Journal of Pipeline Systems Engineering and Practice

Condition assessment models for sewer network components can be considered a tool for key personnel to make informed decisions regarding the required interventions on the basis of the current conditions of these components. Defect-based models determine the condition of sewer pipelines on the basis of the different defect types and the severity of each defect. In this paper, the different relative weights of defects and components in sewer pipeline segments were determined using the analytical network process (ANP) as an aggregation method. To determine the relative importance of defects and pipeline components, a questionnaire was distributed to experts working in the field of sewage systems and infrastructures. The pipeline segment was divided into three principal components, namely, pipe length, corresponding joints, and manholes, whereas the defects in each component were classified into three defect categories: structural defects, operational defects, and installation/rehabilitation defects. It was found that the pipeline and joint components both had equal relative importance weights of 0.38 each, leaving the manhole component with 0.24. The structural and installation defects’ relative weights for pipelines were higher than the operational defects with a value of 0.4 and 0.36, respectively. The structural defects in joints had the highest share, with 0.61 as a relative weight. The relative defects’ weights in manholes were found to vary between 0.3 and 0.4.

Whereas the continuous functioning of water distribution pipeline systems is important during normal times, it is paramount in the event of disasters such as earthquakes that are usually followed by fire accidents. Past earthquakes resulted in severe damage to water pipelines rendering supply systems dysfunctional in a short period of time. Consequently, it is imperative to make water supply systems sufficiently resilient to seismic hazards in order to ensure better performance and faster recovery after earthquakes. There are several types of resilience metrics that were previously proposed for aiding the seismic resilience enhancement of water supply systems. This paper evaluates two such popular types, namely, topology-based and flow-based metrics, by investigating their respective capabilities in enhancing system resilience to seismic hazards. A serviceability index is defined and used to compare the performances of rehabilitated water systems for each type of resilience metric. A section of a large-scale water supply system that is vulnerable to earthquakes is leveraged in this study for the comparative performance analysis. It is found that the topology-based seismic resilience metric is on average only 80% as efficient as the flow-based metric for the studied water network. Although the flow-based metric seemed relatively superior, it suffers from the need for significant computational time. The resulting trade-off needs to be further investigated using water networks operated in multiple seismic regions.

A field test was performed to study the response of an 800 mm internal diameter, hybrid (plastic/metal) structured wall pipe during installation and varied traffic loading. Synchronized measurements were made of radial soil pressures adjacent to the pipe and pipe deflection, allowing representation of the pressure–deflection relationship of the soil–pipe system. Soil pressures were measured using null pressure measurement cells that avoid the effects of membrane deflection, soil stiffness, and stress history. It is concluded that the critical point in the lifetime of a flexible, shallow buried pipe is when the trench has been backfilled and compacted to the subgrade surface. At this point, the final pavement/asphalt layers have yet to be installed, yet very large loads may be traversing above the pipe section. Once the final pavement layers are constructed, the pressures reaching the pipe crown will become smaller, as will the respective deflections. As a result of the simultaneous and continuous measurement of soil pressure adjacent to the pipe and pipe deflections during the field test, a scheme has been suggested for approximate prediction of flexible pipe deflection in response to traffic loading.

This paper proposes a new method for modeling the behavior of buried steel pipes under reverse faulting. The maximum soil–pipe interaction forces are determined using the results of detailed finite-element analyses that are validated through full-scale laboratory testing of 114.3 and 168.3-mm-diameter steel pipes buried in two different soil types under a reverse fault offset of 0.6 m. The detailed finite-element model is validated through pipe deformation, strain distribution, peak strains, and cross-section distortion. Furthermore, the load-displacement ($q\text{-}z$) curves for the vertical soil springs along with the dimensionless uplift factors are determined and a new formula is proposed. The pipe–soil interaction forces are validated and compared with previous studies and values suggested by different guidelines. The $q\text{-}z$ relations for the uplift forces are found to be more flexible for sections close to the fault plane than are the sections away from the fault plane. Using the proposed model, a validated simple finite-element modeling technique is introduced to simulate the behavior of buried steel pipes under reverse faulting with required accuracy for engineering purposes.

In this paper, true stress–strain curves of two natural gas pipeline steels, API-5L X65 and X90, were studied using the three-dimensional digital image correlation (3D-DIC) technique. During the test, the steels were continuously strained hardening up to the fracture, and true stress–strain curves were obtained. It was found that the true stress increases with strain after necking, which is notably different from the results obtained by the conventional method. Using the FEM model, the true stress–strain curves were validated. Based on the material’s inherent properties, the material property analysis was implemented. The moduli of elasticity in the elastic region obtained by the proposed method and conventional methods were nearly equal. It was also found that the strain-hardening capacities of gas pipeline steels could be better characterized by the hardening exponent than yield-tensile ratio. Besides, the strain-energy density analysis based on the true stress–strain curve demonstrated that before the onset of necking, only 7.3% of the strain energy density of API-5L X90 was used.

