This document discusses stress modeling of pipelines strengthened with advanced composite materials. It begins by introducing the need to rehabilitate pipelines damaged by environmental factors and corrosion. Fiber reinforced polymer composites are presented as a potential new method for pipeline repair without excavation. Theoretical stress models are developed to analyze the effects of internal pressure, soil loading, and composite reinforcement on the circumferential stresses in the pipe wall. Equations are provided to calculate hoop stresses from internal pressure and bending stresses from soil loading on undamaged pipes.
Eigenvalue Buckling Computation and Impact on Pipeline Wall Thickness and Sub...IOSRJMCE
Submarine pipelines used in the transportation of hydrocarbon in the oil and gas industry are usually subjected to external hydrostatic pressure and compressive stresses resulting in susceptibility to buckling and loss of structural stability. The objective of the present work was to examine influence of wall thickness on eigenvalue buckling load and hydrostatic pressure on ocean depth. Linear buckling analysis was conducted employing finite element method using ANSYS software package and the simulation was conducted varying wall thickness and ocean depth. The investigation showed collapse buckling pressure decreased linearly with ocean water depth but increased with thickness increment. Pipeline buckling failure can be minimized with wall thickness optimization design and selection.
This document describes a 3D numerical model that was developed to simulate the deformation of a glass reinforced plastic (GRP) pipe during a pipejacking process. The model was created using ANSYS finite element software and was validated by comparing the modeled longitudinal strain patterns to strain data measured from fiber optic sensors installed on a GRP pipe that was jacked as part of a sewer project in Australia. Key factors that were found to influence the pipe's deformation included the eccentricity of jacking forces, the impact of a loading body surrounding the pipe, and the pipe's material properties. The validated model can help improve pipejacking design by allowing for higher jacking forces and shorter construction times with lower safety factors.
Auber_Steel fiber reinforcement concrete_Slab on ground-Design NoteHoa Nguyen
This document provides design guidelines for slabs on ground using Auber steel fiber concrete. It discusses general principles of yield line design theory and describes procedures for determining the load carrying capacity of slabs. Material properties for Auber steel fibers are specified based on testing standards. The design process involves discretizing the slab cross-section into layers and determining fiber distribution. Load cases include uniform and point loads. Models are presented for analyzing the effects of temperature, shrinkage, and different load configurations. Critical aspects like shear capacity and punching are also addressed.
This document discusses the development of an ultra-high pressure riser system using a shrink-fit connection method for deep water drilling. Key points:
1) Shrink-fitting was developed as an alternative to welding for joining thick-walled, high strength steel pipes needed to withstand internal pressures up to 15,000 psi.
2) Testing of small-scale and half-scale prototypes validated the shrink-fit connection's ability to seal and withstand extreme tension and pressure loads well beyond operating conditions.
3) Finite element analysis showed the shrink-fit connection has better fatigue resistance than welded joints, with an axial stress concentration factor below 1.
State-of-the-art review of FRP strengthened RC slabsIJSRD
1) The document reviews different techniques for strengthening reinforced concrete slabs using fibre reinforced polymers (FRP), including externally bonded reinforcement and near surface mounted reinforcement.
2) It summarizes the advantages of FRP including corrosion resistance, ease of installation, and simplicity, and discusses how FRP can be used to strengthen beams, columns, and slabs.
3) The literature review found that FRP is effective at increasing load capacity of slabs with openings when used to strengthen, though debonding is a risk, and other techniques like steel plates can provide some strengthening but are limited.
This document summarizes research on post-tensioning in buildings. It details the history of post-tensioning from its origins in the 1940s-1950s to its use in the first high-rise building with post-tensioned slabs in 1956. The document then discusses the benefits of post-tensioned slabs and methodology used in the research, including monitoring a construction site. Test results are presented analyzing properties of post-tensioned concrete mixes. The research concludes that post-tensioned slabs provide construction speed and cost benefits compared to reinforced concrete.
1) The document analyzes stress on buried pipelines using CAESAR II software. A pipeline system is modeled and different load cases are applied including operating, sustained, and expansion loads.
2) Stress results like axial stress, bending stress, torsion stress and hoop stress are obtained from the software. The maximum stress is below the allowable stress specified in the ASME B31.1 code.
3) Finite element analysis is also carried out using ABAQUS to model the soil-pipeline interaction. The maximum stress is found at the top and bottom of the pipeline due to vertical static loads.
A REVIEW ON STRENGTHENING OF REINFORCED CONCRETE BEAMS USING GLASS FIBER REIN...Ijripublishers Ijri
Worldwide, a great deal of research is currently being conducted concerning the use of fiber reinforced plastic wraps,
laminates and sheets in the repair and strengthening of reinforced concrete members. Fiber-reinforced polymer (FRP)
application is a very effective way to repair and strengthen structures that have become structurally weak over their life
span. FRP repair systems provide an economically viable alternative to traditional repair systems and materials.
Experimental investigations on the flexural and shear behavior of RC beams strengthened using continuous glass fiber
reinforced polymer (GFRP) sheets are carried out. Externally reinforced concrete beams with epoxy-bonded GFRP sheets
were tested to failure using a symmetrical two point concentrated static loading system. Two sets of beams were casted
for this experimental test program. In SET I three beams weak in flexure were casted, out of which one is controlled
beam and other two beams were strengthened using continuous glass fiber reinforced polymer (GFRP) sheets in flexure.
In SET II three beams weak in shear were casted, out of which one is the controlled beam and other two beams were
strengthened using continuous glass fiber reinforced polymer (GFRP) sheets in shear. The strengthening of the beams
is done with different amount and configuration of GFRP sheets.
Eigenvalue Buckling Computation and Impact on Pipeline Wall Thickness and Sub...IOSRJMCE
Submarine pipelines used in the transportation of hydrocarbon in the oil and gas industry are usually subjected to external hydrostatic pressure and compressive stresses resulting in susceptibility to buckling and loss of structural stability. The objective of the present work was to examine influence of wall thickness on eigenvalue buckling load and hydrostatic pressure on ocean depth. Linear buckling analysis was conducted employing finite element method using ANSYS software package and the simulation was conducted varying wall thickness and ocean depth. The investigation showed collapse buckling pressure decreased linearly with ocean water depth but increased with thickness increment. Pipeline buckling failure can be minimized with wall thickness optimization design and selection.
