Automated defect detection tool for closed circuit television (cctv) inspected sewer pipelines

In sewer networks, the economic effects and costs that result from a pipeline failure are rising sharply. As a result, there is huge demand for inspection and rehabilitation of sewer pipelines. In addition to being inaccurate, current practices of sewer pipelines inspection are time consuming and may not keep up with the deterioration rates of the pipelines. This papers presents the development of an automated tool to detect some defects such as: cracks, deformation, settled deposits and joint displacement in sewer pipelines. The automated approach is dependent upon using image-processing techniques and several mathematical formulas to analyze output data from Closed Circuit Television (CCTV) camera images. The automated tool was able to detect cracks, displaced joints, ovality and settled deposits in pipelines using CCTV camera inspection output footage using two different datasets. To examine the performance of the proposed detection methodology, confusion matrices were constructed, in which true positives for crack, settled deposits and displaced joints were 74%, 53% and 65%. As for the ovality, all defects in the images were detected successfully. Although these values could indicate low performance, however the proposed methodology could be improved if additional images were used. Given that one inspection session can result in hundreds of CCTV camera footage, introducing an automated tool would help yield faster results. Additionally, given the subjective nature of evaluating the severity of defects, it would result in more systematic outputs since the current method rely heavily on the operator's experience.     

Pain and suffering costs of persons in construction accidents: Hong Kong experience

Direct financial costs of accidents are the tip of the iceberg when compared to the indirect costs. Notwithstanding the difficulties involved, it is very important to estimate the indirect costs borne by society, and the non‐material losses due to pain, suffering and loss of enjoyment of life undergone by the victim. This study investigates the pain and suffering costs (non‐material losses) of the victims of construction accidents in Hong Kong based on relevant High Court personal injury case judgements in the years 1999–2003. The 54 non‐fatal accident cases and 14 fatal accident cases analysed indicate that the average percentage of compensation awarded for non‐material damages (pain, suffering and loss of enjoyment of life) to that for material damages (loss of earnings, medical and travelling expenses, etc.) during those years is about 30%. This result enables estimating the pain and suffering costs of the society for a particular year if the total material losses of all construction accidents in that year are known. Based on previous research in which the material losses in Hong Kong were evaluated for the years 1999, 2000 and 2001, the corresponding pain and suffering costs could be estimated as 219 million, 150 million and 107 million Hong Kong dollars, respectively (US$1.00?=?HK$7.80).     

隔震建筑的经济性分析

鉴于目前国内在隔震建筑的经济性方面缺乏详细的分析,使得一些业主对隔震建筑在“投资-效益比”方面有些错误的印象,本文从直接建设费和震后损失及维修费用两方面对隔震建筑做了经济性分析。用4个不同情况的隔震工程,比较了隔震与不隔震时各项直接建设费用的增减情况,分析结果表明,对一般建造于抗震设防高烈度区的钢筋混凝土框架或框架剪力墙丙类建筑,采用隔震措施比采用传统抗震措施可降低直接建设费用约1％-5％。利用相关文献中提供的数据,比较了隔震与不隔震时震后损失及维修费用的减小程度,计算结果表明,采用隔震后一般可减小损失及维修费用约8％-35％。因此,隔震建筑具有传统抗震建筑无法比拟的经济性。     

Multiobjective optimisation algorithm for sewer network rehabilitation

Understanding of deterioration mechanisms in sewers helps asset managers in developing prediction models for estimating whether or not sewer collapse is likely. Effective utilisation of deterioration prediction models along with the development and use of life cycle maintenance cost analysis contribute to reducing operation and maintenance costs in sewer systems. This article presents a model for life-cycle maintenance planning of deteriorating sewer network as a multi-objective optimisation problem that treats the sewer network condition and service life as well as life-cycle maintenance cost (LCMC) as separate objective functions. The developed model utilises Markov chain model for the prediction of the deterioration of the network. A multi-objective genetic algorithm is used to automatically locate an appropriate maintenance scenario that exhibits an optimised tradeoff among conflicting objectives. Monte Carlo simulation is used to account for LCMC uncertainties. The optimisation algorithm provides an improved opportunity for asset managers to actively select near-optimum maintenance scenario that balances life-cycle maintenance cost, condition and service life of deteriorating sewer network. A case study is used to demonstrate the practical features of developed methodology.     

