Concrete Cylinder Pipe Research Articles

Using Externally Bonded CFRP to Repair a PCCP with Broken Wires under Combined Loads

Prestressed concrete cylinder pipe (PCCP) is widely used for long-distance water pipelines throughout the world. However, prestressing wire breakage is the most common form of PCCP damage. For some pipelines that cannot be shut down, a new technique for in-service PCCP repair by externally bonding the pipe with layers of carbon fiber reinforced polymer (CFRP) was proposed. A set of three-dimensional finite element models of the repaired PCCP have been proposed and implemented in the ABAQUS software, which took into account the soil pressure, the weight of the PCCP, the weight of the water, and the hydrostatic pressure. The stress–strain features of the PCCP repaired with CFRP of various thicknesses were analyzed. The stress–strain features of different wire breakage rates for the repaired PCCP were also analyzed. The results showed that the strains and stresses decreased at the springline if the PCCP was repaired with CFRP, which improved the operation of the PCCP. It has been found that the wire breakage rates had a significant effect on the strains and stresses of each PCCP component, but CFRP failed to reach its potential tensile strength when other materials were broken.

Full-scale test and numerical simulation study on load-carrying capacity of prestressed concrete cylinder pipe (PCCP) with broken wires under internal water pressure

Damage-induced breaking of prestressed steel wires is one of the major causes of failure of prestressed concrete cylinder pipes (PCCPs). In this study, an internal pressure test of a full-scale PCCP model was conducted to measure the strain response of different layer structures of PCCP under internal working pressures with a broken wire percentage of 0% (intact), 5%, and 10% and to obtain the load response of the pipe with broken wires during the pressurization process. The test results showed that after the breaking of the prestressed wires, the prestress field was redistributed, caus ing cracks to first appear in the broken wire area. The strain of the concrete core in the broken wire area increased suddenly at the instant of wire breaking, generating circumferential microcracks, and the strain of unbroken wires on the side of the wire cut-off position increased as the number of broken wires increased. As the degree of wire breaking was increased, the degree of cracking at the broken wire section of the pipe significantly increased. When the percentage of broken wires reached 10%, longitudinal cracks occurred in the core concrete of the broken wire area, forming a weak zone in the pipe. A three-dimensional numerical model of a PCCP with broken wires was established based on the actual structural parameters of the test pipe and accounting for the bond stress of the protective mortar coating. The load-carrying capacities of PCCPs with broken wire percentages of 5%, 10%, 15%, 20%, and 25% were analyzed. Simulated and experimental results were compared, showing good agreement.

Experimental and numerical study on CFRP-lined prestressed concrete cylinder pipe under internal pressure

Prestressed concrete cylinder pipe (PCCP) has been widely used for water conveyance projects. However, prestressing wire breaks may result in the rupture of a pipe and cause a serious catastrophe. Application of carbon fiber reinforced polymer (CFRP) liners adhered to the inner concrete core is an effective method of internal repairing and strengthening of PCCP. In this study, a full-scale experimental test and corresponding finite element model evaluation were conducted to investigate the structural performance of CFRP-lined PCCP. In particular, the complex CFRP-concrete bonded interface was simulated by a cohesive element layer with a bilinear traction-separation response. In addition, the failure risk analysis method was introduced to determine the required number of CFRP layers for the distressed PCCP. The experimental results showed that the watertightness of liner can be improved by painting polyurea coating on the surface of CFRP laminate. It was shown by the simulation that for each additional layer of CFRP, the threshold value for the design pressure increases by 7 broken wires under the damage limit state and by 20 broken wires for the working pressure. The research presented in this paper can provide technical recommendations for the application of CFRP-lined PCCP and help utilities to better strengthen the distressed PCCP pipelines.