This document describes a 3D numerical model that was developed to simulate the deformation of a glass reinforced plastic (GRP) pipe during a pipejacking process. The model was created using ANSYS finite element software and was validated by comparing the modeled longitudinal strain patterns to strain data measured from fiber optic sensors installed on a GRP pipe that was jacked as part of a sewer project in Australia. Key factors that were found to influence the pipe's deformation included the eccentricity of jacking forces, the impact of a loading body surrounding the pipe, and the pipe's material properties. The validated model can help improve pipejacking design by allowing for higher jacking forces and shorter construction times with lower safety factors.
Auber_Steel fiber reinforcement concrete_Slab on ground-Design NoteHoa Nguyen
This document provides design guidelines for slabs on ground using Auber steel fiber concrete. It discusses general principles of yield line design theory and describes procedures for determining the load carrying capacity of slabs. Material properties for Auber steel fibers are specified based on testing standards. The design process involves discretizing the slab cross-section into layers and determining fiber distribution. Load cases include uniform and point loads. Models are presented for analyzing the effects of temperature, shrinkage, and different load configurations. Critical aspects like shear capacity and punching are also addressed.
This document discusses the development of an ultra-high pressure riser system using a shrink-fit connection method for deep water drilling. Key points:
1) Shrink-fitting was developed as an alternative to welding for joining thick-walled, high strength steel pipes needed to withstand internal pressures up to 15,000 psi.
2) Testing of small-scale and half-scale prototypes validated the shrink-fit connection's ability to seal and withstand extreme tension and pressure loads well beyond operating conditions.
3) Finite element analysis showed the shrink-fit connection has better fatigue resistance than welded joints, with an axial stress concentration factor below 1.
State-of-the-art review of FRP strengthened RC slabsIJSRD
1) The document reviews different techniques for strengthening reinforced concrete slabs using fibre reinforced polymers (FRP), including externally bonded reinforcement and near surface mounted reinforcement.
2) It summarizes the advantages of FRP including corrosion resistance, ease of installation, and simplicity, and discusses how FRP can be used to strengthen beams, columns, and slabs.
3) The literature review found that FRP is effective at increasing load capacity of slabs with openings when used to strengthen, though debonding is a risk, and other techniques like steel plates can provide some strengthening but are limited.
This document summarizes research on post-tensioning in buildings. It details the history of post-tensioning from its origins in the 1940s-1950s to its use in the first high-rise building with post-tensioned slabs in 1956. The document then discusses the benefits of post-tensioned slabs and methodology used in the research, including monitoring a construction site. Test results are presented analyzing properties of post-tensioned concrete mixes. The research concludes that post-tensioned slabs provide construction speed and cost benefits compared to reinforced concrete.
1) The document analyzes stress on buried pipelines using CAESAR II software. A pipeline system is modeled and different load cases are applied including operating, sustained, and expansion loads.
2) Stress results like axial stress, bending stress, torsion stress and hoop stress are obtained from the software. The maximum stress is below the allowable stress specified in the ASME B31.1 code.
3) Finite element analysis is also carried out using ABAQUS to model the soil-pipeline interaction. The maximum stress is found at the top and bottom of the pipeline due to vertical static loads.
A REVIEW ON STRENGTHENING OF REINFORCED CONCRETE BEAMS USING GLASS FIBER REIN...Ijripublishers Ijri
Worldwide, a great deal of research is currently being conducted concerning the use of fiber reinforced plastic wraps,
laminates and sheets in the repair and strengthening of reinforced concrete members. Fiber-reinforced polymer (FRP)
application is a very effective way to repair and strengthen structures that have become structurally weak over their life
span. FRP repair systems provide an economically viable alternative to traditional repair systems and materials.
Experimental investigations on the flexural and shear behavior of RC beams strengthened using continuous glass fiber
reinforced polymer (GFRP) sheets are carried out. Externally reinforced concrete beams with epoxy-bonded GFRP sheets
were tested to failure using a symmetrical two point concentrated static loading system. Two sets of beams were casted
for this experimental test program. In SET I three beams weak in flexure were casted, out of which one is controlled
beam and other two beams were strengthened using continuous glass fiber reinforced polymer (GFRP) sheets in flexure.
In SET II three beams weak in shear were casted, out of which one is the controlled beam and other two beams were
strengthened using continuous glass fiber reinforced polymer (GFRP) sheets in shear. The strengthening of the beams
is done with different amount and configuration of GFRP sheets.
This document summarizes a study on rehabilitation techniques for existing concrete structures. It discusses various repair methods and materials that can be used, including polymer modified mortar. Non-destructive tests were conducted on a sample structure to evaluate its condition. Based on the results, polymer modified mortar was selected for repairing columns due to its low cost, ease of application, and ability to extend the life of the building for 15-18 years at a lower cost than reconstruction. The study concludes that repairing existing structures using appropriate technologies and materials is more economical than demolition and aims to provide guidance on cost-effective rehabilitation.
Influence of Local Effects on Hold Period Fatigue Assessments for Reel-LayPaul Brett
Local effects at the hang-off clamp (HOC) where a pipeline is held during offshore installation can influence fatigue damage assessments. Finite element analysis found that local frictional slip and insulation compliance reduce the stress concentration factor compared to assuming full fixity. This lower stiffness and added damping were incorporated into dynamic simulations, finding lower predicted fatigue damage than with full fixity. Accounting for local HOC effects more accurately represents pipeline behavior and could allow longer hold periods.
This document proposes an alternative design for constructing the foundations of a new pedestrian bridge across a harbour. It suggests using a temporary sheet pile wall cofferdam that would allow workers to build the pile group and pile cap at the riverbed level, avoiding the need for divers. The cofferdam design is sized at 10x10m and embedded 10m deep. Calculations are presented to check for piping, heaving, and structural failure. A finite element model is also used. It is determined that drains will be needed to reduce water pressures and piping risks. The design of the internal bracing structure and construction sequence are also considered. The cofferdam is concluded to be a feasible alternative construction method for the bridge
This document provides an overview of a book containing 200 questions and answers on practical civil engineering works. The book is intended to arouse interest in graduate engineers, assistant engineers, and engineers regarding technical aspects of civil engineering projects. It covers topics like bridge works, concrete structures, drainage works, earthworks, piers/marine structures, roadworks, pumping stations, reclamation works, water retaining structures, pipe jacking/microtunneling, piles/foundations, and general civil engineering questions. The author's goal is to explain the reasoning behind common engineering practices to help readers better understand the underlying principles.
