Reliability Analysis Method for Degrading Structures Taking Combination of Load Processes into Account

基础设施的恶化是许多国家普遍存在的问题。为了评估这些结构在未来的持续使用，需要开发简单实用的工具来评估结构的时变可靠性和性能。当多个时变荷载作用在结构上时，需要考虑参考期内组合的最大强度。本计画首先发展出组合最大强度累积分布函数的理论表达式。数值算例表明，cdf的理论表达式提供了相当好的估计，而不考虑载荷强度和随机过程的统计特性.然后，由于一个组件的退化阻力减少因子的概念被引入到近似的时间相关的可靠性问题作为一个时间无关的。利用该系数，时变电阻可以等效为 关于我们 提出了一种确定可靠性系数的近似方法，算例表明，采用近似的可靠性折减系数可以较准确地达到目标可靠性水平，通过定期的在役检查和适当的维修，可以使退化的结构构件恢复到接近原始状态。由于检查和维护成本高昂，因此需要在检查的范围和准确性、所需的可靠性水平和成本之间进行权衡。为了设计一个最佳的检查/维护策略，通常必须解决非线性优化问题。近似方法可以应用于估计电阻降低因子，包括当组件的强度由于诸如恢复而随时间不连续地改变时的情况。使用所提出的方法，可以简化优化过程，避免进行时变可靠性分析。少

The deterioration of infrastructures is a widespread problem in many countries. In order to assess such structures for continued future service, simple and practical tools need to be developed for evaluating the time-dependent reliability and performance of the structures.When more than one time-varying load act on a structure, the maximum intensity of the combination during the reference period needs to be considered. This project first developed the theoretical expressions of the cumulative distribution function (cdf) of the maximum intensity of the combination. Numerical examples show that the theoretical expression of the cdf provides fairly good estimate regardless of the statistical characteristics of the load intensity and stochastic processes.Then the concept of a resistance reduction factor due to degradation of a component is introduced to approximate a time-dependent reliability problem as a time-independent one. With the factor the time-varying resistance can be equivalentl … More y replaced with a time-invariant resistance, and load and resistance factors can be determined for the assessment applying simple AFOSM.An approximation method to determine the factor is proposed, and numerical example shows that the target reliability level can be achieved fairly accurately using an approximate reduction factor.Periodic in-service inspection followed by suitable maintenance may restore a degraded structural component to near-original condition. Since inspection and maintenance are costly, there are tradeoffs between the extent and accuracy of inspection, required level of reliability, and cost. To design an optimum inspection/maintenance strategy, generally non-linear optimization problem must be solved. The approximation method can be applied to estimate a resistance reduction factor including the cases when the strength of a component changes discontinuously in time due to, such as, restoration. Using the proposed method, the optimization can be simplified avoiding time-dependent reliability analysis. Less