Probabilistic Fatigue Reliability of Large Diameter Steel Catenary Risers (SCR) for Ultra-Deepwater Operations

2007 ◽  
Author(s):  
U. O. Akpan ◽  
T. S. Koko ◽  
P. A. Rushton ◽  
A. Tavassoli ◽  
M. Else
Keyword(s):  
Fatigue Strength ◽  
Case Studies ◽  
Material Properties ◽  
Large Diameter ◽  
Random Variables ◽  
Fatigue Reliability ◽  
Strength Parameters ◽  
Stress Levels ◽  
Steel Catenary Risers

For deepwater development in the Gulf of Mexico, steel catenary risers (SCRs) supported from both SPAR and semi-submersible platforms have proven to be successful solutions for in-field flowlines, tie-backs, and export systems. It is envisaged that this will continue to be a promising solution in ultra deep-water applications, up to and beyond 10,000 ft. The study, commissioned by the Mineral Management Service (MMS), investigated the reliability of large-diameter SCRs in ultra-deepwater operations. The primary damage mode considered is fatigue failure. A probabilistic methodology for fatigue reliability is developed, which utilizes deterministic cumulative fatigue damage indicators, namely the stress levels and cycles associated with the various sea states and the fatigue strength of the members. Uncertainties in structural load and material properties are accounted for by assigning probability distributions and standard deviations to the deterministic stress levels. Furthermore, fatigue strength parameters, Miner’s indices, and capacities are modeled as random variables. First order reliability method (FORM) is employed for estimating fatigue reliability. The methodology is applied to three deterministic case studies presented by Intec Engineering (2006a, 2006b). The case studies involved either a SPAR or a semi-submersible platform. For the sake of brevity, a case study involving only a SPAR platform is presented in this paper. The effect of uncertainties in parameters on fatigue reliabilities is investigated. It is observed that the fatigue reliability estimates followed similar trends as the deterministic cumulative damage results, and hence can be used to complement deterministic estimates. Additional benefit and insight gained from the probabilistic study, which can be used for design decisions, include information regarding probabilistic importance and probabilistic sensitivity analysis. For case study presented here, it is seen that in general, uncertainty in the fatigue strength exponent (m) has the highest impact on fatigue reliability of SCRs. The second most important random variable is the stress range (S), which captures uncertainties in parameters such as loads and material properties. Parametric sensitivity studies on the fatigue strength parameters indicate that SCR reliability is sensitive to both the standard deviation and probability distribution of the parameters, thus highlighting the need for accurate probabilistic calibration of the random variables.

Probabilistic Fatigue Reliability Analysis of Deepwater Steel Catenary Risers

2008 ◽  
Author(s):  
Jie Xia ◽  
Purnendu K. Das
Keyword(s):  
Fatigue Strength ◽  
Probability Distributions ◽  
Water Environment ◽  
Model Parameters ◽  
Fatigue Reliability ◽  
Strength Parameters ◽  
Reliability Method ◽  
Stress Levels ◽  
Damage Indicators ◽  
Steel Catenary Risers

In recent years, offshore reservoirs have been developed in deeper and deeper water environments, where floating production, storage and offloading (FPSO), semi-submersibles, spars and TLPs are considered to be the most economically viable platforms. Steel Catenary Risers (SCRs) are being considered for these production units in deepwater development such as Northern North Sea. A variety of uncertainties are associated with material behaviour, environmental loading, hydromechanics modelling, structural modelling, and fatigue / corrosion / wear characteristics, especially at hang-off and touch down points. To improve the understanding of SCR behaviour and increase the confidence in the design of such systems in deep water environment, a probabilistic reliability-based methodology that systematically accounts for the inherent uncertainties is needed. By using a probabilistic mechanics approach, the existing deterministic design/analysis methods are improved with introduction of uncertainties in model parameters. This paper concentrates on the probability of failure associated with the current design practice of fatigue analysis of SCRs. A probabilistic methodology for fatigue reliability is developed, which utilizes deterministic cumulative fatigue damage indicators calculated from DeepC, namely the stress levels and cycles associated with the various sea states and the fatigue strength of the members. Uncertainties in structural load and material properties are accounted for by assigning probability distributions and standard deviations to the deterministic stress levels. Furthermore, fatigue strength parameters, Miner’s indices, and capacities are modelled as random variables. First order reliability method (FORM) and second order reliability method (SORM) are employed for estimating fatigue reliability. The methodology is applied to two deterministic case studies, involved either a semi-submersible or a FPSO platform. The effect of uncertainties in parameters on fatigue reliabilities is investigated. Additional insight is gained from the parametric sensitivity studies on the fatigue strength parameters.