200 Questions and Answers on Practical Civil Engineering Works [2]_2008.pdfMasi Uddin
This document contains a preface and 12 chapters related to practical questions and answers on various aspects of civil engineering works. The preface states that the book aims to provide graduate engineers and practicing engineers with technical knowledge on current civil engineering practices. It contains over 200 questions and answers selected from the author's monthly journal column on civil engineering topics. The chapters cover various topics related to bridge works, concrete structures, drainage works, earthworks, marine structures, roadworks, pumping stations, reclamation works, water retaining structures, pile foundations, and general civil engineering questions.
Construction of modern buildings requires many pipes and ducts in order to accommodate essential services such as air conditioning, electricity, telephone, and computer network. Web openings in concrete beams enable the installation of these services. A number of studies have been conducted with regards to reinforced concrete beams which contain web openings. The present paper aims to compile this state of the art work on the type of Reinforced Concrete (RC) beams with transverse web openings. Various design approaches and strengthening techniques are also presented.
IRJET- Study on Causes of Cracks and its Remedial Measures in Reinforced Conc...IRJET Journal
The document discusses cracks in reinforced concrete bridge piers and abutments. It first provides background on the causes of cracking, including applied loads, restraint from volume changes, and drying shrinkage. It then presents a case study of a bridge exhibiting cracks in the abutments and approaches. The cracks are thought to be caused by movement of the abutments due to issues with surrounding soils. The document outlines various remedial measures that could address abutment movement and cracking, such as soil grouting, concrete jacketing, and epoxy injection. It concludes that abutment movement must be addressed to prevent further deterioration of the bridge structure.
Flexible thermoplastic culverts like Enviro-Span can withstand much deeper fill depths than rigid materials like steel or concrete due to soil arching effects. Finite element analysis shows Enviro-Span can safely withstand at least 115 feet of fill, which is orders of magnitude more than comparable steel arches. Research also indicates standards like AASHTO are overly conservative, and a 5-foot HDPE pipe can safely withstand over 80 feet of fill. As a thermoplastic, Enviro-Span interacts with soil to form a composite structure that distributes loads more efficiently than rigid materials, allowing it to withstand extremely deep fill depths.
The document discusses stresses around underground openings such as tunnels. It describes how underground openings alter the initial stress state of rocks and how determining stresses is important for design. Different types of tunnels and excavation methods are also outlined. The document then focuses on analyzing stresses around circular underground openings using transformations between rectangular and polar coordinate systems. It presents solutions for circular openings under hydrostatic stress fields and discusses elastic-plastic behavior, including Bray's model for analyzing squeezing tunnels.
This document evaluates utilizing commercially available PVC tubes as compression members filled with concrete. An experimental study tested 4 concrete-filled PVC columns and 2 plain concrete columns as references. The concrete-filled PVC columns exhibited higher strength and ductility than the plain concrete columns. Testing showed that the PVC tubes increased the compressive strength of the concrete core by confining it and allowing for larger lateral deformation before failure. The PVC tubes contained the shear failure of the concrete core at an angle of approximately 45 degrees. The study provides a basis for further research on concrete-filled PVC tubes with varying dimensions and concrete properties.
IRJET- Behavior of Compound Concrete Filled Reinforced PVC Tubes Under Compre...IRJET Journal
This document discusses an experimental study on the compressive behavior of compound concrete filled reinforced polyvinyl chloride (PVC) tubes compared to unreinforced PVC tubes. Compound concrete contains a mixture of fresh concrete and demolished concrete lumps. Ten specimens were tested - two unreinforced and eight with internal steel stirrup reinforcement at varying spacings. Results showed that reinforced specimens had higher load capacity and compressive strength than unreinforced specimens. Closer stirrup spacing led to higher strength. Reinforcement improved the compressive performance of the composite tubes.
Ground improvement technic and repair procedures.pdfKumarS250747
Foundation Design requires the knowledge of the behavior of the structure supported by the foundation as well as that of soil or rock that furnishes the ultimate support.
The super structure, foundation and soil or rock must act together and each must posses its unique serviceability and safety in the interactive system
The soil or rock may provide adequate safety of the foundation against failure, detrimental settlement may occur prior to any collapse. Which may be analogous to beam or truss in super structure but does not meet the serviceability(Deflection) criteria
The super structure designs are controlled by the strength of material such as shear strength ,compressive strength and tensile strength but deformations governs the design of foundation.
This document summarizes chapter 4 of the book "Structural Concrete Design" which covers various topics related to designing structural concrete including:
- Properties of concrete and reinforcing steel such as compressive strength, modulus of elasticity, creep, and tensile strength.
- Proportioning and mixing concrete, including using admixtures.
- Flexural and strength design of beams, slabs, columns, shear/torsion, development of reinforcement, two-way systems, frames, brackets/corbels, and footings.
- Additional concrete types such as lightweight and high-strength concrete.
This document provides an overview of subsea pipeline systems. It discusses the key components including wellhead platforms, risers, pipelines, manifolds, and flowlines. It then describes various types of subsea pipelines and their purposes for transporting hydrocarbons from offshore production units to shore. The rest of the document outlines the major design considerations and analyses performed for subsea pipelines, such as sizing, material selection, mechanical design, stability, crossings, and cathodic protection. Standards and codes used for subsea pipeline design are also listed.
Effect Of Water On Slope Stability And Investigation Of ΝΝw Drainage Techniqu...IJMER
This document summarizes a study on using drainage gravel piles to stabilize landslides along sections of the Egnatia Odos highway in Greece. Drainage gravel piles are vertical wells filled with permeable gravel that act as drains to lower the water table and pore water pressure within landslide-prone areas. The study investigates applying this technique to a landslide zone along the highway underlain by a buried river terrace with high permeability. It describes the geology and groundwater conditions contributing to landslides. Calculations are presented on the expected drawdown cone and impact radius of drainage gravel piles based on pumping test principles. The construction method is outlined. The study concludes drainage gravel piles can effectively drain landslide materials by channeling
1. The document discusses parameters that affect the strength of concrete in externally prestressed bridges. It examines factors like tendon layout, prestressing method, effective depth and eccentricity of external tendons, and materials used for tendons.
2. Studies have found that draped tendon profiles provide higher strength than straight profiles. External prestressing requires more prestressing force than internal prestressing, except for very deep girders. Increased effective depth and eccentricity of external tendons enhances strength.