Low-coherent fiber-optic interferometry for in situ monitoring the corrosion-induced expansion of pre-stressed concrete cylinder pipes

The corrosion-induced expansion of pre-stressed concrete cylinder pipes shapes a major determining factor in the durability of most pipeline systems. However, a structure extended in a very large span and accompanied by a slow corrosion-induced structural damage is still a challenge in practice. Here, a low-coherent fiber-optic interferometry is proposed for in situ measuring the corrosion-induced expansion by directly circling the sensing optical fiber on the outer surface of the pipe. Since the accuracy of the absolute deformation measurement by the low-coherent fiber-optic interferometry can reach 3–5 μm, we are able to improve the sensitivity by choosing the length of the sensing fiber. In the experiment, we employ 50-m sensing fiber; therefore, a resolution of about 0.1 microstrains had been approached. We chose 12 places along the pipeline as the corrosion-induced expansion monitoring points. On monitoring for about half a year, a non-uniform interface in structure, such as the repaired places, was found as a key factor of the corrosion-induced expansion development, which could be a reference for the further health care of the pipeline structures.

Experimental Study on the Reinforcement of Prestressed Concrete Cylinder Pipes with External Prestressed Steel Strands

The prestressed concrete cylinder pipe (PCCP) suffers from cracks and degrades due to the prestress loss which is induced by wire breakage. Reinforcement with external prestressed strands is an option to return the deteriorating pipe’s ability to withstand internal pressures. This reinforcement contributes to actively compensating for the prestress loss caused by broken wires at an economic price. The crack propagation in the core is constrained by the strands. Moreover, the high tensile strength of strands does not decrease with an increase in the bending angle. It is also unnecessary to dewater the pipes during construction. To evaluate the reinforcement effect, a prototype test of a PCCP was performed in an assembled apparatus. The apparatus was mainly constituted by two PCCPs whose internal diameter is 2000 mm. The status of each component of the pipe was measured by resistance strain gauges in three sections along the axial direction at inverted (360°), crown (180°), and spring-line (90°, 270°) orientations. The maximum width of the cracks in the outer concrete core at spring-line reduced from 1.2 to 0.1 mm after strengthening. The cracks of the core concrete changed slightly when the internal water pressure increased to the design pressure of 0.9 MPa. The strengthened pipe was capable of sustaining the design internal water pressure and the water tightness property was in a good state. The strains of the steel strands were all below the tensile strain level. The reinforcement of the PCCP with external prestressed steel strands is able to meet the strengthen requirement of the test.

Rehabilitation Effect Evaluation of CFRP-Lined Prestressed Concrete Cylinder Pipe under Combined Loads Using Numerical Simulation

Prestressed concrete cylinder pipe (PCCP) has been widely used for water transfer and transit projects. However, prestressing wire breaks may result in the rupture of pipes and cause catastrophes. Carbon fiber reinforced polymer (CFRP) liners adhered to the inner concrete core can provide an effective method of internal repair and strengthening of PCCP. To evaluate the rehabilitation effect of CFRP-lined PCCP under combined loads, two contrasting three-dimensional finite element models that investigated the visual cracking of concrete and the yielding of steel cylinders were developed. A conceptual zone was introduced to analyze the different states of the pipe during the phase of wire break. In particular, the complex CFRP-concrete bonded interface was simulated by a cohesive element layer with a bilinear traction-separation response. The results show that CFRP has a good rehabilitation effect on the inner concrete core and steel cylinder but only a slight effect on the outer concrete core, prestressing wire, or mortar. A one-hoop CFRP layer diminishes the area of a yielding steel cylinder of 4.72 m2. In addition, CFRP works more effectively along with an increase in the number of broken wires. This research can provide a basis for strengthening distressed PCCP pipelines.

Experimental study on the structural behaviors of jacking prestressed concrete cylinder pipe

