大矢跨比异形单层球壳结构的缺陷稳定性分析

Stability analysis of large rise-span ratio special-shaped single layer spherical shells with imperfections

清远科技馆大矢跨比异形单层球壳,采用肋环型网格形式,跨度24.6m,矢高19.05m,具有矢跨比大、网格布置稀疏、洞口较大、周边外侧与环形框架相连等特点。以该结构为对象,分别采用一致缺陷模态法和随机缺陷模态法,探讨不同初始几何缺陷引入方式对结构稳定承载力的影响。在此基础上,以弯轴应力比为指标,考察结构的受力状态。结果表明:结构对初始几何缺陷不敏感;初始几何缺陷按最低阶屈曲模态分布时,求得的稳定承载力系数并非最小,但其保证率满足“3σ”原则的要求;与常规单层网壳结构不同,该结构的受力状态以弯曲内力为主。

The large rise-span ratio special-shaped single layer spherical shell in Qingyuan Science Museum adopts the form of ribbed-type grid, with its span of 24.6 m and rise of 19.05 m, which has the characteristics of large rise-span ratio, sparse grid layout, big openings and being connected with the ring frame around the outside. Taking this structure as the object, the consistent mode imperfection method and the random imperfection mode method are used respectively to discuss the influence of different initial geometric imperfection introduction modes on the stability bearing capacity of the structure. Based on the study above, the index of bending-axial stress ratio is introduced to investigate the internal force state of the structure. The results show that the structure is insensitive to the initial geometric imperfection. The coefficient of stability bearing capacity usually is not minimal when the initial geometric imperfection is distributed in the first-order buckling mode, but its guarantee rate meets the requirement of ‘3σ’ principle. Different from the conventional single layer reticulated shells, the internal force state of the structure is dominated by the bending force.