Energy-transmission buried pipelines are often susceptible to externally applied concentrated loads that may cause dent defects. A dent or dent defect can be best described as a local defect in the pipe’s wall causing concentration of strains surrounding and within the dent. Additionally, a dent causes the pipe’s diameter to decrease, as well as the reduction in the line’s pressure capacity. Concentration of strains that occur as a consequence of the dent’s formation may lead to a failure such as a leak or a rupture within the pipe’s wall, and this may cause environmental and safety hazards and a loss of revenue for the pipeline operators. Therefore, dent defects are a significant concern for the oil and gas pipeline operators. This paper presents an investigation of the effect of dent length, depth of dent, and operating pressure on the structural performance, distribution of strains, and strain concentrations in oil and gas (energy) transmission pipelines.

One of the challenges of the construction planning stage is selecting an appropriate construction setup, such as crew and equipment conformation, for a project. It is essential to choose a suitable method that can save time and avoid significant disruptions in the area, especially for projects in urban settings. Management must consider various resource (crew and equipment) combinations, calculate the associated time and construction productivity for each scenario, and determine the most desirable solution. In this research, a simulation-based approach was used to assist decision makers in choosing the best crew and equipment combination for lateral rehabilitation using cured-in-place pipe (CIPP) from the main line, also called lateral relining process using main and lateral cured-in-place liner (MLCIPL). The simulation model enables users to simulate for different resource compositions and calculate resource utilization and total duration of the project. The results’ comparison is demonstrated in this paper. This paper also suggests an amendment in the installation sequence to improve the construction productivity, which was developed from the results of this model.

Corrosion of underground pipelines is an important issue in the American pipeline industry. In 2002, the estimated annual cost was approximately US$7 billion for the monitoring, replacement, and maintenance of pipelines. Although significant improvements have occurred in corrosion engineering, the cost associated with the corrosion of buried pipes is still very high. According to current practices, physicochemical properties of subsoil, i.e., electrical resistivity, pH, redox potential, and sulfate and chloride concentrations, are widely used as indicators of the corrosive nature of soil. However, laboratory measurements of these parameters are often difficult due to time and budget constraints of projects. This paper evaluates the corrosion potential of subsoil using geotechnical properties. The study uses 15 specimens for the determination of geotechnical properties and electrical resistivity and the estimation of total sulfate and chloride content. The corrosion potential of the soil samples was evaluated from observed saturated minimum electrical resistivity and total sulfate and chloride content. The results indicate that the minimum saturated resistivity decreases and total sulfate and chloride content increases with the increase of liquid limits (LL), plasticity index (PI), activity, and cation exchange capacity (CEC). Therefore the corrosion potential of subsurface can be evaluated using geotechnical properties as a function of saturated minimum resistivity and total sulfate and chloride content. Furthermore, the pitting-type corrosion rate and decay in galvanized culvert pipe are estimated using electrical resistivity and are correlated with the geotechnical properties.

Construction of oil-and-gas pipeline networks is an important topic in the field of oil and gas development. The rationality and economy of pipeline-network construction are becoming increasingly important. Generally, the investment required for constructing pipeline networks is more than 30% of the total investment required for the development of an oil-gas field. Therefore, based on the characteristics of pipeline networks, the design of oil-gas pipeline networks needs to be optimized to reduce the investment. In this study, considering the discrete characteristic of facility location in the pipeline network, a comprehensive and optimal mathematical model of the star-tree oil-gas pipeline network was established considering various constraints. From the standpoint of characteristics of the complex model comprising numerous discrete variables, a hierarchical-optimization strategy was presented to decompose the optimization problem into four subproblems. An optimization program was compiled. Furthermore, the developed optimization program was applied to a case study to demonstrate the optimization process of the subproblem well clustering. Finally, the optimization program helped in optimizing the pipeline-network layout of a practical project under the known or unknown station location conditions. The manual and optimal designs were compared. Consequently, the optimization model presented in this paper was proven to be an effective method to solve the optimization problem for the star-tree oil-gas pipeline network in a discrete space.

