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(a) Reduction in wall thickness as a percentage of the original wall thickness. (b) Distribution of failure parameter (combination of stress and joint rotation) with (blue) and without wall thickness reduction (orange) for AC pipes.
Source publication
Comsima is a mechanical model that calculates stresses and joint rotations in drinking water distribution pipes based upon several loadings on the pipe (soil, traffic, water pressure, differential settlements). Pipe degradation mechanisms (slow crack growth resistance for PVC and calcium leaching for AC) were added to the model. A comparison with f...
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Citations
... The results showed that there is a strong relationship between the annual number of failures and the frequency and intensity of low temperatures. Wols et al. (2018) Pipe failure in WDNs was predicted by COMputation of Stresses in MAins (COMSiMA). COMSiMA is a mechanical model that calculates stresses and joint rotations in WDNs based upon several loadings on the pipe (soil, traffic, water pressure, differential settlements) (Wols et al. 2018). ...
... Wols et al. (2018) Pipe failure in WDNs was predicted by COMputation of Stresses in MAins (COMSiMA). COMSiMA is a mechanical model that calculates stresses and joint rotations in WDNs based upon several loadings on the pipe (soil, traffic, water pressure, differential settlements) (Wols et al. 2018). The result showed that pipes with higher stresses or higher joint rotations, in general, have a higher failure rate. ...
Periodic surface inspections of Water Distribution Networks (WDNs) buried in the soil aren’t possible. Failures, leakage or malfunctioning to these networks usually appear when they have happened, and, therefore, it is essential to get knowledge about the causes of events to increase the used structures’ lifespan. With the spatial nature and parameters uncertainty of the WDN, it is possible to analyze its events using a Geospatial Information System (GIS) and Fuzzy Logic (FL). This paper provides a framework for spatial analysis and assessing the risk of failure in the pipe networks using a Fuzzy Inference System (FIS) based on past events spatial information. Parameters such as Number of Previously Observed Breaks (NPOBs), material, age, length and diameter of pipes were selected as factors for the determination of failure risk zones in urban WDNs. Results showed that the material factor is the most important (with a share of 22%) in pipe failure, followed by length, age, and diameter. The Root Mean Square Error (RMSE) for application of the method on the test data of Tuyserkan city, Iran was 0.38.
... The results showed that there is a strong relationship between the annual number of failures and the frequency and intensity of low temperatures. Wols et al. (2018) Pipe failure in WDNs was predicted by COMputation of Stresses in MAins (COMSiMA). COMSiMA is a mechanical model that calculates stresses and joint rotations in WDNs based upon several loadings on the pipe (soil, traffic, water pressure, differential settlements) (Wols et al. 2018). ...
... Wols et al. (2018) Pipe failure in WDNs was predicted by COMputation of Stresses in MAins (COMSiMA). COMSiMA is a mechanical model that calculates stresses and joint rotations in WDNs based upon several loadings on the pipe (soil, traffic, water pressure, differential settlements) (Wols et al. 2018). The result showed that pipes with higher stresses or higher joint rotations, in general, have a higher failure rate. ...
Periodic surface inspections of Water Distribution Networks (WDNs) buried in the soil aren’t possible. Failures, leakage or malfunctioning to these networks usually appear when they have happened, and, therefore, it is essential to get knowledge about the causes of events to increase the used structures’ lifespan. With the spatial nature and parameters uncertainty of the WDN, it is possible to analyze its events using a Geospatial Information System (GIS) and Fuzzy Logic (FL). This paper provides a framework for spatial analysis and assessing the risk of failure in the pipe networks using a Fuzzy Inference System (FIS) based on past events spatial information. Parameters such as Number of Previously Observed Breaks (NPOBs), material, age, length and diameter of pipes were selected as factors for the determination of failure risk zones in urban WDNs. Results showed that the material factor is the most important (with a share of 22%) in pipe failure, followed by length, age, and diameter. The Root Mean Square Error (RMSE) for application of the method on the test data of Tuyserkan city, Iran was 0.38.
... Ultimately, they found that the results of LS-SVM were more accurate than those obtained by Feed Forward Neural Network (FFNN) and Generalized Regression Neural Network (GRNN) techniques. Wols et al. (2018) used a mechanical technique, introduced as Comsima, to compute the break rate with consideration of stresses and joint rotations in a part of WDN in the Netherlands based on quite a few loading conditions on the pipe (i.e., soil, traffic, water pressure, and differential settlements). Robles-Velasco et al. (2020) applied Logistic Regression (LR) and Support Vector Classification (SVC) to evaluate the pipe breaks in a part of WDN, Spine. ...
