Mechanical Behavior of Steel Pipe Bends: An Overview

Karamanos, Spyros A.

doi:10.1115/1.4031940

Cited by 48 publications

(24 citation statements)

References 47 publications

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“…The value of axial force F is normalized by the nominal yield force of the pipe cross-section F P ¼ r Y pDt ð Þ , whereas the corresponding axial displacement u is normalized by the pipe diameter. The results indicate an increase of bend flexibility as the bend angle a increases, which is in accordance with similar observations from ''on-air'' (not embedded) elbow tests and numerical results (Karamanos 2016). In the same figure, the results for the three elbows are compared with the corresponding results from a straight pipe (bend angle equal to zero).…”

Section: Elbow Performance In Terms Of Limit Statessupporting

confidence: 78%

“…The tests in Varelis et al (2013) and Varelis and Karamanos (2015) were also supported by extensive numerical simulations that employed advanced cyclic plasticity models, also reported in Varelis et al (2013) and Varelis and Karamanos (2015), and simplified analytical methodologies for the low-cycle fatigue design of the elbows. For an overview on the mechanical behavior of steel pipe bends, the reader is referred to the recent paper by Karamanos (2016).…”

Section: Introductionmentioning

confidence: 99%

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Structural behavior of buried pipe bends and their effect on pipeline response in fault crossing areas

Vazouras

Karamanos

2017

Bull Earthquake Eng

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Pipe bends, often referred to as ''elbows'', are special pipeline components, widely used in onshore buried steel pipelines. They are sensitive to imposed deformations and their structural behavior is quite flexible and associated with the development of significant stress and strain, which may lead to failure. In the present paper, the mechanical performance of buried steel pipeline bends is investigated first, using rigorous finite element models that account for the pipe-soil interface. Three 36-inch-diameter pipe elbows are considered, subjected to pull-out force and embedded in cohesive soils. The elbows have bend angles equal to 90°, 60°and 30°, and bend radius-over-diameter ratio (R/D) equal to 5. The results show the increased flexibility of the pipeline bend with respect to the straight pipe, and are reported in the form of force-displacement diagrams. Furthermore the deformation limits of each elbow are identified in terms of appropriate performance criteria. The second part of the paper investigates the effect of pipe bends on the response of pipelines crossing active faults using a three-dimensional rigorous finite element model. The numerical results refer to a 36-inch-diameter pipeline crossing a strike-slip fault, and show that the unique mechanical response of pipe bends, in terms of their flexibility, may offer an efficient tool for reducing ground-induced deformations. The three-dimensional model employs the load-displacement curves of the first part of the paper as end conditions through nonlinear springs. Furthermore, the results show that there exist an optimum distance of the elbow from the fault plane, which corresponds to the maximum allowable ground displacement. Therefore, pipeline elbows, if appropriately placed, can be employed as ''mitigating devices'', reducing ground-induced action on the pipeline at fault crossings.

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Section: Elbow Performance In Terms Of Limit Statessupporting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Structural behavior of buried pipe bends and their effect on pipeline response in fault crossing areas

Vazouras

Karamanos

2017

Bull Earthquake Eng

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“…Lr=θ θ,max/0 (7) with  0 = y + ul /2 (8)  y is the yield stress, ult the ultimate stress. In FAD, failure is given by the following condition; if the assessment point of coordinate * * [ , ] r r L k is under the failure curve given by the following equation , = , ) where the subscript c indicates critical condition , the structure is safe.…”

Section: =75° =90°imentioning

confidence: 99%

“…Indeed, the piping systems including the elbows are subjected to severe factors which may menace the integrity and safety of the pipe [4][5]. Due to the importance of elbows in the petroleum industries including their geometry and location, they are considered to be as critical parts in piping systems [6][7]. Due to their geometry, stress amplification occurs which promote failure and leak.…”

Section: Introductionmentioning

confidence: 99%

Numerical study of semi-elliptical cracks in the critical position of pipe elbow

Muthanna

Bouledroua

Meriem-Benziane

et al. 2019

Frattura Ed Integrità Strutturale

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Pipelines are considered as a major tool to transport hydrocarbons due to its important role in transporting fluids taking into account the operating conditions. Despite the importance of the elbow which considered as a critical part in the pipelines, the repeated failures and defects became a dangerous and enormously costly issue. In this numerical study, the Fluid-Structure Interaction (FSI) analysis was carried out using Ansys software. This work is divided into four main parts: the first part focused on studying and comparing the effect of bending radius of pipe elbow on the maximum of Von-Mises stress values for each radius with the yield stress of the steel of the pipe. The second part focused on the creation of a semielliptical crack for different locations along the elbow angles to show the critical position compared to the stress intensity factors. In the third part, the Citation: Muthanna, B. G. N., Bouledroua, O., Meriem-Benziane, M., Hadj Meliani, M.,

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“…More recently, the low-cycle fatigue of pipe elbows, subjected to severe cyclic loading, has been investigated experimentally and numerically by Varelis et al [11], [12]. The recent paper by Karamanos [13] offers an overview of pipe elbow mechanical behavior under severe loading conditions.…”

Section: Introductionmentioning

confidence: 99%

CFRP Reinforcement and Repair of Steel Pipe Elbows Subjected to Severe Cyclic Loading

Skarakis

Chatzopoulou

Karamanos

et al. 2017

Journal of Pressure Vessel Technology

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In order to ensure safe operation and structural integrity of pipelines and piping systems subjected to extreme loading conditions, it is often necessary to strengthen critical pipe components. One method to strengthen pipe components is the use of composite materials. The present study is aimed at investigating the mechanical response of pipe elbows, wrapped with carbon fiber-reinforced plastic (CFRP) material, and subjected to severe cyclic loading that leads to low-cycle fatigue (LCF). In the first part of the paper, a set of LCF experiments on reinforced and nonreinforced pipe bend specimens are described focusing on the effects of CFRP reinforcement on the number of cycles to failure. The experimental work is supported by finite element analysis presented in the second part of the paper, in an attempt to elucidate the failure mechanism. For describing the material nonlinearities of the steel pipe, an efficient cyclic-plasticity material model is employed, capable of describing both the initial yield plateau of the stress–strain curve and the Bauschinger effect characterizing reverse plastic loading conditions. The results from the numerical models are compared with the experimental data, showing an overall good comparison. Furthermore, a parametric numerical analysis is conducted to examine the effect of internal pressure on the structural behavior of nonreinforced and reinforced elbows, subjected to severe cyclic loading.

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Mechanical Behavior of Steel Pipe Bends: An Overview

Cited by 48 publications

References 47 publications

Structural behavior of buried pipe bends and their effect on pipeline response in fault crossing areas

Structural behavior of buried pipe bends and their effect on pipeline response in fault crossing areas

Numerical study of semi-elliptical cracks in the critical position of pipe elbow

CFRP Reinforcement and Repair of Steel Pipe Elbows Subjected to Severe Cyclic Loading

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