Attention-guided multiscale neural network for defect detection in sewer pipelines

Sanitary sewer systems are major infrastructures in every modern city, which are essential in protecting water pollution and preventing urban waterlogging. Since the conditions of sewer systems continuously deteriorate over time due to various defects and extrinsic factors, early intervention in the defects is necessary to prolong the service life of the pipelines. However, prior works for defect inspection are limited by accuracy, efficiency, and economic cost. In addition, the current loss functions in object detection approaches are unable to handle the imbalanced data well. To address the above drawbacks, this paper proposes an automatic defect detection framework that accurately identifies and localizes eight types of defects in closed-circuit television videos based on a deep neural network. First, an effective attention module is introduced and used in the backbone of the detector for better feature extraction. Then, a novel feature fusion mechanism is presented in the neck to alleviate the problem of feature dilution. After that, an efficient loss function that can reasonably adjust the weight of training samples is proposed to tackle the imbalanced data problem. Also, a publicly available dataset is provided for defect detection tasks. The proposed detection framework is robust against the imbalanced data and achieves a state-of-the-art mean average precision of 73.4%, which is potentially applied in realistic sewer defect inspections.     

Probabilistic Neural Network for Reliability Assessment of Oil and Gas Pipelines

A fuzzy artificial neural network (ANN)–based approach is proposed for reliability assessment of oil and gas pipelines. The proposed ANN model is trained with field observation data collected using magnetic flux leakage (MFL) tools to characterize the actual condition of aging pipelines vulnerable to metal loss corrosion. The objective of this paper is to develop a simulation-based probabilistic neural network model to estimate the probability of failure of aging pipelines vulnerable to corrosion. The approach is to transform a simulation-based probabilistic analysis framework to estimate the pipeline reliability into an adaptable connectionist representation, using supervised training to initialize the weights so that the adaptable neural network predicts the probability of failure for oil and gas pipelines. This ANN model uses eight pipe parameters as input variables. The output variable is the probability of failure. The proposed method is generic, and it can be applied to several decision problems related with the maintenance of aging engineering systems.     

Sewer asset management – state of the art and research needs

ABSTRACT

Sewer asset management gained momentum and importance in recent years due to economic considerations, since infrastructure maintenance and rehabilitation directly represent major investments. Because physical urban water infrastructure has life expectancies of up to 100 years or more, contemporary urban drainage systems are strongly influenced by historical decisions and implementations. The current decisions taken in sewer asset management will, therefore, have a long-lasting impact on the functionality and quality of future services provided by these networks. These decisions can be supported by different approaches ranging from various inspection techniques, deterioration models to assess the probability of failure or the technical service life, to sophisticated decision support systems crossing boundaries to other urban infrastructure. This paper presents the state of the art in sewer asset management in its manifold facets spanning a wide field of research and highlights existing research gaps while giving an outlook on future developments and research areas.     

An economic valuation model for alternative pressure management schemes in water distribution networks

Pressure management (PM) is commonly used in water distribution networks (WDNs) to provide a wide range of benefits. This study presents an economic evaluation framework to support the decision-making process relating to alternative PM schemes. The methodology allows for the assessment the principal direct and indirect benefits and costs associated with using pressure-reducing valves (PRVs). The methodology is applied to a district metered area in a WDN in Mashhad, Iran, by changing the existing fixed–outlet (FO-PRV) to time-based (TM-PRV) and flow-based modulation (FM-PRV). The results indicated that FM-PRV is the most beneficial scheme for the studied case. The importance of estimating direct and indirect benefits is highlighted. The presented methodology is essential to persuade water utility decision-makers to recognize the economic feasibility and significant benefits of implementing PM schemes and justify the associated investment.     

Life cycle cost of flexible pavements and climate variability: case studies from Virginia

Abstract

Climate factors have not become a typical metric to consider for pavement life cycle cost analysis (LCCA). Changes in climate may affect pavement rutting, roughness, and cracking and lead to consequent changes in maintenance decision-making and life cycle costs. This study develops a methodology to incorporate the effects of climate variability into flexible pavement LCCA and to derive the additional life cycle costs incurred due to changes in climate. Case studies were performed for three road sections in Virginia (US) to demonstrate the methodology, using approximate mean climate change trends predicted for the investigated regions. It is estimated that climate change will incur additional vehicle operating costs ranging between US$2.30 and $4.40 on average per vehicle/annum if roads are used under a 2050 high greenhouse gas emission scenario and without being maintained. Assuming responsive maintenance, the budget demand for maintenance will arrive much earlier in the pavements’ life cycles (7–11?years earlier under the 2050 high-emission scenario). This is found to add up to 64% of agency costs (net present value) to repair each kilometre of the investigated roads in a 40-year design life. Agencies need to be aware of earlier or more frequent demands on their maintenance budgets.     