In this study, full-scale tests were conducted on Jacking Prestressed Concrete Cylinder Pipe (JPCCP) under external load, internal pressure, and combined load in order to evaluate its structural behaviors and possible failure modes. The experimental results indicate that external load plays a critical role in determining the onset of inner concrete core cracking at the invert and crown of a pipe. Once cracking appears in the inner concrete core of JPCCP under external load, the crack propagates rapidly and exhibits significant brittle fracture property. The onset of microcracking first appears in the exterior-reinforced concrete coating at the pipe springline in these three tests. Compared to the inner concrete core, cracks distributed in exterior-reinforced concrete coatings are smaller and narrower, as a result of the restriction imposed by the stirrup. The results of the combined load test show that JPCCP structure transforms from a perfect cycle into a damaged cycle, exhibiting a reduction in section stiffness at the pipe invert as loading increases. When the steel cylinder reaches its yield limit, the prestressing wire at the pipe invert yields soon after, and debonding (delamination) occurs between the steel cylinder and concrete almost simultaneously. Nevertheless, the JPCCP structure features excellent post-cracking capacity after a new equilibrium forms, and it exhibits enhanced ductile properties. Finally, a comparison between test results for JPCCP and Prestressed Concrete Cylinder Pipe (PCCP) is performed to illustrate the failure mode of JPCCP under combined load.

Research on Electromagnetic NDE Inspection Method for Broken Wire of PCCP

预应力钢筒混凝土管(Pre-stressed Concrete Cylinder Pipe, PCCP)作为一种新型的输水管材，被广泛应用于水利工程。在PCCP运行过程中，环境腐蚀或操作不当会导致管内高强钢丝的腐蚀或断裂，进而导致泄漏、爆管等事故。目前国内外普遍采用电磁涡流检测技术，对PCCP的断丝与金属管壁健康状态进行无损检测，检测系统在管内运行并配合计程轮等工具实现断丝位置的定位。本文针对国内外两种常用的PCCP断丝电磁检测技术，即远场涡流检测方法和正交电磁检测方法，建立了简化分析模型，并给出了等效交流电路，通过仿真分析验证了模型的正确性。分析了电磁检测频率的选取原则，建议选取23 Hz作为检测频率。给出了电磁检测系统的设计与实现，并经过了管道断丝试验验证，有效提取了故障特征。 Pre-stressed Concrete Cylinder Pipe (PCCP), as a new type of pipeline for water delivery, has been widely used in water conservancy projects. During the operation of PCCP, environmental corrosion or improper operation will lead to corrosion or fracture of high-strength steel wire in the pipe, resulting in leakage, explosion and other accidents. Currently some nondestructive methods, such as electromagnetic eddy current inspection method, are widely used to test the broken wire and assess the health PCCP, and equipped with a counting-wheel or other tools to achieve the localization of broken wires. This paper presents a simple model of two famous electromagnetic detection technologies for PCCP broken wire, i.e. the remote field eddy current testing method and orthogonal electromagnetic detection method. Also the equivalent AC circuit is given. By simulation analysis the simple model is verified. The selection principle of electromagnetic detection frequency is analyzed, and 23 Hz is selected as the detection frequency. The design and implementation of the electromagnetic detection system are given, and the fault characteristics are effectively extracted through the broken wire tests.

Experimental Assessment of The 100 mV Polarization Shift Criterion for Cathodic Protection Systems of the Prestressed Concrete Cylinder pipes

In this work, an experimental study was carried out to evaluate the 100 mV polarization shift criterion for confirming the effectiveness of applied cathodic protection viz via zinc sacrificial anodes to arrest progress of corrosion in uncorroded or partially corroded high tensile grade prestressing steel wires of the same grade as the one used to manufacture the prestressed concrete cylinder pipes (PCCP). Total number of 14 wire samples were placed under constant tension approximately 55% of their ultimate tensile strength by the use of specially designed and fabricated holding metal frames. All samples were individually immersed in glass vessels filled with alkaline solutions of pH around 12 and variable chloride ions concentration ranging from 500 to 3000 ppm. With the exception of one wire sample left unprotected; the remaining samples were cathodically protectedby systems of zinc sacrificial anodes such that an average measured polarization shift near 100 mV with variable chloride content in solution was maintained for 9 samples and near 75, 50, and 25 mV with constant chloride content of 3000 ppm. Evaluation of mechanical properties of wire samples suggested that 100 mV criterionand more than sufficient to confirm the adequacy and effectiveness of zinc sacrificial anodes cathodic protection system to arrest progress of corrosion of partially corroded and uncorroded prestressing steel wires in alkaline passivating environment contaminated with chloride ions up to 3000 ppm in solution and for shifts in polarization as low as 25 mV. It was also evident that corrosion progress in the prestressing steel wires can not be arrested in the 3000 ppm chloride environment without the application of cathodic protection.

