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Abstract The performance of civil infrastructure systems is vital in supporting a community’s functionalities. Reliability assessment of these systems is a powerful approach to evaluate whether the system performance is desirably safe under the impacts of resistance degradation and non-stationary loads. A k-out-of-n system is a widely-used logic model for a system with n components, which survives (works) if at least k components work. Its special cases include a series or a parallel system. Furthermore, a weighted k-out-of-n system has components with positive integer weights and the system survives if the total weight of working components reaches the predefined threshold k. This paper proposes a method for estimating the time-dependent reliability of both ordinary and weighted k-out-of-n systems, taking into account the effects of resistance deterioration, resistance correlation and load non-stationarity, for which a mathematical solution is derived. The applicability of the proposed method is illustrated through reliability evaluation of a representative k-out-of-n system.

Civil infrastructure systems provide physical supports to a community’s functionalities and are expected to achieve acceptable safety levels subjected to extreme load effects. However, these systems may deteriorate with time as a result of aggressive environmental or operating conditions in service, implying that the system reliability may decline beyond the baseline as assumed for design. Moreover, the increasing trend of the external loads may also contribute to the reduction of the system reliability. In this paper, a semi-analytical method is proposed for assessing the reliability of aging systems subjected to non-stationary loads. The series system is considered, where the system failure is defined as the failure of any single component (structure) among the system. The application of the proposed method is illustrated using a representative series bridge network with several individual bridges. The role of parameters such as the variations in the load intensity, resistance correlation and number of components under attack in the system reliability are investigated. [ABSTRACT FROM PUBLISHER]

In recent years, a rapid pace of climate change is becoming evident by a marked increase in the frequency and intensity of weather extremes, and this trend is expected to continue with an increase in global warming for decades to come. The paper presents the non-homogeneous Poisson process as a basis to model an environmental load process induced by non-stationary climate conditions. The distribution of maximum load generated by a non-stationary process is derived, which explicitly accounts for the loading frequency and intensity amplification over time. Using this distribution, structural reliability can be computed for any given time interval in future. The paper shows that traditional measures like the return period, extreme percentiles, and the annual probability of failure, would vary with time under the changing climate. Examples presented in the paper show that a modest amplification of the load magnitude has a drastic negative effect on reliability than that of the frequency of loading. Probabilistic models presented in this paper will be useful in revising currently used "stationary" design codes and ensuring a consistent level of safety in the non-stationary climate. • Non-homogeneous Poisson process for non-stationary reliability analysis. • Consideration of time-dependent frequency and intensity of applied loads. • An accurate, finite time solution for the non-stationary extreme load distribution. • The concept of the return period is not useful in the changing climate. • A modest load amplification has a major negative effect on reliability. [ABSTRACT FROM AUTHOR]

The time parameters of the spectrum components of non-stationary loading of welded joints of carbon steel were determined, having a dominant influence on the intensity of fatigue fracture of the structural elements of railway locomotives. A new method was offered for analysis of the results of strain gauge measuring of the evolution of deformation heterogeneity in the welded joint HAZ in the process of fatigue crack development. It was established that in each unit of loads at certain frequencies, the deformations exist which are dominant at fatigue fracture. 12 Ref., 5 Figures. [ABSTRACT FROM AUTHOR]

A pulsed impinging jet is used to simulate the gust front of a thunderstorm downburst. This work concentrates on investigating the peak transient loading conditions on a 30 mm cubic model submerged in the simulated downburst flow. The outflow induced pressures are recorded and compared to those from boundary layer and steady wall jet flow. Given that peak winds associated with downburst events are often located in the transient frontal region, the importance of using a non-stationary modelling technique for assessing peak downburst wind loads is highlighted with comparisons. [ABSTRACT FROM AUTHOR]