基于非概率集合理论的屋面板风致疲劳寿命估计

FATIGUE LIFE ANALYSIS OF PANELS UNDER WIND LOAD BASED ON NON-PROBABILISTIC SET THEORY

现有疲劳分析中,通常将结构材料参数、几何尺寸等定义为确定性参数;实际结构中,相关参数均为有界但不确定变量,如按确定性参数估计结构的疲劳寿命是偏于不安全的。该文将结构体系中不确定参数定义为区间变量,在线性疲劳损伤累积理论基础上,提出一种仅需一次动力响应分析即可计算不确定结构在动力荷载作用下疲劳损伤的新方法。该方法将金属屋面板弹性模量和屋面板板厚等由于施工误差等因素引起的不确定参数定义为区间变量,通过摄动法和区间动力响应分析,计算屋面板在脉动风荷载作用下的应力响应区间;结合屋面板材料的S-N曲线,采用修正Miner疲劳线性累积准则对屋面板的疲劳损伤和寿命区间进行估计。结果表明:该文方法可有效计算考虑结构参数不确定条件下金属屋面板的疲劳损伤和寿命区间;与顶点法比较,该文方法仅需一次动力响应分析就可计算金属屋面板风致疲劳损伤和寿命区间。

In the existing fatigue analysis methods,structural material parameters and geometric dimensions are usually considered to be deterministic variables.For real structures,however,the structural parameters are bounded but uncertain.It is unsafe to estimate the fatigue life of a structure according to the nominal values.In this paper,we apply the interval analysis method based on non-probabilistic set theory to estimating the roof fatigue life under fluctuation wind load.Considering the thickness and elastic modulus of large-span roofs under bounded-but-uncertain circumstances,we calculate the dynamic response range of long-span roof structures under fluctuating wind load by the interval finite element method and interval dynamic response analysis method.The time history curve of the interval stress of large-span roofs is obtained through the constitutive equation and stress.The amplitudes of the interval stress are calculated by the rain-flow counting method.Considering the S-N curve of the roof material,we estimate the fatigue life interval of large-span roofs by Miner's law.