An accurate prediction of pipes failure rate plays a substantial role in the management of Water Distribution Networks (WDNs). In this study, a field study was conducted to register pipes break and relevant causes in the WDN of Yazd City, Iran. In this way, 851 water pipes were incepted and localized by the Global Positioning System (GPS) apparatus. Then, 1033 failure cases were reported in the eight zones of understudy WDN during March-December 2014. Pipes break rate (BRP) was calculated using the depth of pipe installation (hP), number of failures (NP), the pressure of water pipes in operation (P), and age of pipe (AP). After completing a pipe break database, robust Artificial Intelligence models, namely Multivariate Adaptive Regression Spline (MARS), Gene-Expression Programming (GEP), and M5 Model Tree were employed to extract precise formulation for the pipes break rate estimation. Results of the proposed relationships demonstrated that the MARS model with Coefficient of Correlation (R) of 0.981 and Root Mean Square Error (RMSE) of 0.544 provided more satisfying efficiency than the M5 model (R = 0.888 and RMSE = 1.096). Furthermore, statistical results indicated that MARS and GEP models had comparatively at the same accuracy level. Explicit equations by Artificial Intelligence (AI) models were satisfactorily comparable with those obtained by literature review in terms of various conditions: physical, operational, and environmental factors and complexity of AI models. Through a probabilistic framework for the pipes break rate, the results of first-order reliability analysis indicated that the MARS technique had a highly satisfying performance when MARS-extracted-equation was assigned as a limit state function.
... In previous work, it was determined that X-ray computed tomography may indeed provide a detailed description of AC pipe degradation [15]. In that work, it was also revealed that the leaching of AC drinking water pipes occurs in a far less homogeneous way than is traditionally assumed [16][17][18]. ...
... However, the technique unlocks the possibility to study the degradation phenomena that occur in AC in more detail. At the current state of knowledge, homogeneous degradation at a constant rate is typically assumed [17,18]. According to the results presented in Section 3.1, this assumption represents an exception rather than a rule, as inhomogeneous degradation was prevalent at both the inner and the outer pipe wall. ...
The water distribution network of the Netherlands contains around 30,000 km of asbestos cement (AC) pipes, which constitutes around 25% of the total network. As a pipe material, AC has a relatively poor performance, and therefore is a high priority for renewal. To help decide an effective order of replacement, the water utilities need condition assessment techniques that help them determine which pipes have the highest risk of failure. In the presented work, X-ray computed tomography (CT) was used to measure the degradation of AC pipes taken out of the field. These scans provide a description of the pipe degradation with unmatched detail. The results are compared with strength tests performed on the same pipes, revealing that detailed knowledge of the complete pipe degradation is more important than previously assumed. Moreover, comparison of the CT results to those of a commercial, non-destructive inspection technique was used as a new avenue for validation of this technique, demonstrating its future usefulness for attaining the detailed measurement of pipe degradation required by water utilities.
... For example, the author of [11,12] stated, using the example of a pipe route failure, that even a small-scale failure can cause the collapse of the entire system and affect the performance of the entire water network. Other approaches to the evaluation of water supply networks are also presented by the authors of the publication [13,14], who, in their work, evaluate individual components of the water supply network on the basis of graph theory and also deal into detail with the issue of risky urban water supply networks analysis, as well as other publications [15][16][17][18][19]. ...
In this study, we investigated the modelling and optimization of drinking water supply system reliability in the village of Zaben, Czech Republic. An in depth overview of the water supply network in the municipality, passport processing and accident and malfunction recording is provided based on data provided by the owner and operator of the water mains as well as the data collected by our own field survey. Using the data processed from accident and failure reports in addition to water main documentation, the water supply network in Zaben was evaluated according to the failure modes and effects analysis methods. Subsequently, individual water supply lines were classified based on their structural condition. In addition, a proposed plan for financing the reconstruction of the water supply mains in Zaben was created. As such, this study provides an overall assessment of the water supply network in Zaben alongside a proposed plan for the structural restoration of the water supply system, which accounts for the theoretical service life of the system and the financial resources of the owner.
... Presumably, the localized nature of the external degradation in Figures 2 and 3 is related to the corresponding distributions of aggressive soil components around the pipe when the pipes were in use. The inhomogeneous nature of the internal degradation is more remarkable, however, since the leaching of calcium hydroxide from the AC pipes into the drinking water is typically understood to be a diffusion-controlled process that occurs homogeneously across the pipe surface [6]. Nonetheless, the patterns described above were typical for the 32 pipes that were scanned in total. ...