3. Carbon fiber reinforced polymer tendons are an alternative to steel but have issues with brittleness and cost. Overall, optimizing tendon layout and placement can improve the strength of externally prestressed concrete bridges
Comparative Study on the Design of Square,Rectangular and Circular Concrete W...IJERA Editor
Reinforced concrete overhead water tanks are used to store and supply safe drinking water. Design and cost estimation of overhead water tanks is a time consuming task, which requires a great deal of expertise. This study therefore examines the efficiency of Rectangular and Circular tanks. Tanks of 30m3, 90m3, 140m3 and 170m3 capacities were used in order to draw reasonable inferences on tank‟s shape design effectiveness, relative cost implications of tank types and structural capacities. Limit state design criteria were used for basic tank‟s construction materials- steel reinforcement, concrete and formwork were taken-off from the prepared structural drawings. Results of the material take-offs showed that, for each of the shapes, the amount of each structural materials increase as the tank capacity increases. Also Circular-shaped tank consumed lesser individual material as compared to Rectangular ones. Hence, this will give Circular-shaped tanks a more favoured selection over the rectangular shaped tanks.
Prestressed concrete uses tensioned steel to put concrete in compression and improve its performance. Circular structures like pipes, tanks and poles are well-suited for circular prestressing using hoop tension to counteract internal fluid pressure. Pipes can be made through monolithic, two-stage or precast construction. Design considerations include stresses from handling, support conditions, working pressure and cracking. Tanks come in different shapes and are analyzed as shells. Poles are designed for various loads as vertical cantilevers with tapering cross-sections.
This document discusses the various loads that act on concrete dams, including primary, secondary, and exceptional loads. It provides details on the following primary loads: water load, self-weight load, and seepage loads (internal and external uplift). Secondary loads discussed include sediment load, wave load, wind load, and ice load. Exceptional loads mentioned include seismic and tectonic effects. The document also contains schematic diagrams that illustrate how these loads are distributed on gravity dams and their points of application. Equations are provided for calculating the magnitudes of several load types.
Seismic response of steel beams coupling concrete wallsYahya Ali
The document summarizes an experimental study on the seismic response of steel link beams coupling reinforced concrete walls. Two specimen walls were tested with short span steel beams connecting the walls. The steel beams were designed according to seismic standards to yield in shear and dissipate energy through hysteretic damping. Both specimen walls exhibited excellent ductility and energy absorption. The steel beams remained elastic with minor local buckling. The study demonstrated that steel link beams can provide ductile connections between reinforced concrete walls to resist seismic forces if properly designed and detailed.
This document summarizes a study on rehabilitation techniques for existing concrete structures. It discusses various repair methods and materials that can be used, including polymer modified mortar. Non-destructive tests were conducted on a sample structure to evaluate its condition. Based on the results, polymer modified mortar was selected for repairing columns due to its low cost, ease of application, and ability to extend the life of the building for 15-18 years at a lower cost than reconstruction. The study concludes that repairing existing structures using appropriate technologies and materials is more economical than demolition and aims to provide guidance on cost-effective rehabilitation.
Influence of Local Effects on Hold Period Fatigue Assessments for Reel-LayPaul Brett
Local effects at the hang-off clamp (HOC) where a pipeline is held during offshore installation can influence fatigue damage assessments. Finite element analysis found that local frictional slip and insulation compliance reduce the stress concentration factor compared to assuming full fixity. This lower stiffness and added damping were incorporated into dynamic simulations, finding lower predicted fatigue damage than with full fixity. Accounting for local HOC effects more accurately represents pipeline behavior and could allow longer hold periods.
This document proposes an alternative design for constructing the foundations of a new pedestrian bridge across a harbour. It suggests using a temporary sheet pile wall cofferdam that would allow workers to build the pile group and pile cap at the riverbed level, avoiding the need for divers. The cofferdam design is sized at 10x10m and embedded 10m deep. Calculations are presented to check for piping, heaving, and structural failure. A finite element model is also used. It is determined that drains will be needed to reduce water pressures and piping risks. The design of the internal bracing structure and construction sequence are also considered. The cofferdam is concluded to be a feasible alternative construction method for the bridge
This document provides an overview of a book containing 200 questions and answers on practical civil engineering works. The book is intended to arouse interest in graduate engineers, assistant engineers, and engineers regarding technical aspects of civil engineering projects. It covers topics like bridge works, concrete structures, drainage works, earthworks, piers/marine structures, roadworks, pumping stations, reclamation works, water retaining structures, pipe jacking/microtunneling, piles/foundations, and general civil engineering questions. The author's goal is to explain the reasoning behind common engineering practices to help readers better understand the underlying principles.
200 Questions and Answers on Practical Civil Engineering Works [2]_2008.pdfMasi Uddin
This document contains a preface and 12 chapters related to practical questions and answers on various aspects of civil engineering works. The preface states that the book aims to provide graduate engineers and practicing engineers with technical knowledge on current civil engineering practices. It contains over 200 questions and answers selected from the author's monthly journal column on civil engineering topics. The chapters cover various topics related to bridge works, concrete structures, drainage works, earthworks, marine structures, roadworks, pumping stations, reclamation works, water retaining structures, pile foundations, and general civil engineering questions.
Construction of modern buildings requires many pipes and ducts in order to accommodate essential services such as air conditioning, electricity, telephone, and computer network. Web openings in concrete beams enable the installation of these services. A number of studies have been conducted with regards to reinforced concrete beams which contain web openings. The present paper aims to compile this state of the art work on the type of Reinforced Concrete (RC) beams with transverse web openings. Various design approaches and strengthening techniques are also presented.
IRJET- Study on Causes of Cracks and its Remedial Measures in Reinforced Conc...IRJET Journal
The document discusses cracks in reinforced concrete bridge piers and abutments. It first provides background on the causes of cracking, including applied loads, restraint from volume changes, and drying shrinkage. It then presents a case study of a bridge exhibiting cracks in the abutments and approaches. The cracks are thought to be caused by movement of the abutments due to issues with surrounding soils. The document outlines various remedial measures that could address abutment movement and cracking, such as soil grouting, concrete jacketing, and epoxy injection. It concludes that abutment movement must be addressed to prevent further deterioration of the bridge structure.
Flexible thermoplastic culverts like Enviro-Span can withstand much deeper fill depths than rigid materials like steel or concrete due to soil arching effects. Finite element analysis shows Enviro-Span can safely withstand at least 115 feet of fill, which is orders of magnitude more than comparable steel arches. Research also indicates standards like AASHTO are overly conservative, and a 5-foot HDPE pipe can safely withstand over 80 feet of fill. As a thermoplastic, Enviro-Span interacts with soil to form a composite structure that distributes loads more efficiently than rigid materials, allowing it to withstand extremely deep fill depths.
The document discusses stresses around underground openings such as tunnels. It describes how underground openings alter the initial stress state of rocks and how determining stresses is important for design. Different types of tunnels and excavation methods are also outlined. The document then focuses on analyzing stresses around circular underground openings using transformations between rectangular and polar coordinate systems. It presents solutions for circular openings under hydrostatic stress fields and discusses elastic-plastic behavior, including Bray's model for analyzing squeezing tunnels.
