Seismic fragility analysis of seismically isolated nuclear power plants piping system

Firoozabad, Ehsan Salimi; Jeon, Bub-Gyu; Choi, Hyoung-Suk; Kim, Nam-Sik

doi:10.1016/j.nucengdes.2014.12.012

Cited by 32 publications

(6 citation statements)

References 20 publications

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“…Lack of code provisions or due to the complexity of modelling causes engineers to overlook important design aspects ensuing over or underestimate the seismic risk. Regarding the development of decoupled fragility curves, simplified analysis can be carried out without considering the dynamic interaction, as done by Firoozabad et al (2015) for piping systems of nuclear power plants (NPP) and by Park and Lee (2015) for boil-off gas compressors at LNG terminals. An elbow and an anchor point (in former case) were identified as the critical section of the system.…”

Section: Figure 1 Overview Of Refrigerated Liquefied Gas (Rlg) Plantmentioning

confidence: 99%

Seismic fragility analysis of LNG sub-plant accounting for component dynamic interaction

Farhan

Bousias

2020

Bull Earthquake Eng

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Earthquakes can cause significant damage to Liquefied Gas terminals, a critical part of lifeline facilities of energy supply networks, failure of which may lead to loss of hazardous material, explosion, environmental contamination, loss of functionality and disruption of business. To date, seismic risk analysis of such facilities mainly focuses at component level, with the inherent dynamic interaction between the supporting structure and non-structural components not receiving the merited attention.In the present study, the seismic performance of an actual facility comprising of a piping system and a supporting structure is analyzed through a detailed 3D finite element model in the nonlinear regime, both as coupled and decoupled cases. Plastic strains are used as Engineering Demand Parameters (EDP) to define leakage limit state for pipes. Since the reinforced concrete (RC) pipe rack supporting structure is designed for low seismic loads, shear is recognized as the predominant failure mode. The same components are then analyzed in unison, considering coupling due to dynamic interaction. Fragility functions are evaluated for both cases using Multiple Stripe Analysis. A set of 250 strong ground motions artificially generated using the Specific Barrier Model, are employed for developing fragility curves. They are expressed with peak ground acceleration (PGA) as an intensity measure. Statistical estimation of the parameters of fragility functions are based on maximum likelihood method. It is inferred that in the decoupled case, pipelines show higher vulnerability at lower PGA, at higher PGA pipe rack can fail abruptly resulting in total failure of the system. Moreover, in coupled case the fragility of the pipes and RC rack changes substantially because of the piping system boundary conditions. Thus, concluding that the risk estimation could be erroneous if dynamic interaction is neglected.

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Section: Figure 1 Overview Of Refrigerated Liquefied Gas (Rlg) Plantmentioning

confidence: 99%

Seismic fragility analysis of LNG sub-plant accounting for component dynamic interaction

Farhan

Bousias

2020

Bull Earthquake Eng

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“…To-date, it still remains to be examined the dynamic interaction between a supporting structure and a piping system towards highlighting the most critical design challenges and preventing accidents in the future that put human lives and environment at risk. To the best of our knowledge, the research is rather limited on this topic; the majority of research has focused on the analysis of piping system or critical components individually ( [5] & [16] among others), whereas the analysis of the combined models (supporting structure and piping) is rather obscure. An interesting research upon the effects of dynamic interaction on pipe-way and piping system response by considering different weight ratio, diameters and end-condition of pipes as well as thickness of U-ring elements (they are used to capture the pipes along the perimeter restraining only the movement in vertical and transverse direction) was conducted in [17].…”

Section: Previous Studiesmentioning

confidence: 99%

“…To-date, the seismic research has focused on the decoupled case by investigating the seismic response of critical components such as elbows, t-joints or bolted flange joints without analyzing the rack and piping system in unison (coupled case) ( [5], [6]). This engineering practice of decoupling the response of structural and nonstructural components has been adopted not only for research purposes but also in industrial sector in virtue of simplifying the design process due to the lack of code provisions or due to possible limitation of structural analysis software in the market that causes engineers to overlook important design aspects and overestimate or underestimate the seismic response.…”

Section: Introductionmentioning

confidence: 99%

Seismic Fragility Assessment of LNG Pipe Rack Accounting for Soil-Structure-Interaction

Sarno¹,

Karagiannakis²

2019

Proceedings of the 7th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COM

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The increasing momentum for Natural Gas exploitation in Europe and worldwide constitutes Liquified Gas terminals indispensable links of energy supply network. Infrastructures of this kind should be resilient against the earthquake hazard and thus designed accounting for as much as possible sources of uncertainty such as modelling issues, analysis methods, seismic input selection, soil effects and others. To date, research efforts have not assessed the response of pipe racks sufficiently, let alone the interaction between the rack and piping system and analysis methods of the past have proved to be neither adequate nor efficient towards evaluating the earthquake hazard potentiality. Further, soil-structure-interaction has not been incorporated into a fragility analysis framework; albeit it is considered as a critical parameter since midstream and downstream facilities are usually rested on alluvial deposits. In the present work, a supporting RC rack is analysed through a 3D finite element model in the nonlinear regime both as coupled and decoupled vis-à-vis a piping system. The fragility functions are evaluated for structural components and limit states in the global and meso-scale, through the Incremental Dynamic Analysis (IDA) considering far-field conditions. In the end, the SSI is encountered accounting for linear and nonlinear soil, and soil effects are demonstrated by the fragility curves. It is inferred that the fragility of the rack soars considerably by the piping system boundary conditions in the coupled case and the SSI has detrimental impact, and thus should be accounted, particularly, for industrial structures that are located at coastal sites.

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“…6 shows the times-elastic-slope method indicated in ASME BPVC 2010. There are many examples in the literature of using the TES method to restrict the maximum allowable load of elbows (Firoozabad et al, 2015).…”

Section: Limit Loadmentioning

confidence: 99%

“…A comparison of existing plastic collapse load solutions with experimental data for 90° elbows (Han et al, 2012) was performed to compare with existing methods of deriving collapse loads for 90° elbows. The limit load value was also determined for a seismic fragility analysis of a seismically isolated nuclear power plant's piping system (Firoozabad et al, 2015) using the TES method to identify the critical points in the system. The simulation results were validated with a monotonic and cyclic test of the critical points, and the conditional mean spectrum method was used to scale the selected records.…”

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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Seismic fragility analysis of seismically isolated nuclear power plants piping system

Cited by 32 publications

References 20 publications

Seismic fragility analysis of LNG sub-plant accounting for component dynamic interaction

Seismic fragility analysis of LNG sub-plant accounting for component dynamic interaction

Seismic Fragility Assessment of LNG Pipe Rack Accounting for Soil-Structure-Interaction

Condition assessment of damaged elbow in subsea pipelines

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