Rational Stress Limits and Load Factors for Finite Element Analyses in Pipeline Applications: Part III — Elastic-Plastic Load Factor Development

2016 ◽  
Author(s):  
Rhett Dotson ◽  
Chris Alexander ◽  
Ashwin Iyer ◽  
Al Gourlie ◽  
Richard Kania
Keyword(s):  
Finite Element ◽  
Case Studies ◽  
Large Diameter ◽  
Load Factor ◽  
Pipe Material ◽  
Line Pipe ◽  
Elastic Plastic ◽  
First Case ◽  
Load Factors

In this paper, a methodology is presented to develop load factors for use in elastic-plastic assessments of pipelines and their components. The load factors are based on the pipe material properties and the ASME pipeline code’s design margin for the service and location of the pipeline installation [1, 2]. These codes are recognized by 49 CFR 192 and 195 [3, 4]. Minimum required load factors for internal pressure loads can be derived analytically based on design equations from the ASME B31 piping codes and minimum material requirements for API 5L line pipe [6]. Once the load factor is established for a particular case, the elastic-plastic methodology may be used in the Finite Element Analysis (FEA) of pipelines and related components. This methodology is particularly useful in the assessment of existing systems when linear elastic numerical analysis shows that local stresses may exceed the elastic design limits. Two case studies are presented showing analyses performed with Abaqus [5], a commercial, general purpose FEA software package. The first case study provides an assessment of a large diameter elbow where the stress on the outer fibers of the intrados exceeded the longitudinal stress limits from B31.8. The second case study examines an assessment of a tee connection where the stresses on the ID exceeded the yield strength of the component. In addition to the case studies, the paper also presents the results of a full-scale test that demonstrated what margin was present when the numerical calculations were based on specified minimum properties. This paper is not intended to revise or replace any provision of B31.4 and/or B31.8 [1, 2]. Instead, it provides the means for calculating load factors that can be used with an elastic-plastic analysis approach in a manner that provides the same design margins as the ASME B31 codes. The approach described in this paper is intended for use in the detailed FEA of pipelines and their associated components.

scholarly journals Development of Stochastic Fatigue Model of Reinforcement for Reliability of Concrete Structures

2020 ◽  
Vol 10 (2) ◽  
pp. 604 ◽  
Author(s):  
Sima Rastayesh ◽  
Amol Mankar ◽  
John Dalsgaard Sørensen ◽  
Sajjad Bahrebar
Keyword(s):  
Fatigue Strength ◽  
Maximum Likelihood Method ◽  
Stochastic Modelling ◽  
Likelihood Method ◽  
Parameter Estimates ◽  
Statistical Uncertainty ◽  
Fatigue Reliability ◽  
Statistical Parameters ◽  
Composite Bridge