This document evaluates utilizing commercially available PVC tubes as compression members filled with concrete. An experimental study tested 4 concrete-filled PVC columns and 2 plain concrete columns as references. The concrete-filled PVC columns exhibited higher strength and ductility than the plain concrete columns. Testing showed that the PVC tubes increased the compressive strength of the concrete core by confining it and allowing for larger lateral deformation before failure. The PVC tubes contained the shear failure of the concrete core at an angle of approximately 45 degrees. The study provides a basis for further research on concrete-filled PVC tubes with varying dimensions and concrete properties.
IRJET- Behavior of Compound Concrete Filled Reinforced PVC Tubes Under Compre...IRJET Journal
This document discusses an experimental study on the compressive behavior of compound concrete filled reinforced polyvinyl chloride (PVC) tubes compared to unreinforced PVC tubes. Compound concrete contains a mixture of fresh concrete and demolished concrete lumps. Ten specimens were tested - two unreinforced and eight with internal steel stirrup reinforcement at varying spacings. Results showed that reinforced specimens had higher load capacity and compressive strength than unreinforced specimens. Closer stirrup spacing led to higher strength. Reinforcement improved the compressive performance of the composite tubes.
Ground improvement technic and repair procedures.pdfKumarS250747
Foundation Design requires the knowledge of the behavior of the structure supported by the foundation as well as that of soil or rock that furnishes the ultimate support.
The super structure, foundation and soil or rock must act together and each must posses its unique serviceability and safety in the interactive system
The soil or rock may provide adequate safety of the foundation against failure, detrimental settlement may occur prior to any collapse. Which may be analogous to beam or truss in super structure but does not meet the serviceability(Deflection) criteria
The super structure designs are controlled by the strength of material such as shear strength ,compressive strength and tensile strength but deformations governs the design of foundation.
This document summarizes chapter 4 of the book "Structural Concrete Design" which covers various topics related to designing structural concrete including:
- Properties of concrete and reinforcing steel such as compressive strength, modulus of elasticity, creep, and tensile strength.
- Proportioning and mixing concrete, including using admixtures.
- Flexural and strength design of beams, slabs, columns, shear/torsion, development of reinforcement, two-way systems, frames, brackets/corbels, and footings.
- Additional concrete types such as lightweight and high-strength concrete.
This document provides an overview of subsea pipeline systems. It discusses the key components including wellhead platforms, risers, pipelines, manifolds, and flowlines. It then describes various types of subsea pipelines and their purposes for transporting hydrocarbons from offshore production units to shore. The rest of the document outlines the major design considerations and analyses performed for subsea pipelines, such as sizing, material selection, mechanical design, stability, crossings, and cathodic protection. Standards and codes used for subsea pipeline design are also listed.
Effect Of Water On Slope Stability And Investigation Of ΝΝw Drainage Techniqu...IJMER
This document summarizes a study on using drainage gravel piles to stabilize landslides along sections of the Egnatia Odos highway in Greece. Drainage gravel piles are vertical wells filled with permeable gravel that act as drains to lower the water table and pore water pressure within landslide-prone areas. The study investigates applying this technique to a landslide zone along the highway underlain by a buried river terrace with high permeability. It describes the geology and groundwater conditions contributing to landslides. Calculations are presented on the expected drawdown cone and impact radius of drainage gravel piles based on pumping test principles. The construction method is outlined. The study concludes drainage gravel piles can effectively drain landslide materials by channeling
1. The document discusses parameters that affect the strength of concrete in externally prestressed bridges. It examines factors like tendon layout, prestressing method, effective depth and eccentricity of external tendons, and materials used for tendons.
2. Studies have found that draped tendon profiles provide higher strength than straight profiles. External prestressing requires more prestressing force than internal prestressing, except for very deep girders. Increased effective depth and eccentricity of external tendons enhances strength.
3. Carbon fiber reinforced polymer tendons are an alternative to steel but have issues with brittleness and cost. Overall, optimizing tendon layout and placement can improve the strength of externally prestressed concrete bridges
Comparative Study on the Design of Square,Rectangular and Circular Concrete W...IJERA Editor
Reinforced concrete overhead water tanks are used to store and supply safe drinking water. Design and cost estimation of overhead water tanks is a time consuming task, which requires a great deal of expertise. This study therefore examines the efficiency of Rectangular and Circular tanks. Tanks of 30m3, 90m3, 140m3 and 170m3 capacities were used in order to draw reasonable inferences on tank‟s shape design effectiveness, relative cost implications of tank types and structural capacities. Limit state design criteria were used for basic tank‟s construction materials- steel reinforcement, concrete and formwork were taken-off from the prepared structural drawings. Results of the material take-offs showed that, for each of the shapes, the amount of each structural materials increase as the tank capacity increases. Also Circular-shaped tank consumed lesser individual material as compared to Rectangular ones. Hence, this will give Circular-shaped tanks a more favoured selection over the rectangular shaped tanks.
Prestressed concrete uses tensioned steel to put concrete in compression and improve its performance. Circular structures like pipes, tanks and poles are well-suited for circular prestressing using hoop tension to counteract internal fluid pressure. Pipes can be made through monolithic, two-stage or precast construction. Design considerations include stresses from handling, support conditions, working pressure and cracking. Tanks come in different shapes and are analyzed as shells. Poles are designed for various loads as vertical cantilevers with tapering cross-sections.
This document discusses the various loads that act on concrete dams, including primary, secondary, and exceptional loads. It provides details on the following primary loads: water load, self-weight load, and seepage loads (internal and external uplift). Secondary loads discussed include sediment load, wave load, wind load, and ice load. Exceptional loads mentioned include seismic and tectonic effects. The document also contains schematic diagrams that illustrate how these loads are distributed on gravity dams and their points of application. Equations are provided for calculating the magnitudes of several load types.
Seismic response of steel beams coupling concrete wallsYahya Ali
The document summarizes an experimental study on the seismic response of steel link beams coupling reinforced concrete walls. Two specimen walls were tested with short span steel beams connecting the walls. The steel beams were designed according to seismic standards to yield in shear and dissipate energy through hysteretic damping. Both specimen walls exhibited excellent ductility and energy absorption. The steel beams remained elastic with minor local buckling. The study demonstrated that steel link beams can provide ductile connections between reinforced concrete walls to resist seismic forces if properly designed and detailed.