Surface Crack Detection in Prestressed Concrete Cylinder Pipes Using BOTDA Strain Sensors

Structural deterioration after a period of service can induce the failure of prestressed concrete cylinder pipes (PCCPs), with microcracks in the coating leading to the corrosion of the prestressed wires. In this paper, we propose the use of Brillouin optical time-domain analysis (BOTDA) strain sensors for detecting the onset of microcracking in PCCP coating: the BOTDA strain sensors are mounted on the surface of the PCCP, and distributed strain measurements are employed to assess the cracks in the mortar coating and the structural state of the pipe. To validate the feasibility of the proposed approach, experimental investigations were conducted on a prototype PCCP segment, wherein the inner pressure was gradually increased to 1.6 MPa. Two types of BOTDA strain sensors—the steel wire packaged fiber optic sensor and the polyelastic packaged fiber optic sensor—were employed in the experiments. The experimental distributed measurements agreed well with the finite element computations, evidencing that the investigated strain sensors are sensitive to localized deterioration behaviors such as PCCP microcracking.

IN-SITU TEST EXPERIMENTAL RESEARCH ON LEAKAGE OF LARGE DIAMETER PRE-STRESSED CONCRETE CYLINDER PIPE (PCCP)

In recent years, a big number of large diameter pre-stressed concrete cylinder pipe (PCCP) lines have been applied to the Mid-route of the South-to-North Water Transfer Project. However, the leakage problem of PCCP causes annually heavy economic losses to our country. In such a context of situation, how to detect leaks rapidly and precisely after pipes appear cracks in water supply system has great significance. Based on the study and analysis of the characteristic structure of large diameter PCCP, a new leak detection system using fiber Bragg grating sensors, which can capture signals of water pressure change, is proposed. The feasibility, reliability and practicability of the system could be acceptable according to data achieved from in–situ tests. Moreover, the leak detection system can monitor in real-time of dynamic change of water pressure. The equations of the leakage quantity and water pressure have been presented in this paper, which can provide technical guidelines for large diameter PCCP lines maintenance.

Failure Analysis of a Water Supply Pumping Pipeline System

This paper describes the most important results of a theoretical, experimental and in situ investigation developed in connection with a water supply pumping pipeline failure. This incident occurred after power failure of the pumping system that caused the burst of a prestressed concrete cylinder pipe (PCCP). Subsequently, numerous hydraulic transient simulations for different scenarios and various air pockets combinations were carried out in order to fully validate the diagnostic. As a result, it was determined that small air pocket volumes located along the pipeline profile were recognized as the direct cause of the PCCP rupture. Further, a detail survey of the pipeline was performed using a combination of non-destructive technologies in order to determine if immediate intervention was required to replace PCC pipes. In addition, a hydraulic model was employed to analyze the behavior of air pockets located at high points of the pipeline.

Comparison of carbon footprints of steel versus concrete pipelines for water transmission

ABSTRACTThe global demand for water transmission and service pipelines is expected to more than double between 2012 and 2022. This study compared the carbon footprint of the two most common materials used for large-diameter water transmission pipelines, steel pipe (SP) and prestressed concrete cylinder pipe (PCCP). A planned water transmission pipeline in Texas was used as a case study. Four life-cycle phases for each material were considered: material production and pipeline fabrication, pipe transportation to the job site, pipe installation in the trench, and operation of the pipeline. In each phase, the energy consumed and the CO2-equivalent emissions were quantified. It was found that pipe manufacturing consumed a large amount of energy, and thus contributed more than 90% of life cycle carbon emissions for both kinds of pipe. Steel pipe had 64% larger CO2-eq emissions from manufacturing compared to PCCP. For the transportation phase, PCCP consumed more fuel due to its heavy weight, and therefore had larger CO2-eq emissions. Fuel consumption by construction equipment for installation of pipe was found to be similar for steel pipe and PCCP. Overall, steel had a 32% larger footprint due to greater energy used during manufacturing.Implications: This study compared the carbon footprint of two large-diameter water transmission pipeline materials, steel and prestressed concrete cylinder, considering four life-cycle phases for each. The study provides information that project managers can incorporate into their decision-making process concerning pipeline materials. It also provides information concerning the most important phases of the pipeline life cycle to target for emission reductions.

