Shakedown limit loads for elbows under internal pressure and cyclic in-plane bending

Oh, Chang Sik; Kim, Yun Jae; Park, Chi Yong

doi:10.1016/j.ijpvp.2007.11.009

Cited by 25 publications

(7 citation statements)

References 26 publications

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“…Further calculations are carried out by C.S Oh et al [14] for the shakedown of bends covering a large range of h for internal pressure and in-plane closing and opening bending (reversed bending and thermal loading is not considered). In [14], the same lower bound numerical technique is used as in [13], which is thought by the authors of this work to give solutions which are too conservative when compared to the exact shakedown limit solution.…”

Section: Shakedown Analysismentioning

confidence: 99%

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Shakedown and limit analysis of 90° pipe bends under internal pressure, cyclic in-plane bending and cyclic thermal loading

Chen

Ure

et al. 2011

International Journal of Pressure Vessels and Piping

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The Linear Matching Method is used to create the shakedown limit and limit load interaction curves of 90 degree pipe bends for a range of bend factors. Two load cases are considered i) internal pressure and in-plane bending (which includes opening, closing and reversed bending) and ii) internal pressure and a cyclic through wall temperature difference giving rise to thermal stresses.The effects of the ratios of bend radius to pipe mean radius (R/r) and mean radius to wall thickness (r/t) on the limit load and shakedown behaviour are presented.

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Section: Shakedown Analysismentioning

confidence: 99%

“…In [14], the same lower bound numerical technique is used as in [13], which is thought by the authors of this work to give solutions which are too conservative when compared to the exact shakedown limit solution.…”

Section: Shakedown Analysismentioning

confidence: 99%

Shakedown and limit analysis of 90° pipe bends under internal pressure, cyclic in-plane bending and cyclic thermal loading

Chen

Ure

et al. 2011

International Journal of Pressure Vessels and Piping

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“…Extensive research works have been reported in the literature and experiments on shakedown limit and limit load of a single pipe elbow under the combined cyclic and steady loading [10,11]. Recently, a couple of works have been published for more complex piping geometries such as ninety degree back-to-back pipe bends [12,13].…”

Section: Introductionmentioning

confidence: 99%

Cyclic Plasticity Behavior of 90° Back-to-Back Pipe Bends Under Cyclic Bending and Steady Pressure

Cho

Chen

2018

Volume 9: Student Paper Competition

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Back-to-back pipe bends are widely adopted applications in many industries including nuclear sectors. Evaluation of their load bearing capability under complex cyclic loading is very important. Recently, a couple of research reported shakedown boundary of a 90° back-to-back pipe bends by adopting a conservative approach but no comprehensive post yield structural behaviors have been dealt with. In this research the concerning pipe bends subjected to cyclic opening in-plane (IP)/out-of-plane (OP) bending and steady internal pressures are analyzed to construct shakedown and ratchet limit boundary by means of the Linear Matching Method. Analyzed results present that the concerning pipe bends under out-of-plane bending has higher resistance to cyclic bending than under in-plane bending. In additions, the out-of-plane bending causes very small alternating plasticity areas, unlike the in-plane bending. Full cyclic incremental analyses known as step-by-step analysis are performed to verify the structural responses either side of each boundary and confirm correct responses. Parametric studies are carried out with respect to changes in geometry of the concerning pipe bends subjected to the same loading, and semi-empirical equations are derived from relationships of the reverse plasticity limit and the limit pressure with the bend characteristic. This paper offers broad understandings of structural responses of the 90° back-to-back pipe bends under the complex cyclic loading as well as providing key points to be considered for the life assessment of the piping system.

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“…The fragility curves of the NPP piping system were estimated and the computation of the fragility parameters was addressed. Elastic, shakedown and plastic limit loads for 90° elbows under constant internal pressure and cyclic in-plane bending were presented via FEA (Oh et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Condition assessment of damaged elbow in subsea pipelines

Lee

Seo

Paik

2016

Ships and Offshore Structures

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The evaluation of the performance of aged structures is essential in the oil and gas industry, where inaccurate predictions of structural performance may lead to significant hazardous consequences. Elbows are critical structures subject to continuous corrosion that can lead to a burst or collapse. It is important to be able to predict both burst strength in continually corroding structures and the behaviour of the structures after critical corrosion takes place. Structural failures due to a significant reduction in wall thickness make it very complicated for pipeline operators to maintain pipeline serviceability. This paper discusses the plastic limit pressure of elbows without defects and with several local thinned areas. Finite element analysis (FEA) and the Goodall formula were used to evaluate the new formula. The results of the FEA show that the limit load of elbows under internal pressure differs with position and depth of damage. An empirical formula for the limit load of elbows with local thinned areas is proposed. Eight sizes of elbow were considered in this study, with Rm/t of 5, 6, 7.5, 9, 12, 15, 20 and 25. This range covers most of the piping used in high-pressure environments, such as nuclear and subsea situations. The method of numerical analysis was validated by experiment and with FEA results from the literature. The results of the study can be applied to both the operation and assessment of pipelines. A formula to predict the maximum burst strength of damaged elbows is presented, which will enable more accurate estimates of the time until pipelines need to be replaced or repaired .

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Shakedown limit loads for elbows under internal pressure and cyclic in-plane bending

Cited by 25 publications

References 26 publications

Shakedown and limit analysis of 90° pipe bends under internal pressure, cyclic in-plane bending and cyclic thermal loading

Shakedown and limit analysis of 90° pipe bends under internal pressure, cyclic in-plane bending and cyclic thermal loading

Cyclic Plasticity Behavior of 90° Back-to-Back Pipe Bends Under Cyclic Bending and Steady Pressure

Condition assessment of damaged elbow in subsea pipelines

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