Literature Review Basics and Understanding Reference Management.pptxDr Ramhari Poudyal
Three-day training on academic research focuses on analytical tools at United Technical College, supported by the University Grant Commission, Nepal. 24-26 May 2024
ACEP Magazine edition 4th launched on 05.06.2024Rahul
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1. Thin-Walled Structures 39 (2001) 153–165
www.elsevier.com/locate/tws
Stress modeling of pipelines strengthened with
advanced composites materials
Houssam Toutanji *
, Sean Dempsey
Department of Civil and Environmental Engineering, University of Alabama in Huntsville, Huntsville,
AL 35899, USA
Received 13 June 2000; received in revised form 26 October 2000; accepted 26 October 2000
Abstract
Fiber reinforced polymer composites (FRPC) have established a strong position as an effec-
tive mean for the repair and rehabilitation of infrastructure. However, the use of FRP in the
repair and rehabilitation of pipelines is a new concept that has the potential to improve the
way we repair pipelines. The purpose of this paper is to discuss the benefits of using FRPC
and to provide stress expressions on the interaction between the different stresses exerted on
pipe walls and the effects of FRPC sheets on the circumferential stresses of damaged pipe
walls. The effects of three different FRPC sheets: Glass FRP (GFRP), Aramid FRP (AFRP),
and Carbon FRP (CFRP) on the performance of pipe walls will be compared analytically.
Results show that carbon fiber composites perform better than glass or aramid in improving the
ultimate internal pressure capacity of pipes, and therefore, significantly enhance the strength,
durability, and corrosive properties. 2001 Elsevier Science Ltd. All rights reserved.
Keywords: Advanced composites; Corrosion; Durability; Fiber reinforced polymer composites
1. Introduction and background
Engineers are faced with the ongoing task of rehabilitating pipelines due to damage
caused by many environmental and load factors that occur. Not only defects in the
original material or in the manufacturing and installation process such as cracks
during loading, shipping, unloading, or storage cause damage to pipes but also, site
conditions that accelerate corrosion such as fluctuating ground water, low soil resis-
* Corresponding author. Tel.: +1-256-824-6370; fax: +1-256-824-6724.
E-mail address: toutanji@cee.uah.edu (H. Toutanji).
0263-8231/01/$ - see front matter 2001 Elsevier Science Ltd. All rights reserved.
PII: S0263-8231(00)00049-5
2. 154 H. Toutanji, S. Dempsey / Thin-Walled Structures 39 (2001) 153–165
Nomenclature
sf hoop stress due to internal fluid pressure
p internal fluid pressure
r radius of pipe
t thickness of pipe wall
ss bending stress due to soil load
Cd calculation coefficient for earth load
g unit weight of soil backfill (N/mm3
)
Bd width of ditch at the level of top of pipe
E modulus of elasticity of pipe
km bending moment coefficient dependent on the distribution of vertical
load and reaction
kd a deflection coefficient dependent on the distribution of vertical load
and reaction
st bending stress due to traffic load
Ic impact factor
Ct surface impact load coefficient
F wheel load on surface
A effective length of pipe on which load is computed
sm the maximum circumferential tensile stress at the critical sections
d maximum defect depth
k a multiplying constant
T time at exposures
n an exponential constant
tt thickness of pipe wall and FRP sheets
tivity, and high soil alkalinity. By utilizing conventional rehabilitation methods such
as shortcrete, polymer concrete composites, and the trenchless method, concrete pipe-
lines and manhole rehabilitation in the US is estimated between $1 and 1.5 billion,
and natural gas pipeline rehabilitation is estimated at $530 million. With the ever
increasing uncertainty in the reliability of these existing repair methods, there is a
need for the development of a rapid and cost effective method of repairing pipelines
without excavation of overlaying soil and/or replacement of pipe sections. This need
has led to the potential use of advanced composite materials.
Advanced composites are lightweight, they have a high specific strength, they
provide a long corrosive resistance, and have a high level of durability. With an
increased tailorability and rapid installation, advanced composites do not require soil
excavation, removal of existing pipe, and are easy to carry into and applied onto
existing pipe surfaces. Pipe diameter is not excessively decreased and flow capacity
has been known to increase in some cases due to the smooth final coating that causes
less friction than some pipe material such as concrete [1].
3. 155
H. Toutanji, S. Dempsey / Thin-Walled Structures 39 (2001) 153–165
1.1. Composite application schemes
Currently two methods of applying FRP to damaged pipes exist. First, adhesion
of pultruded sections, which is most appropriate for simple shapes and has relatively
even substrate, consists of a prefabricated composite section adhesively bonded to
the pipe surface. Second, wet lay-up, which is most appropriate for complex shapes
or uneven surfaces, or when very high bond strength is required consists of the
addition of composites to existing pipe using in situ processing techniques. Both
methods require a clean dry pipe surface with an average ambient temperature of
65°F (18°C) to apply adhesives to the pipe [1].
Winding machines to wrap hollow bodies with thermoplastic composite tapes have
been on the market for many years, and are used in the production of ultralight
military tanks and in the aerospace industry. The operation is carried out in a work-
shop, by placing the tape on a thin-walled cylinder that rotates around its axis. The
winding is consolidated by heating the tape above the melting temperature of the
matrix resin, usually by flame or laser beam, just before setting it in place. Such a
technique, however, cannot be used to repair gas pipelines for several reasons. The
most obvious reasons are that the hollow body cannot be rotated, the use of free
flames and high-pressure oxygen–hydrogen bottles close to a damaged pipeline are
not allowed for safety reasons, the use of a laser beam would require equipment that
cannot be operated in the field, and the adaptation of the existing hooping machines
would be too complex. To overcome these difficulties, a relatively simple orbiting
winding machine that requires the pipe to be excavated and its operation carried out
in a workshop, was developed. This winding machine can be transported and
mounted on the pipe to be repaired in situ. These machines wind the composite
tape with pretensions of up to 1500 N and delivery speeds of up to 60 m/min. The
circumferential pretensions applied during the winding converts into radial stress.
This in turn counterbalances the internal pressure (Fig. 1) [2].
Fig. 1. Schematic of the repairing (a) and section of the wound pipe (b).
4. 156 H. Toutanji, S. Dempsey / Thin-Walled Structures 39 (2001) 153–165
2. Theoretical model and analysis
2.1. Theoretical model
Pressurized underground pipelines must resist both internal and external pressures.
