初始几何缺陷模式对单层球面网壳抗震性能的影响

为探索地震作用下单层网壳的最不利初始几何缺陷分布模式,对施加四种初始几何缺陷的单层球面网壳分别开展了抗震性能研究。参照相关文献选取一致缺陷模态一、一致缺陷模态二,特征值缺陷及一阶振型缺陷四种典型的初始几何缺陷分布模式,并介绍了四种初始几何缺陷模式的理论计算公式及施加于理想网壳的方法;通过有限元建模分析,考察了施加四种初始几何缺陷模式后单层网壳的变形及自振频率变化;分别对跨度为100 m和其它不同参数的单层球面网壳施加上述四种初始几何缺陷模式、并分别输入七条选取于唐山地震主震实测三向地震动记录开展动力时程分析,考察四种初始几何缺陷模式对单层网壳动力工作性能及承载能力的影响。结果显示,对于矢跨比为1/3的单层球面网壳,施加一致缺陷模态一后网壳的最大节点位移值较大;其它参数的单层球面网壳,施加了特征值初始几何缺陷模式后网壳的最大节点位移值较大。该研究可对单层网壳开展动力工作性能分析及结构设计考虑地震作用时最不利初始几何缺陷模式的选取提供参考。

Effect of initial geometric imperfection modes on aseismic performance of single-layer spherical reticulated shell

In order to explore the most unfavorable initial geometric imperfection distribution modesof a single-layer reticulated shell under earthquake,aseismic performances of single-layer spherical reticulated shells with four initial geometric imperfection modes were studied,respectively.Firstly,4 typical initial geometric imperfection modes including consistent defect mode1,consistent defect mode2,characteristic value defect mode and first order vibration shape defectmode were chosen from related literatures,their theoretical calculation formulas and the method to apply them to ideal reticulated shells were introduced.Secondly,through the finite element modeling analysis,deformation and natural frequency changes of single-layer reticulated shells with four initial geometric imperfection modes were investigated.Finally,four initial geometric defect modes were applied to single-layer spherical reticulated shells with span of 100 m and other different parameters,respectively,and seven 3-D ground motion records selected from the main earthquake of Tangshan earthquake were input to perform dynamic time history analysis.The effects of four initial geometric imperfection modes on the dynamic performance and load-bearing capacity of single-layer latticed shells were investigated.The results showed that for the single-layer spherical latticed shell with a rise to span ratio of 1/3,the maximum node displacement of the shell with consistent defect mode1 exertedis larger;for single-layer latticed shells with other parameters,the maximum node displacement of the shell with characteristic value defect mode exerted is larger;this study can provide a reference for the dynamic performance analysis of single-layer latticed shells and choosing the most unfavorable initial geometric imperfection mode when considering earthquake action in structural design.