This paper presents recent contributions to the Marie Skłodowska-Curie Innovative Training Network titled INFRASTAR (Innovation and Networking for Fatigue and Reliability Analysis of Structures-Training for Assessment of Risk) in the field of reliability approaches for decision-making for wind turbines and bridges . Stochastic modeling of uncertainties for fatigue strength parameters is an important step as a basis for reliability analyses. In this paper, the Maximum Likelihood Method (MLM) is used for fitting the statistical parameters in a regression model for the fatigue strength of reinforcement bars. Furthermore, application of the Bootstrapping method is investigated. The results indicate that the latter methodology does not work well in the considered case study because of run-out tests within the test data. Moreover, the use of the Bayesian inference with the Markov Chain Monto Carlo approach is studied. These results indicate that a reduction in the statistical uncertainty can be obtained, and thus, better parameter estimates are obtained. The results are used for stochastic modelling in reliability assessment of a case study with a composite bridge. The reduction in statistical uncertainty shows high impact on the fatigue reliability in a case study on the Swiss viaduct Crêt De l’Anneau.

Steel Lazy Wave Risers - A Viable Solution for Turret and Spread Moored FPSOs

2014 ◽  
Author(s):  
Mischa Dylewski ◽  
Vinanti Shah
Keyword(s):  
Large Diameter ◽  
Performance Comparison ◽  
Harsh Environments ◽  
Field Development ◽  
Viable Solution ◽  
Increasing Trend ◽  
Steel Catenary Risers

Floating Storage Production and Offloading (FPSO)host platform selection is an increasing trend due to economic sand versatility offered for field development. The industry is migrating toward more robust riser types to outfit these platforms. Steel Lazy Wave Risers (SLWRs) are an adaptation of Steel Catenary Risers (SCRs) and have been gaining traction in recent years as a viable solution to harsh environments in ultra-deepwater. The following paper will present an overview of the host platforms that could benefit most from use of lazy wave risers and a justification of their application. A case study highlighting the performance comparison of large diameter SCRs versus SLWRs attached to turret and spread moored FPSO platforms in a moderate environment will be presented. The results indicate that SLWRs prove feasible with sufficient margins in strength and fatigue when compared to simple SCRs.

scholarly journals Penerapan Kombinasi Pijat Punggung Dan Dzikir Terhadap Tingkat Stres Pada Penderita Hipertensi Di Desa Seturi Kabupaten Batang

2021 ◽  
Vol 1 ◽  
pp. 621-627
Author(s):  
Riska Yustianika ◽  
Aisyah Dzil Kamalah
Keyword(s):  
Blood Pressure ◽  
Systolic Blood Pressure ◽  
Case Studies ◽  
Massage Therapy ◽  
Pharmacological Therapy ◽  
Stress Levels ◽  
The Subject ◽  
Moderate Stress ◽  
Back Massage

AbstractHipertension is an increase of systolic blood pressure above 140 mmHg and diastolic above 90 mmHg. The patients get dizziness, anxiety, stress, restlessness, weakness, and worry about their health. The purpose of this case study was to determine the application of a combination of back massage and dhikr to stress levels in hypertension sufferers in Seturi Village, Batang Regency. The method used in this paper was a case study with the subject of two axienty clients. The focus of the intervention was providing non-pharmacological therapy, relaxcation, back massage and dhikr for 3 visits to the client’s home. The result of the case studies on these two client’s showed a change in the level of stress on hypertension reduced in client I from TD : 160/100 mmHg down to 140/90 mmHg, PSS-10 : Score 14 (moderate stress) to 0 (no stress), moderate client II from TD : 170/100 mmHg down to 140/90 mmHg, PSS-10 : Score 26 (moderate stress) to 0 (no stress). Therefore, it can be concluded that there is an effect of back massage therapy and dhikr on stress stress levels in patients with hypertension. There is also stress levels in patiens with hypertension.Keywords : Dhikir; Clients With Hipertension; Back Massage And Stress AbstrakHipertensi adalah peningkatan tekanan darah sistolik berada diatas 140 mmHg dan diastolik diatas 90 mmHg. Keluhan yang dirasakan adalah pusing, cemas, stress, gelisah, lemas, dan khawatir terhadap penyakitnya. Tujuan studi kasus ini adalah untuk mengetahui penerapan kombinasi pijat punggung dan dzikir terhadap tingkat stress pada penderita hipertensi di Desa Seturi Kabupaten Batang. Metode studi kasus ini adalah studi kasusdengan subyek dua klien ansietas. Fokus intervensi berupa pemberian terapi non farmakologi relaksasi pijat punggung dan dzikir selama 3 kali kunjungan kerumah klien. Hasil studi kasus pada kedua klien ini menunjukkan adanya perubahan tingkat stress terhadap hipertensipada kedua klien ini menunjukkan adanya perubahan tingkat stress terhadap hipertensi berkurang pada klien I dari TD : 160/100 mmHg turun menjadi 140/90 mmHg, PSS-10 : Skore 14 (stress sedang) menjadi 0 (tidak stress), sedang klien II dari TD : 170/100 mmHg turun menjadi 140/90 mmHg, PSS-10 : Skore 26 (stress sedang) menjadi 0 (tidak stress). Kesimpulan : Ada pengaruh terapi pijat punggung dan dzikir terhadap tingkat stress pada penderita hipertensi. Berdasarkan hasil penerapan tersebut maka disarankan peran perawatdapat memberikan terapi pijat punggung dan dzikir untuk menurunkan tingkat stress pada penderita hipertensi.Kata kunci : Dzikir; Klien Dengan Hipertensi; Pijat Punggung Dan Stress.