To determine the effect of FRP repairs on a pipe wall, stress expressions will have
to be developed and applied to undamaged pipe, damaged pipe, and FRP reinforced
damaged pipes. This will in turn produce an overall expression for the maximum
circumferential tensile stress at a critical section that contains different loading such
as soil, traffic, and internal pressure. Pipelines that withstand loads such as traffic
loads, are subjected to externally applied stresses that are not uniform on any specific
cross section nor are they uniform along the length of the pipe. In this theoretical
model, the support and loading variations along a run of pipe will be assumed to
be indistinguishable at a specific cross section where the longitudinal load variation
will be ignored. It will also be assumed that the pipeline will remain at a constant and
uniform temperature with its cross section in a state of plain strain (i.e. longitudinal
movements or deformations being ignored) [3].
Pipelines are not only faced with internal and external pressures, but are also
subjected to internal and external corrosion. With either a uniform or localized nat-
ure, corrosion affects the pipe wall thickness. Literature review shows that one diffi-
cult aspect of repair of pipe walls is the problem of uncertainty in predicting the
location rate of corrosion [3]. This problem should be of consideration for both
proper design practices and for making decisions about pipeline maintenance and
repair strategies.
2.2. Wall stresses in underground pressurized undamaged pipes
The effects of stresses exerted by external soil pressure and by internal fluid press-
ure on underground-pressurized pipelines should be considered. Internal pressure
produces uniform circumferential tension across the wall if the wall thickness is
comparatively small and the density of the fluid carried in the pipeline is small
relative to the fluid pressure. Bending stresses both in the longitudinal and circumfer-
ential directions are produced by external loads. This circumferential stress is the
main focus since the pipe is assumed uniformly loaded and supported along its
length. Circumferential bending stresses are usually less critical on the sides of a
pipe where they are of higher importance on the top and bottom of the pipe [4]. If
the pipe wall stresses remain within the elastic range of the material, the circumfer-
ential bending stresses in the pipe wall due to the external loads are assumed to be
algebraically additive to the tensile circumferential (i.e. hoop) stress produced by the
internal pressure.
The circumferential stress due to internal pressure can be estimated using the
following expression
sf⫽
pr
t
(1)
5. 157
H. Toutanji, S. Dempsey / Thin-Walled Structures 39 (2001) 153–165
where it is assumed that t¿r and where sf=hoop stress due to internal fluid pressure;
p=internal fluid pressure; r=radius of pipe; and t=thickness of pipe wall.
The bending stress in the circumferential direction produced in the pipe wall by
the external soil loading can be estimated using Eq. (2) [5]
ss⫽
6kmCdgB2
dEtr
Et3
+24kdpr3 (2)
where ss=bending stress due to soil load (MPa); Cd=calculation coefficient for earth
load; g=unit weight of soil backfill (N/mm3
); Bd=width of ditch at the level of top
of pipe (m); E=modulus of elasticity of pipe (MPa); km=bending moment coefficient
dependent on the distribution of vertical load and reaction (MPa); and kd=a deflection
coefficient dependent on the distribution of vertical load and reaction.
When an external traffic load such as roadway, railway, or airplane traffic exist,
the resulting circumferential bending stresses produced in the pipe wall may be esti-
mate from
st⫽
1
A
6kmIcCtFEtr
(Et3
+24kdPr3
)
(3)
where st=bending stress due to traffic load (MPa); Ic=impact factor; Ct=surface
impact load coefficient; F=wheel load on surface (N); and A=effective length of pipe
on which load is computed (m).
The maximum circumferential tensile stress sm at the critical sections can be
expressed by the following if the pipe wall remains in the elastic range under load
sm⫽sf⫹ss⫹st (4)
sm⫽
pr
t
⫹
6kmCdgB2
dEtr
Et3
+24kdpr3
⫹
6kmIcCtFEtr
A(Et3
+24kdPr3
)
(5)
2.3. Wall stresses in underground pressurized damaged pipes
Internal corrosion is dependent on the pipes internal fluid properties and their
interaction with the pipes own material. This interaction between the fluid properties
and pipe material may cause potential and/or chemical changes as the fluid flows
through the pipeline. Evidence shows that internally uniform corrosion is less likely
to occur, where localized corrosion on the surrounding exterior surface is more likely.
External corrosion is dependent on the localized condition, including the soil type,
rate of oxygen depletion and replenishment, soil water or moisture and its movement,
and presence and effectiveness of any corrosion protection measures. The loss of
pipe wall thickness due to corrosion may be relatively uniform in extent or localized,
but does not occur at a constant rate over the design life of the pipe. Protective
properties of the corrosion product improve after the initial corrosive period. This
initial period of wall thickness corrosion is due to the corrosion products that are
6. 158 H. Toutanji, S. Dempsey / Thin-Walled Structures 39 (2001) 153–165
formed on the pipe surface being porous and their protective properties being poor.
The corrosion rates after this initial period gradually decreases and in some cases
stabilizes. Thus, with time the loss of wall thickness increases. Developing
expressions with a function of time in a general corrosive case, whether this means
weight loss, deepest pit or localized depth, or average pit or localized depth, can be
modeled empirically by a power law [6].
d⫽kTn
(6)
This law should be understood as an engineering viewpoint rather than a scientific
viewpoint where d=maximum defect depth; k=a multiplying constant; T=time at
exposures; and n=an exponential constant. For soil conditions, corrosion of steel, k
ranges from 0.1 to 0.5 and n may vary from 0.4 to 1.2 [6].
Applying this power law to the previous circumferential stress Eqs. (1)–(3), can
be estimated using the following expressions. The circumferential stress equation
due to internal pressure then becomes the following expression when applied to a
damaged pipe
sf⫽
pr
t−d
(7)
The bending stress in the circumferential direction produced in the pipe wall by
the external soil loading is then expressed by
ss⫽
6kmCdgB2
dE(t−d)r
E(t−d)3
+24kdpr3
(8)
Therefore, the circumferential bending stress produced in the pipe wall with an
external traffic load is expressed by
st⫽
6kmIcCtFE(t−d)r
A(E(t−d)3
+24kdpr3
)
(9)
sm⫽sf⫹ss⫹st (10)
2.4. Wall stresses in underground pressurized frp reinforced damaged steel pipes
Applying the properties, equations, and theory behind the wall stresses in under-
ground pressurized damaged pipes, expressions are developed to include the addition
of fiber reinforced polymer composites (FRP) for repair and rehabilitation of pipe-
lines. Using FRP to repair and rehabilitate damaged pipe causes t (thickness of pipe)
to change. The following expression takes into consideration FRP addition and is
substituted for t as tt [7].
