Reliability of stability of single-layer latticed shells with spatially correlated initial geometric imperfection modeled using conditional autoregressive model
Reliability of stability of single-layer latticed shells with spatially correlated initial geometric imperfection modeled using conditional autoregressive model
复制标题
使用条件自回归模型建模的具有空间相关初始几何缺陷的单层网状壳稳定性的可靠性
DOI：
10.1016/j.engstruct.2019.109787
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发表时间：
2019-12
影响因子：
5.5
通讯作者：
H.P. Hong
中科院分区：
文献类型：
--
作者：
X.Z. Cui;Y.G. Li;H.P. Hong
网壳结构在大跨度结构中有着广泛的应用。它们的设计通常由中国设计规范中规定的指定重力荷载和初始几何缺陷（IGI）的整体失稳要求控制。然而，建议的设计要求（需要达到临界载荷系数2）的可靠性基础是未知的。在本研究中，它提出了空间变化的IGI可以充分利用条件自回归模型建模。结果表明，该模型在模拟空间变化的相关缺陷时具有足够的灵活性，可以科普不规则的网格系统。将该模型应用于IGI网壳结构，考虑整体失稳，计算了按我国规范设计的球面网壳和柱面网壳的承载力概率分布和失效概率。还进行了评估，通过使用空间独立的高斯模型和第一本征屈曲模式（1EBM）的设计规范推荐的IGI形状表示。结果表明，使用的1EBM代表IGI形状不一定会导致保守的估计的故障概率相比，通过考虑空间变化的随机缺陷形状。结果表明，网壳结构的失效概率对网壳结构各节点IGI的随机模型和标准差敏感。此外，球面网壳的失效概率与柱面网壳不同。可靠性分析结果还表明，在网壳设计规范中采用临界荷载系数2时，整体失稳的年失效概率一般小于10−5。灵敏度分析表明，规范建议的临界荷载系数可以降低到1.75，同时达到设计规范校准经常采用的目标可靠性指标。
Latticed shells are extensively used for large-span structures. Their design is often governed by the global instability requirement stipulated in the Chinese design code for the specified gravity load and initial geometric imperfection (IGI). However, the reliability-basis for the recommended design requirement that a critical load factor of 2 need to be achieved is unknown. In the present study, it is proposed that the spatially varying IGI can be adequately modeled using the conditional autoregressive model. It is shown that this model is sufficiently flexible in modeling spatially varying correlated imperfection and can cope with irregular grid systems. By using this model for IGI and considering global instability, the probability distributions of the load capacity and the failure probabilities of spherical and cylindrical latticed shells designed according to the Chinese design code are evaluated. The evaluation is also carried out by representing the IGI shape using the spatially independent Gaussian model and the first eigen buckling mode (1EBM) that is recommended by the design code. It is shown that the use of the 1EBM to represent the IGI shape does not necessarily lead to conservative estimates of the failure probabilities as compared to those obtained by considering spatially varying stochastic imperfection shapes. The results shown that the estimated failure probability is sensitive to the assumed stochastic model for and standard deviation of the IGI at each joint of the latticed shells. Furthermore, the failure probability of the spherical latticed shell differs from that of the cylindrical latticed shell. The reliability analysis results also indicate that the use of a critical load factor of 2 implemented in the code for design of the latticed shell, in general, lead to an annual failure probability for global instability less than 10−5. A sensitivity analysis indicates that the code recommended critical load factor can be reduced to 1.75 while achieving a target reliability index often adopted for design code calibration.
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