A Case Study of Predicting Tensile Strain Capacity of In-Service Pipelines

2020 ◽  
Author(s):  
Junfang Lu ◽  
Ali Fathi ◽  
Nader Yoosef-Ghodsi ◽  
Debra Tetteh-Wayoe ◽  
Mike Hill
Keyword(s):  
Material Properties ◽  
Tensile Strain ◽  
Large Diameter ◽  
Ground Movement ◽  
Capacity Assessment ◽  
Pipe Material ◽  
Strain Capacity ◽  
Welding Processes ◽  
Tensile Strain Capacity

Abstract Strain-based design (SBD) method has evolved over the years for use in the construction of large-diameter, high pressure gas and liquid transmission pipelines. It has not been widely materialized for major construction projects because of the technical complexity which requires multidisciplinary expertise including, but not limited to, pipeline material properties, welding processes, mechanical testing, field construction, and weld inspection. The industry has been showing more interest in using this methodology for strain capacity assessment of in-service stress-based pipelines, especially those that are subjected to ground movement. The strain capacity assessment of the stress-based pipelines is essential to ensure structural integrity and operational safety of the pipeline. This has become more apparent due to recent incidents in pipeline industry caused by geotechnical hazards. This paper provides a case study of assessing the tensile strain capacity (TSC) of existing modern linepipes manufactured through thermomechanical controlled process (TMCP). The TSC was predicted using two main methodologies in the public domain: the CSA Z662-11 Annex C approach and the PRCI-CRES TSC model. Actual pipeline information and construction data are used to perform TSC assessment when possible. This includes pipe material properties, welding procedures qualified on the project pipe, and test weld properties. The predicted TSC and the estimated strain demand will allow for effective remediation decisions. This work helps to enhance pipeline strain management systems in response to the geotechnical and hydrotechnical issues and therefore fills the gaps in present day’s pipeline threat management programs in addition to crack, corrosion and mechanical damage threats. Through such a program, prevention, monitoring and mitigation strategies can be deployed to existing stress-based pipelines, especially in areas where pipeline strain is identified as a potential risk.