Effect of the Number of Broken Wire Wraps on the Structural Performance of PCCP with Full Interaction at the Gasket Joint

AbstractBroken prestressing wire wraps are the main cause of failure in prestressed concrete cylinder pipes (PCCP). The effect of the number and location of broken wire wraps on the structural performance of PCCP is investigated using advanced numerical modeling that considers full interaction between the spigot and bell ends of adjacent pipes. The stresses and strains in the various components of PCCP are evaluated with increasing internal pressure. A sensitivity analysis is performed to understand how manipulating the severity of the damage through varying the number of broken wire wraps affects the internal fluid pressure that causes failure. A 244-cm (96-in.) embedded cylinder pipe (ECP) is modeled with 5, 35, 70, and 100 broken wire wraps. The results obtained show that the internal fluid pressure required to cause failure can be as much as 14% lower when the damage is at the joint, and that the internal pressure that causes yielding of the wire wraps decreases approximately 65% as the severity of th...

Online monitoring of wire breaks in prestressed concrete cylinder pipe utilising fibre Bragg grating sensors

With steel prestressing wires tensioned around core, Prestressed Concrete Cylinder Pipe (PCCP) is a high-strength composite pipe designed for large-diameter water propagation and distribution. However, some PCCPs may fail after a certain time of service due to corrosion and deterioration. Real-time health monitoring of wire breaks is essential to assess the condition and avoid catastrophic failures of PCCPs. In this paper, a novel approach based on Fibre Bragg Grating (FBG) sensing technology, is presented to monitor and locate wire breaks in PCCP lines. FBG vibration sensors are utilised to capture the signals of wire break activities in the pipeline and obtain their locations. The online monitoring system and localization principle of wire break activities are described. Preliminary experiments were carried out on PCCPs with an inner diameter of 2m, which were filled with pressurized water. Experimental results indicate that the wire break activity can be detected and located effectively by FBG sensors. The detection error of wire break locations is analysed. With unique features, the proposed non-destructive method is expected to be used for the online monitoring of wire break activities in long term for the condition assessment and performance prediction of PCCP lines.

Structural performance of buried prestressed concrete cylinder pipes with harnessed joints interaction using numerical modeling

Broken prestressing wire wraps are the main cause of failure in buried prestressed concrete cylinder pipes (PCCP), which form the backbone of water and wastewater infrastructure networks in North America. Advanced numerical modeling using non-linear finite elements is used to model the effect of the number and location of broken wire wraps on the structural performance of Class 125-14, 96-in. PCCP. The modeling technique used is unique in that it considers full interaction between adjacent pipes with harnessed joints, as well as combined internal and external loading with full soil–pipe interaction. Performance indicators in the various components of PCCP are monitored as internal pressure is increased. A sensitivity analysis is presented for how manipulating the severity of the damage affects the failure pressure of the pipe. The results show that the internal fluid pressure required to cause failure can be as much as 34% lower when the damage is at the barrel of the pipe, and that the internal pressure that causes yielding of the wire wraps decreases by 66% as the damage worsens from 5 to 100 wire breaks.