Statistical comparison of the performance of data-based models for sewer condition modeling

Abstract

The present article proposes a methodology to consider the uncertainty intrinsic to data-based models when comparing their performance. The goal is to provide a quantification of the variability of this type of models due to the random nature of the calibration process and enable a statistical comparison of the models’ performance when attempting to identify the best. The methodology proposed doesn’t provide an alternative metric to determine the models’ performance, but it expands the traditional deterministic comparison to a stochastic comparison. The methodology builds on the current standard approach for developing data-based model and its application is demonstrated to model sewer condition using data from 4 trunk sewers of the SANEST – Saneamento da Costa do Estoril sewer system, corresponding to 25?km of sewer pipes. The data-based models were developed using artificial neural networks, support vector machines, bootstrapping aggregation and least squares support vector machines. For the case study, the highest and average misclassification performance records are similar for all models (23% to 24% and 31% to 33%, respectively) but the lowest performance varied more significantly (39% to 62%). This demonstrates that selecting a model based on its maximum single realisation performance alone may be misleading.     

Cost-benefit evaluation of self-centring concentrically braced frames considering uncertainties

Self-centring concentrically braced frame (SC-CBF) systems have been developed to reduce post-earthquake damages in braced frames. However, due to special details required by the SC-CBF system, the construction cost of an SC-CBF is expected to be higher than that of a conventional CBF. In this study, the seismic performance and economic effectiveness of two prototype buildings utilising SC-CBFs are assessed and compared with buildings utilising conventional CBFs by evaluating the annual probabilities of exceeding various damage levels, expected annual losses, life cycle costs (under seismic hazard) and economic benefit of using SC-CBFs considering prevailing uncertainties. The results of this study show that the SC-CBF buildings have lower drift-related losses but higher acceleration-related losses. The SC-CBF is found to be beneficial for the 6-storey configuration, but not for the 10-storey configuration. For the 6-storey buildings studied here, if the construction cost of the SC-CBF is assumed to be twice that of the CBF, the pay-off time is expected to be 12 to 21 years, with a probability of 68%, considering the uncertainties in the demand, capacity, loss parameters and initial construction costs. Finally, appropriate probabilistic engineering demand parameter model formulation is critical for generating accurate loss analysis results.     

Cost–benefit analysis of constructing a filtration plant for the National Water Carrier in Israel

The paper presents an economic cost–benefit analysis (CBA) of the construction of a filtration plant for the Israeli National Water Carrier (NWC). Its main contribution lies in the comparison between the costs and the benefits of filtration in the context of a concrete policy choice. The first part of the paper presents a cost analysis of two alternative engineering systems: central filtration and localized filtration. The analysis shows that the costs of constructing and operating a central filtration plant are significantly lower than those of a system of local plants. The second part of the paper presents a two‐stage method for assessing the benefits of filtration. First, we valuate the damages caused by consumption of unfiltered water; then we estimate consumers' willingness to pay (WTP) for improved water quality, taking into account households' potential risk aversion. The main result is that total WTP significantly outweighs the costs of constructing and operating the plant.     

Grow up and face the real world [manpower costs estimation]

Manpower costs are usually a major part of total costs, yet manpower costs are often estimated using an unreliable principle instilled into pupils at junior school. Here, the author describes how it is vital to be aware of the consequences of anything that affects the total number of man-hours used. He argues that failure to estimate manpower costs correctly will result in failure to predict profit correctly     

Developing a procurement path determination chart SEM-based approach

The choice of an appropriate procurement system is crucial to construction project success. Procurement selection is largely based on path determination charts, with at least eight key criteria needing to be weighted by decision-makers. Including certain criteria whilst ignoring client-borne transaction costs (TCs) resulting from environmental uncertainties simplifies this process. TCs are ‘unseen’ costs associated with pre- and post-contract work. The effects of uncertainties in the transaction environment and procurement systems on TCs are investigated, comparing the traditional and design-build procurement systems. A cross-sectional sample approach was deployed, involving survey questionnaire and results verification through ‘real-world’ cases. Data was sought from construction professionals in management, design and operation of construction projects. The research participants evaluate their time spent on procurement activities using a five-point Likert scale. Hypotheses of the relations between environmental uncertainties, procurement systems, and pre- and post-contract TCs are tested using a structural equation modelling (SEM) approach. The study found that TCs account for about 46.75% and 42.88% of the daily time spent by project managers in traditional and design-build procurement systems in New Zealand respectively. The study concludes that the TC concept is a useful framework for determining objective instead of subjective opinions for procurement decisions.     