By means of numerical modeling and experimental measurements, this work addresses the longstanding controversy of whether or not IR (ohmic) drops need to be considered in on-potential cathodic protection criteria. The results suggest that the IR drop is of little importance in many situations of practical relevance, and that its adverse influence on assessing the effectiveness of corrosion protection is generally overrated. This suggests that on-potentials are in principle suitable to be directly used for determining if a cathodic protection (CP) system offers adequate corrosion protection. This is considered a relevant finding because on-potentials are straightforward to measure, and their interpretation is free of many of the difficulties associated with instant-off potentials. Irrespective of the parameter used, however, a number of issues are discussed that need to be addressed in further work in order to provide the knowledge required to settle on threshold values.

Turkey is one of the most important countries in terms of natural gas consumption and transmission capacity. Turkey is an important transmission zone for international pipelines such as Baku–Ceyhan and Natural Gas Pipeline Project between Asia and Europe through Turkey (NABUCCO). This region also has very active and major fault lines. For this reason, the safety of natural gas networks and transmission pipelines subject to earthquake effects has become very important. In this paper, an area prone to earthquake-induced landslides in Istanbul has been studied to demonstrate the behavior of a natural gas pipeline network. This area is located near the North Anatolian Fault Zone (NAFZ), and an earthquake with a magnitude of approximately 7.5 is expected in Istanbul in the upcoming years. For this investigated region, seismic vulnerability of natural gas pipelines subject to permanent ground deformation and seismic-wave propagation effects have been investigated, and risks have been highlighted. Using elastic beam theory, a new approximation has been developed to calculate earthquake effects on buried continuous pipelines. Based on the new method, obtained results have been examined.

A research study was carried out recently in Ohio to evaluate the current method employed by Ohio Department of Transportation (ODOT) for load rating corrugated metal culverts installed under extremely shallow soil covers. In the study, six metal culvert structures were carefully selected, instrumented with sensors, and subjected to a series of static and dynamic live load tests. The field test data were analyzed to gain insight into how shallow-installation metal structures respond to live loading. The sensor readings were also used to compute thrust responses in the culverts. Then, the current ODOT load-rating procedure was applied to convert the live load to wall thrust. The thrust forces from the field tests and the calculations were compared. It was observed that the current ODOT procedure is very conservative, as the calculated thrust values were much higher than the field values for five of the six test structures.

Urban gas transmission and distribution system mainly consists of three subsystems: storage station, gas network, and users. The subsystem fault trees are established on the basis of the investigations of the subsystem faults and accidents. The probabilities of basic events of each subsystem fault tree are determined by combining expert judgment with fuzzy set theory, whereas the failure probabilities of top events and the importance analysis of basic events are evaluated by quantitative analysis. A fuzzy comprehensive evaluation approach is proposed for the risk assessment of urban gas transmission and distribution system, and is illustrated with a case study.

Lower-bound finite-element limit analysis in combination with nonlinear optimization was used to compute the lateral resistance of a pipeline buried in general cohesive-frictional soil. The failure load was presented in terms of nondimensional factors $F_c$ and $F_{\gamma }$ because of the components of soil cohesion and soil unit weight, respectively. The magnitudes of $F_c$ and $F_{\gamma }$ were found to be increasing with the increase in the value of the pipe embedment ratio and also with the increase of the internal friction angle of soil. Also, the failure patterns for different cases were examined.

This paper presents a fuzzy-based robustness measure and assessment of a buried pipeline for periods of 4, 8, 12, and 16 years. The adverse effects of corrosion on the performance of a buried steel pipeline are investigated based on the failure modes: deflection, wall thrust, buckling pressure, and bending strain. Other corrosion-induced failure modes such as blowout, splitting, and joint pullout are not considered in this paper but the proposed methodology can be used to assess any type of corrosion-related failures for steel, cast iron, and ductile iron pipes. To account for the amount and the damage of infrastructure due to corrosion is strenuous because of a lack of information and imprecise information associated with the corrosion process. Therefore, corrosion is considered as a fuzzy variable in the analyses so as to account for the intuitive feature of the corrosion-induced failure modes of buried pipelines. In this study, fuzzy-based entropy robustness is used, and it refers to a dimensionless measure that takes into account the uncertainty of the failure induced on buried pipes due to imprecise corrosion and associated uncertainty in structural response. The proposed approach gains its usefulness in the assessment by examining the robustness behavior of the structure at every membership level on different levels of imprecision. The effectiveness of the fuzzy entropy–based robustness measure on a buried pipeline has been demonstrated in this study. The outcome shows that the use of alpha-level discretization in the assessment of buried steel pipe based on fuzzy set and an entropy-based robustness measure approach would yield reliable results with an enhanced understanding of the impact of uncertainties and variabilities associated with pipe failure.