7. 159
H. Toutanji, S. Dempsey / Thin-Walled Structures 39 (2001) 153–165
Fig. 2. Circumferential stresses due to soil load, traffic load, and internal pressure in pipe without defects.
tt⫽(ts⫺d)冋1⫹
EFRPtFRP
Es(ts−d)册 (11)
Thus, with the consideration of FRP addition to the pipe wall thickness, the follow-
ing expressions are developed for the circumferential stress due to internal pressure
and the bending stress in the circumferential direction produced in the pipe wall by
the external soil loading
sf⫽
pr
(ts−d)冋1+
EFRPtFRP
Es(ts−d)册
(12)
ss⫽
6kmCdgB2
dEsttr
Et3
t +24kdpr3 (13)
8. 160 H. Toutanji, S. Dempsey / Thin-Walled Structures 39 (2001) 153–165
Fig. 3. Circumferential stresses due to soil load, traffic load, and internal pressure in damaged pipes.
The circumferential bending stress produced in the pipe wall with an external traffic
load with the addition to the FRP sheets
st⫽
6kmIcCtFEttr
A(Et3
t +24kdpr3
)
where tt⫽(ts⫺d)⫹ntFRP (14)
sm⫽sf⫹ss⫹st (15)
2.5. Example application and analysis
The purpose of this example application is to illustrate that the basis of this model
is realistic and solid. To generate the circumferential stress analytical curves, it is
necessary to know the internal fluid pressure, the pipe radius, the various constants,
the elastic modulus, and the thickness of fiber sheets. This and other necessary data
to use in conjunction to the developed model are provided in Tables 1 and 2. Table
1 summarizes the constraints and mechanical properties of a given length of pipe to
9. 161
H. Toutanji, S. Dempsey / Thin-Walled Structures 39 (2001) 153–165
Fig. 4. Circumferential stresses due to soil load, traffic load, and internal pressure in CFRP repaired
damaged pipes.
develop plotted curves stresses due to soil, traffic, and internal pressure. Table 2
shows the mechanical properties of FRP sheets.
The analytical results obtained from the model are shown in Figs. 2–5. Fig. 2
shows the comparison of circumferential stresses due to soil load, traffic load, and
internal pressure in an undamaged pipe, Fig. 3 shows the same comparisons but in
a damaged pipe. As expected, a pipe without defects withstand higher stresses due
to soil and traffic loads and lower stresses due to internal pressure than a pipe with
defects. For example, in the pipe without defect, the circumferential stress due to
internal pressure is 182.4 MPa with an internal pressure of 4 MPa, whereas in the
damaged pipe, the stresses are 304 and 4 MPa respectively. The circumferential
stress due to traffic in the pipe without defects at an internal pressure of 4 MPa is
112.6 MPa, whereas in the damaged pipe the stress is 77.7 MPa.
The question is “what benefits do FRP composite sheets provide in a pipe circum-
ferential stresses?” and if they do provide benefit “what type of FRP sheet (CFRP,
GFRP, or AFRP) has a greater ultimate internal pressure?” Fig. 4 shows, as an
example, the circumferential stresses of the CFRP repaired damaged pipe due to the
10. 162 H. Toutanji, S. Dempsey / Thin-Walled Structures 39 (2001) 153–165
Fig. 5. Comparison between circumferential stress and internal pressure in pipe without defect, pipe
with defect, and (GFRP, CFRP, and AFRP) repaired damaged pipe.
soil and traffic loads as well as to internal pressure. The curve shows a significant
increase in the stresses due to soil and traffic loads and a decrease in the stress due
to internal pressure when compared to Fig. 3.
Fig. 5 shows a comparison between the maximum circumferential stress, sm, (
sf+ss+st) and internal pressure in pipe without defect, pipe with defect, and GFRP,
CFRP, and AFRP repaired damaged pipe. The curve shows the benefits that FRP
sheets provide for the pipe strength with CFRP. Fig. 6 compares the undamaged
pipe, damaged pipe, and pipes repaired with the three different FRP sheets, to their
ultimate internal pressure (MPa). Again it is clear that the pipe repaired with carbon
fiber sheets has a higher stress threshold than those repaired with glass or aramid fib-
ers.
11. 163
H. Toutanji, S. Dempsey / Thin-Walled Structures 39 (2001) 153–165
Table 1
Mechanical properties and constraints of a given length of pipe
Symbol Description Value
r Pipe radius, (mm) 228
t Pipe wall thickness, (mm) 5
Km Bending moment coefficient 0.235
Cd Calculation coefficient for earth load 1.32
g Unit Weight of soil, (N/mm2
) 18.85×10−6
Bd Width of ditch at the level of top of pipe, (mm) 762
E Module elasticity of pipe, (N/mm2
) 200,000
kd Deflection coefficient 0.108
Ic Impact factor 1.5
Ct Surface load coefficient 0.12
F Wheel load on surface, (N) 267,000
d Maximum defect depth, (mm) 2
A Effective length of pipe, (mm) 914
Table 2
Mechanical properties of FRP sheets
Specimens Thickness, t (mm) Hoop strength (MPa) Modulus of elasticity
(GPa)
Glass 0.118 1500 74
Aramid 0.193 2100 120
Carbon 0.165 300 400
3. Conclusion
This paper concentrates on establishing fiber reinforced polymer composites as an
effective mean for the repair and rehabilitation of pipelines. This objective was
reached by developing a theoretical model with stress expressions and circumfer-
ential stress curves. The stress expressions were developed to study the interaction
between the different stresses exerted on pipe walls and the effects of FRP sheets
on the circumferential tensile stress of damaged pipe walls. The stress curves dis-
played the maximum circumferential tensile stresses due to soil loads, traffic loads
and the pipes internal pressure. These curves were analyzed and their results showed
that carbon fiber sheet provides a better performance than glass or aramid in improv-
ing the ultimate internal pressure capacity of pipes. This study was focused on the
application of fiber reinforced polymer on steel pipes. Steel may corrode in the pres-
ence of carbon fiber material. However, earlier studies have not shown any visible
degradation when polymeric material contacts steel. Thus, before applying FRP on
damaged steel pipe walls, the walls must be free of corrosion and well coated to
prevent the contact between FRP and the steel.
12. 164 H. Toutanji, S. Dempsey / Thin-Walled Structures 39 (2001) 153–165
Fig. 6. Comparison between pipe status and ultimate internal pressure in pipe without defect, pipe with
defect, and (GFRP, CFRP, and AFRP) repaired damaged pipes.
Acknowledgements
The authors would like to acknowledge the financial support of the National
Science Foundation CAREER Grant No. CMS-9796326.
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