初始几何缺陷模式对单层球面网壳抗震性能的影响

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.