基于可靠度的单层网壳结构临界稳定承载力计算方法

Reliability-based method for determining of critical stable bearing capacity of single-layer dome structures

为研究基于可靠度的单层网壳结构临界稳定承载力计算方法,选取并改进随机缺陷模态叠加法,作为单层网壳结构初始几何缺陷模拟方法;结合混合阶容积公式,高效准确地计算结构稳定承载力的前四阶统计矩,进一步采用移位广义对数正态分布重构结构稳定承载力概率密度函数;并在给定目标可靠指标或失稳概率下确定单层网壳结构稳定承载力。分别采用六角星网壳模型和K8单层球面网壳结构验证了基于可靠度的临界稳定承载力计算方法的有效性,计算结果表明:采用前四阶屈曲模态叠加所获得的稳定承载力概率分布离散性更大,稳定承载力下降规律与一致模态缺陷法结果基本一致,且现行规范缺陷幅值取跨度的1/300较为保守。

In order to investigate the reliability-based method for determining of critical stable bearing capacity of single-layer dome structures,the random imperfection modal superposition method is applied and modified for the simulation of the initial geometrical imperfections of single-layer dome structures.Then,a kind of mixed-degree cubature formula is developed to evaluate the first-four statistical moments of stable bearing capacity of structures with accuracy and efficiency.Further,the probability density function of stable bearing capacity is reconstructed by using the shifted generalized lognormal distribution,where the critical stable bearing capacity of structures can be specified given the target reliability index or probability of instability.A hexagonal star dome model and a K8 single-layer dome structure are investigated to validate the effectiveness of the proposed method,respectively.The computational results demonstrate that the proposed method uses the superposition of first-four buckling modes to obtain the probability density function of stable bearing capacity with a higher level of variability.The decreasing trend in stability bearing capacity agrees well with the result obtained from the consistent mode imperfection method.Besides,the value of imperfection amplitude in the current code,which is 1/300 of the span,is also quite conservative.