Effect of RuCl3Concentration on the Lifespan of Insoluble Anode for Cathodic Protection on PCCP

Prestressed Concrete steel Cylinder Pipe (PCCP) is extensively used as seawater pipes for cooling in nuclear power plants. The internal surface of PCCP is exposed to seawater, while the external surface is in direct contact with underground soil. Therefore, materials and strategies that would reduce the corrosion of its cylindrical steel body and external steel wiring need to be employed. To prevent against the failure of PCCP, operators provided a cathodic protection to the pre-stressing wires. The efficiency of cathodic protection is governed by the anodic performance of the system. A mixed metal oxide (MMO) electrode was developed to meet criteria of low over potential and high corrosion resistance. Increasing coating cycles improved the performance of the anode, but cycling should be minimized due to high materials cost. In this work, the effects of RuCl3 concentration on the electrochemical properties and lifespan of MMO anode were evaluated. With increasing concentration of RuCl3, the oxygen evolution potential lowered and polarization resistance were also reduced but demonstrated an increase in passive current density and oxygen evolution current density. To improve the electrochemical properties of the MMO anode, RuCl3 concentration was increased. As a result, the number of required coating cycles were reduced substantially and the MMO anode achieved an excellent lifespan of over 80 years. Thus, we concluded that the relationship between RuCl3 concentration and coating cycles can be summarized as follows: No. of coating cycle = 0.48*[RuCl3 concentration, M] -0.97 .

PCCP Rehabilitation: Optimizing System Performance and Leveraging Drought Management Opportunities

Motivated by high long‐term projected costs of reactively repairing prestressed concrete cylinder pipe (PCCP) and in the midst of a severe drought, the Metropolitan Water District of Southern California has developed an extensive PCCP, proactive rehabilitation program with benefits that include cost savings, risk mitigation, and improved operations.

Effect of Mortar Coating’s Bond Quality on the Structural Integrity of Prestressed Concrete Cylinder Pipe with Broken Wires

In North America, 90 out of 100 large water utilities utilize Prestressed Concrete Cylinder Pipe (PCCP) in their water transmission mains or force mains since 1942. This is mainly due to its low cost and relatively stable performance compared with other large-diameter pipe materials working under high-pressure. Though PCCP has relatively low failure rate, its failures usually occur without warning and can cause catastrophic consequences, threatening public safety. Most PCCP failures are caused by the breakage of prestressing wires that hold the pipe in compression. To be proactive and avoid PCCP failures, it is important to know the pipe condition and then take actions before it fails. Hence, numerical models have been developed to evaluate the pipe condition. However, current numerical models do not consider the bond between the presressing wires and mortar coating. Instead all broken wires are removed in the model. This is over-conservative and many good pipes had been misjudged to be “bad” pipes, causing unnecessary and very costly pipe excavation and replacement. To effectively and efficiently manage PCCP pipeline, it is very important to have a realistic modeling of the broken prestressing wires by considering the bond quality of the mortar coating. This paper analyzes the effect of mortar coating’s bond quality on PCCP’s structural integrity. A theoretical approach is proposed to determine the length of broken wires losing prestress by considering the bond quality of the mortar coating. Based on the proposed method, a numerical model is developed and the pipe’s structural integrity is analyzed. Several cases with different bond qualities of mortar coatings are analyzed in this paper. The results are then compared and summarized. The simulations results indicate that PCCPs with good mortar bond are not compromised much, while the assumptions of current models are too conservative. The research presented in this paper provides a better understanding of the importance of considering bond quality in modeling PCCP. The findings of this research can help utilities better management their PCCP pipelines with different bond qualities.

Effect of the location of broken wire wraps on the failure pressure of prestressed concrete cylinder pipes

AbstractThe effect of the location of broken prestressing wire wraps on the overall strength of prestressed concrete cylinder pipes (PCCP) is investigated here. An advanced computational model based on non‐linear finite element analysis is used to study three possible locations of broken wire wraps: at the spigot joint, at the bell joint and in the barrel of the pipe. A sensitivity analysis was performed to evaluate the cracking of the concrete core and the yielding of the prestressing wires and steel cylinder with increasing internal pressure and with an increasing number of broken wire wraps. Two classes of 2.44 m embedded cylinder pipe (ECP) were modelled with 5, 35, 70, and 100 wire wrap breaks. The results show that broken wire wraps at the joint, and especially the spigot joint, decrease the overall strength of PCCP more so than those at the bell joint or in the barrel of the pipe. The intensity of this effect increases with increasing internal pressure and with a larger number of broken wire wraps.