Patientenbezogene Komplexität in der Pflege – Kollektive Case Studies im Akutspital

Pflege ◽  
2018 ◽  
Vol 31 (5) ◽  
pp. 237-244 ◽  
Author(s):  
Caroline Gurtner ◽  
Rebecca Spirig ◽  
Diana Staudacher ◽  
Evelyn Huber
Keyword(s):  
Case Studies ◽  
Study Designs

Zusammenfassung. Hintergrund: Die patientenbezogene Komplexität der Pflege ist durch die Merkmale „Instabilität“, „Unsicherheit“ und „Variabilität“ definiert. Aufgrund der reduzierten Aufenthaltsdauer und der steigenden Zahl chronisch und mehrfach erkrankter Personen erhöht sich die Komplexität der Pflege. Ziel: In dieser Studie untersuchten wir das Phänomen patientenbezogener Komplexität aus Sicht von Pflegefachpersonen und Pflegeexpertinnen im Akutspital. Methode: Im Rahmen eines kollektiven Case-Study-Designs schätzten Pflegefachpersonen und Pflegeexpertinnen die Komplexität von Pflegesituationen mit einem Fragebogen ein. Danach befragten wir sie in Einzelinterviews zu ihrer Einschätzung. Mittels Within-Case-Analyse verdichteten wir die Daten induktiv zu Fallgeschichten. In der Cross-Case-Analyse verglichen wir die Fallgeschichten hinsichtlich deduktiv abgeleiteter Merkmale. Ergebnisse: Die Ausprägung der Komplexität hing in den vier Cases im Wesentlichen davon ab, ob klinische Probleme kontrollierbar und prognostizierbar waren. Je nach individuellen Ressourcen der Patientinnen und Patienten stieg bzw. sank die Komplexität. Schlussfolgerungen: Komplexe Patientensituationen fordern von Pflegefachpersonen Fachwissen, Erfahrung, kommunikative Kompetenzen sowie die Fähigkeit zur Reflexion. Berufsanfänger und Berufsanfängerinnen werden zur Entwicklung dieser Fähigkeiten idealerweise durch erfahrene Berufskolleginnen oder -kollegen unterstützt und beraten.

SenCity – Evaluating Users’ Experiences of Intelligent Lighting for Well-Being in Smart Cities

2018 ◽  
pp. 60-67
Author(s):  
Henrika Pihlajaniemi ◽  
Anna Luusua ◽  
Eveliina Juntunen
Keyword(s):  
Case Studies ◽  
Smart City ◽  
Smart Cities ◽  
Well Being ◽  
Evaluation Methods ◽  
Data Analyses ◽  
Sense Of Security ◽  
System Data

This paper presents the evaluation of usersХ experiences in three intelligent lighting pilots in Finland. Two of the case studies are related to the use of intelligent lighting in different kinds of traffic areas, having emphasis on aspects of visibility, traffic and movement safety, and sense of security. The last case study presents a more complex view to the experience of intelligent lighting in smart city contexts. The evaluation methods, tailored to each pilot context, include questionnaires, an urban dashboard, in-situ interviews and observations, evaluation probes, and system data analyses. The applicability of the selected and tested methods is discussed reflecting the process and achieved results.

Nonwovens: Global Trends in World Economy, European Foreign Trade, and Selected Case Studies from Poland and Asian Brics Countries

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Zofia Wysokińska ◽  
Tomasz Czajkowski ◽  
Katarzyna Grabowska
Keyword(s):  
Case Studies ◽  
World Economy ◽  
World Market ◽  
Global Trends ◽  
Textile Materials ◽  
Brics Countries ◽  
Recent Trends ◽  
Almost All ◽  
Special Case

AbstractNonwovens are one of the most versatile textile materials and have become increasingly popular in almost all sectors of the economy due to their low manufacturing costs and unique properties. In the next few years, the world market of nonwovens is predicted to grow by 7%–8% annually (International Nonwovens & Disposables Association [INDA], European Disposables and Nonwovens Association [EDANA], and Markets and Markets). This article aims to analyze the most recent trends in the global export and import of nonwovens, to present two case studies of Polish companies that produce them, and to present one special case study of the market of nonwoven geotextiles in China and India, which are the Asian transition economies among the BRICS countries (Brazil, Russia, India, China, and South Africa).

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