An asset-management model for use in the evaluation and regulation of public-lighting systems

In this paper, an asset-management model is proposed to address challenges facing regulators, managers, and operators of public-lighting systems and suggest optimal performance strategies. A new method is presented to estimate the failure rate of lamps based on the normal distribution function. The impact of technology improvement in lamp manufacturing as well as the growth and extension of lighting systems on the failure rate are investigated. In order to achieve satisfaction of customers and risk reduction, a method for establishing a performance standard for lamp failure rates is presented. Considering technical and economic issues, a procedure for selecting the best lamp in the market and then estimating costs associated with system operation is described. Finally, a methodology is proposed for evaluating performance in public-lighting systems. Results of a case study for the public-lighting system of the newly constructed suburb of the city of Isfahan, Iran, show the efficacy of the proposed method.     

Optimal maintenance strategies for bridge networks using the supply and demand approach

This paper presents a probability-based approach for optimising the management of bridge networks. Most of the Bridge Management Systems are focused on condition features to ensure a minimum safety level for each individual bridge. Their location on the road network, the consequences of inadequate service due to maintenance actions are therefore not taken into consideration. These multiple criteria should be considered when scheduling maintenance activities. To overcome these limitations, a probabilistic supply and demand strategy is proposed for determining the optimal maintenance planning for each interconnected bridge. The problem is solved with genetic algorithms. One objective function is first introduced, corresponding to the summation of all the maintenance, failure, and user costs. Then, two conflicting objective functions are considered, the total user costs and the maintenance and rehabilitation costs. Safety and serviceability aspects are taken into account in the methodology and the theoretical and numerical developments are applied on a part of the French national network.     

Quantifying costs and lengths of urban drainage systems with a simple static sewer infrastructure model

A generic model is introduced that is capable of quantitatively representing the combined sewer infrastructure of a settlement. It consists of a catchment area module, which calculates the length and size distribution of the needed sewer pipes on the basis of rain, housing densities and area size. These results are fed into the sewer construction costs module in order to estimate the combined sewer costs of the entire catchment area.

The model could be successfully fitted to existing Swiss sewer systems, indicating that it can emulate their principal characteristics. It could also identify fundamental differences in sewer designs in cities with historic roots. The results confirm that there are economies of scale for combined sewer systems in Switzerland. The modelling approach proved to be an effective tool for understanding the factors underlying the cost structure for water network infrastructures.     

Experiences with benchmarking of sewerage systems with a special focus on investment costs

In February 2002 an Austrian benchmarking project was completed. The present paper reports on the part of the project dealing with benchmarking of sewerage systems, with a focus on the analysis of investment costs of 34 sewerage system projects. The paper explains the methodology used to make the investment costs of the projects comparable. This was based on an analysis of the final accounts of the finished projects. The paper further delineates the results of the project and considers in detail the important influence of unquantifiable factors, such as economic fluctuations and tendering strategies of the successful contractors, on the calculation of the construction costs.     

Risk-based asset management: automated structural reliability assessment of geographically distributed pipeline networks for gas and water in the Netherlands

Pipeline networks for gas and water are the lifelines of our society. Most pipelines are buried, which obstructs direct monitoring of the pipes, and introduces the need for other techniques to provide network operators with information on the structural reliability of their network. One of the threats related to pipelines, possibly jeopardising the integrity of the network, is deformation of the subsurface surrounding the pipes, which imposes stress in the pipes. This paper describes the development of a fully computerised and automated model to calculate the probability of failure caused by subsurface deformation of pipes over time in the Netherlands. The objective is to provide failure probability information to network operators assisting the decision-making process regarding preventive measures, such as timely replacement. It will result in a reduction of costs associated with pipe failure, and lead to increased safety (e.g. explosion hazard) and certainty of delivery. The methodology used to develop the model is denoted as the STOOP system-of-systems. First results of the model are presented for a case study and show that different data sources and different models can be combined into a system of systems capable of performing predictive assessments.