稳定性;而缺陷较大时,结构稳定承载力会随相关性增强先减小后增大,中等程度相关性会对结构稳定性产生不利影响.因此,忽略缺陷相关性可能会使凯威特单层球面网壳结构稳定承载力的计算结果偏于危险,取相关系数为0.5进行分析,能有效考虑不利的相关缺陷.

The global stability of Kiewit single-layer latticed spherical shells is sensitive to initial geometric imperfection,particularly the imperfection of surface shapes caused by the positional deviations of structural nodes.Given that the nodes in a latticed spherical shell are connected by rigid rods,their positional deviations are correlated.From the theoretical analysis and practical data,the correlation coefficient of the positional deviations of the nodes decreases with the increase in nodal distance in the structure.To compute the correlation coefficient,a fractional function model that uses nodal distance as the independent variable was proposed.The steps used to derive the correlated positional deviations of the nodes were also given.On the basis of the fractional function model,a case study of a Kiewit single-layer latticed spherical shell was performed,which indicated that the correlation significantly influences the structural stability.The influence was assessed by further parametric analysis of the degree of correlation and the magnitude of geometric imperfection.Results showed that,when the magnitude of geometric imperfection is small,any degree of correlation enhances the structural stability.By contrast,when the magnitude of geometric imperfection is large,the structural collapse load initially decreases and subsequently increases with the increase in the degree of correlation.In other words,a medium degree of correlation reduces the structural stability.In conclusion,overlooking the degree of correlation might lead to an incorrect assessment of structural stability.And,a medium degree of correlation with the correlation coefficient equal to 0.5 was proposed.