Spatial-temporal reliability analysis of corroding cast iron water pipes

Destructive effects of pipeline structural failure on the worldwide social, environmental and financial aspects reveal the importance of accurate reliability assessment of these infrastructures. In this research, the structural integrity of water cast iron pipes is assessed by a spatial-temporal reliability analysis. Random field representation is used for taking the spatial variability of corrosion depth into account. A probabilistic model for correlation length of corroded cast iron surfaces is developed using the data collected from in-service pipe samples in the West of Melbourne, Australia. To this aim, the randomness associated with involved parameters in the deterioration process is acknowledged by Monte Carlo simulation, and limit states criteria are checked for individual failure mode and also for combination of them in order to execute a multi-failure mode reliability assessment for finding the likelihood of the time of pipeline failure

Structural failure assessment of buried steel water pipes subject to corrosive environment

It is essential to predict the lifetime of buried pipelines since they are not easily accessible for inspection. In this study a time-dependent, non-linear state model has been introduced for the structural analysis of corrosion affected steel water pipes, stressed by external forces. Using limit state concept, the simultaneous effect of externally applied loading and material corrosion are considered through failure modes. A nonlinear corrosion model is used to simulate the loss of pipe wall thickness during the operation period. In order to take the uncertainty associated with the design and environmental variables into account, a Monte Carlo simulation technique has been adopted using MATLAB. A parametric sensitivity analysis is also carried out to measure the effectiveness of each parameter on the probability of pipe failure. Results obtained for a steel water pipeline in Eastern Sydney are presented and discussed

''Nearest zero-point'' algorithm for cooperative robotic search missions

Four path planning and data exchange algorithms for cooperative search and coverage robotic missions are proposed and modified. The introduced methods are simulated using C++ programming environment and the results are discussed in detail for environments with static obstacles. It has been shown that using the "nearest zero-point" algorithm can greatly optimise the mission duration and also overlapping of the search trajectories. Finally, the results are compared with several existing algorithms

Durability of concrete sewers: monitoring, assessment and improvement

The durability of concrete sewer pipes is affected by a variety of degradation mechanisms such as sulphuric acid, chloride and sulphate attack. The problem of degradation of concrete sewer pipes has been a growing problem as these infrastructure assets age. The destructive mechanisms can vary due to increase in the environmental factors such as acidity and temperature. This study aims to investigate and compare the current monitoring and assessment methods for concrete sewers with suggestions for improving their durability. The results of a comprehensive lab experiment in the UK for investigating the combined effect of temperature and acidity on concrete durability is also reviewed. The study also highlights the areas of research which need to be addressed for more sustainable concrete sewer systems (in terms of materials as well as management)

Structural reliability analysis of corroding steel bridges using random-field representation

The functional safety of steel bridges is of great importance for governments and infrastructure managers. This functionality is, however, affected by natural aging and environmental threads such as corrosion. Corrosion can play major role in steel bridge failure; mainly by reducing the thickness of bridge girders or by forming pits on the steel surface which consequently affects the structural integrity of the bridge. In this study, an innovative technique for representation of corrosion has been used when applying a multi-failure reliability analysis method. To this aim, the distribution of corrosion pits is modelled by a 2D random field and then, the generated surface is incorporated with a Monte-Carlo reliability analysis method to predict the service life of in-service steel bridge girders

Time-dependent finite element reliability assessment of cast-iron water pipes subjected to spatio-temporal correlated corrosion process

© 2020 Reliable prediction of the service-life of water pipes is of great importance for asset managers and decision makers. This paper introduces a framework for evaluating the reliability of corroded pipelines. Incorporating the random field representation of corrosion into a finite-element analysis have always been a daunting task especially when the time-dependent reliability analysis is intended. This research addresses the issue by representing the cross-section reduction of a buried pipe due to corrosion through a combination of the Gamma process concept and copula. Moreover, spatial and temporal evolutions of the correlation structure that exists among the corrosion pits over the pipe surface are considered using a time-dependent correlation length model recently introduced by the authors. A three-dimensional non-linear finite element analysis is used to model the residual strength of pipes in terms of time. The method is applied to a case study for estimating the failure probability of a corrosion-affected cast iron water pipe. Furthermore, the impact of the correlation structure of the corrosion depths on the estimated probability of failure is investigated. The research concludes that the proposed method is able to predict the service life of corroding buried pipeline efficiently

Recent Advances in Sensing and Assessment of Corrosion in Sewage Pipelines

Corrosion is known as the gradual destruction of materials, leading to structural integrity loss and deteriorates the surface function. Regarding sewage pipelines, corrosion is vital due to its substantial financial, health, and safety costs for society, and it is considered as one of the biggest problems facing water and wastewater infrastructure. Also, it is the primary cause of chemical property alteration, efficiency loss, life span reduction, etc. To overcome the resulting problems, various researches have been performed to understand not only the effective parameters leading to corrosion in sewer pipes but also monitoring the infrastructure conditions. Studies have depicted that developments in sensing systems to detect effective parameters in pipe corrosion such as temperature, H2S, and pH, have significantly reduced damage to the industrial equipment of sewage pipelines caused by corrosion. This paper presents a critical review of the effective factors resulting in sewer pipeline corrosion and discusses advanced sensing systems utilized for relevant monitoring. Also, microbiologically induced corrosion and effective factors are individually discussed. Moreover, various data analysis techniques adopted to evaluate outputs of the sensors for corrosion prediction have been explored. Finally, recommendations and future directions for improving sensing accuracy and robustness are detailed