The Dutch drinking water distribution network consists roughly of 25% (around 30,000 km) asbestos cement pipes. This pipe material has a relatively high priority to be renewed and therefore received quite some attention when it comes to the development of condition assessments that help water utility experts to prioritize which of these pipes to replace first. In the presented work, X-ray computed tomography (CT) was used to measure the degradation of the asbestos cement (AC) pipes taken out of the field. The CT scans provide a highly detailed view of the pipe degradation. The insight provided by these images poses several questions with respect to some of the core assumptions of the condition models currently in use. Moreover, the comparison of CT results to those of non-destructive, in-line inspection techniques will provide a new avenue for the validation of these techniques and their usefulness for the Dutch water utilities.
... As presented in a companion paper at this conference [1], KWR uses the computational tool Comsima (COMputation of Stresses In MAins) to simulate the condition of the distribution network. Comsima combines physical models of loading and degradation with Monte Carlo methods to translate a description of a main and its environment to an approximation of its physical state, including uncertainties. ...
The failure of joints plays an important role in the overall performance of mains. One of the prevalent failure modes at polyvinyl chloride (PVC) joints is the rupture of pipe or joint, which may occur due to high angular deflection of the pipe with respect to the joint, caused by differential soil settlement. The present paper reports the construction and use of a finite element model to determine the maximum angular deflection of a variety of PVC joints in different loading situations. The resulting acceptable deflections vary between 3° and 8° per side, which differs significantly from installation guidelines. The results will support drinking water companies in substantiating the prioritization of maintenance and inspection.
Deterioration of urban Water Distribution Networks (WDNs) is one of the primary cases of water supply losses, leading to the huge expenditures on the replacement and rehabilitation of elements WDNs. An accurate prediction of pipes failure rate play a substantial role in the management of WDNs. In this study, a field study was conducted to register pipes break and relevant causes in the WDN of Yazd City, Iran. In this way, 851 water pipes were incepted and localized by the Global Positioning System (GPS) apparatus. Then, 1033 failure cases were reported in the eight zones of under study WDN during March-December 2014. Pipes break rate ( BR P ) was calculated using the depth of pipe installation ( h P ), number of failure ( N P ), pressure of water pipes in operation ( P ), and age of pipe ( A P ). After completing a pipe break database, robust Artificial Intelligence models, namely Multivariate Adaptive Regression Spline (MARS), Gene-Expression Programming (GEP), and M5 Model Tree were employed to extract precise formulation for the pipes break rate estimation. Results of the proposed relationships demonstrated that MARS model with Coefficient of Correlation (R) of 0.981 and Root Mean Square Error (RMSE) of 0.544 provided more satisfying efficiency than M5 model (R = 0.888 and RMSE = 1.096). Furthermore, statistical results indicated that MARS and GEP models had comparatively at the same accuracy level. Explicit equations by AI models were satisfactorily comparable with those obtained by literature review in terms of various conditions: physical, operational, and environmental factors and complexity of AI models. Through a probabilistic framework for the pipes break rate, the results of first-order reliability analysis that MARS technique had highly satisfying performance when MARS-extracted-equation was assigned as a limit state function.
This paper gives an overview of the asset management landscape on drinking water in the Netherlands and twenty years of research on this topic executed by KWR in close collaboration with water companies. A description is given of research questions and the international developments in the field of asset management. This is followed by the developments on asset management at the Dutch water company Evides. Twenty years of asset management research at KWR is presented in five phases, showing a transition from the question how can the concepts of asset management help to better plan the replacement of distribution networks, towards integrated decision making on the asset system as a whole. A focal point for research could be how research can contribute creating value for water companies. More formal information and improved modelling will continue to play a central role, however attention is required for making use of expert knowledge, scenario building, data quality and the integration of information of technical, financial and societal origin.
Pipe failure data provides valuable information on the mechanisms and conditions which cause drinking water pipes to break or leak. Such data feeds asset management models, helping water utilities to decide future interventions at different timelines. Among countries, and even within countries, utilities apply different pipe failure data collection methods, for a-posteriori analyses. This contribution focuses in the comparison of pipe failure data collection methods and practices in three countries: Japan, Sweden and The Netherlands. We compare their methodologies and the use that such data is given. We identify the potential for knowledge transfer of methods between the three countries. This paper stems from the Watershare knowledge sharing platform, where the three organizations are active members, along with 17 other knowledge institutes spread across the world.
