Assessment of Offshore Platforms Under Subsidence—Part I: Approach

2000 ◽  
Vol 122 (4) ◽  
pp. 260-266 ◽  
Author(s):  
Joseph M. Gebara ◽  
Dan Dolan ◽  
Stuart Pawsey ◽  
Philippe Jeanjean ◽  
Knut Dahl-Stamnes
Keyword(s):  
Structural Integrity ◽  
Soil Mechanics ◽  
Strength Analysis ◽  
Assessment Procedure ◽  
Offshore Platforms ◽  
Acceptance Criteria ◽  
Reliability Modeling ◽  
Systematic Assessment ◽  
International Conference ◽  
Increased Risk

This is the first of four companion papers that present a comprehensive assessment of the effect of sea floor subsidence on the Valhall complex of platforms. The study has included an estimate of the increase in platform failure probability as a function of increased subsidence. Subsidence raises the effective mean still water level and increases the potential for inundation of the deck for extreme storm conditions. Deck wave slam forces generate significantly greater platform loading and lead to: (a) higher levels of structural inelastic response and increased risk of structural failure as well as (b) water reaching the cellar deck, and hence affecting operators as well as equipment. The paper focuses on addressing the first of these two issues. A structural assessment study was performed to address the significance of present and future levels of subsidence on the safety of three North Sea platforms. The study included a systematic assessment procedure that addressed each of the factors that impacted structural integrity issues and reliability concerns. Such factors included: ultimate strength analysis methodologies, tubular joint formulations, group pile effects, and soil-structure interaction, which are described in this paper, as well as deck impact force formulations (Pawsey et al., 1998, “Characterization of Environmental Loads on Subsiding Offshore Platforms,” 17th International Conference on Offshore Mechanics and Arctic Engineering, Lisbon, Portugal, July) component and system reliability modeling (Jha et al., 2000, “Assessment of Offshore Platforms Under Subsidence—Part II: Analysis and Results,” ASME J. Offshore Mech. Arct. Eng., 122, pp. 267–273), and acceptance criteria (Stahl et al., 1998, “Acceptance Criteria for Offshore Platforms,” 17th International Conference on Offshore Mechanics and Arctic Engineering, Lisbon, Portugal, July). This paper presents the assessment procedure, as well as the modeling approach. The paper also discusses the consequence classification of the three platforms and state-of-the-art soil mechanics techniques that lead to a significant increase in the tensile capacity of the foundation. [S0892-7219(00)00204-1]

ECA of Pipeline With Girth Weld Strength Mis-Matching Subjected to Large Strain

2009 ◽  
Author(s):  
Zhengmao Yang ◽  
Shashi Kumar ◽  
Jens P. Tronskar
Keyword(s):  
Base Metal ◽  
Structural Integrity ◽  
Oil And Gas ◽  
Large Strain ◽  
Axial Strain ◽  
Weld Strength ◽  
Assessment Procedure ◽  
Long Distance ◽  
Acceptance Criteria ◽  
Gas Field

In recent years, the strain based design for pipeline has been widely accepted by the industry, but the definition of a rational flaw acceptance criteria for girth welds subjected to axial strain within the context of the existing codified fracture mechanics based assessment procedures is problematic since these are essentially stress based. To extend the FAD method to the large strain conditions, several challenges i.e. weld strength mismatching, fracture toughness, and welding residual stresses have to be understood. With appropriate modifications as per DNV-RP-F108 [1], the assessments procedure detailed in BS7910 document for stress based situations have been used successfully for several projects to develop acceptance criteria for pipeline installation involving plastic straining. But only weld metal strength over-match comparing with base metal is considered in DNV-RP-F108 [1]. High strength line pipes are required to reduce the transmission cost of natural gas in long distance and internal clad with corrosion resistant alloy (CRA) is used for transportation of sour gas. Steel manufactures have developed such line pipes to develop new oil and gas field. The inconel filler metal was selected as weld consumable for the production girth weld in the lay budge. From the all weld tensile tests, it was found that the yield strength of the weld is under-match comparing the base metal, and the pipeline maybe subjected to a strain level up to 1.0% due to the lateral buckling. In this research the effect of weld strength mismatching on the structural integrity of the pipeline subjected to large strain was studied. The Engineering Critical Assessment (ECA) was performed to derive the critical flaw acceptance criteria for the AUT system. The segment tests and numerical analysis were performed to validate the assessment procedure, and the finite element analyses of the pipeline girth weld with surface crack in the weld centre were carried out to investigate the effect of bi-axial loading on the ECA results.

Managing Structural Integrity of Offshore Platforms: Looking Back to Drive the Future

2013 ◽  
Author(s):  
Roberto Piva ◽  
Margherita Latronico ◽  
Andrea Nero ◽  
Stefano Sartirana
Keyword(s):  
Structural Integrity ◽  
Offshore Platforms ◽  
The Future ◽  
Looking Back

Structural Integrity for Nuclear Power Plant Against Excessive Load on Design Extension Condition

2013 ◽  
Author(s):  
Daigo Watanabe ◽  
Kiminobu Hojo
Keyword(s):  
Nuclear Power ◽  
Structural Integrity ◽  
Safety Factors ◽  
Design Code ◽  
Acceptance Criteria ◽  
Integrity Assessment ◽  
Current Design ◽  
Factor Design ◽  
Excessive Load ◽  
Load And Resistance Factor

This paper introduces an example of structural integrity evaluation for Light Water Reactor (LWR) against excessive loads on the Design Extension Condition (DEC). In order to assess the design acceptance level of DEC, three acceptance criteria which are the stress basis limit of the current design code, the strain basis limit of the current design code and the strain basis limit by using Load and Resistance Factor Design (LRFD) method were applied. As a result the allowable stress was increased by changing the acceptance criteria from the stress basis limit to the strain basis limit. It is shown that the practical margin of the LWR’s components still keeps even on DEC by introducing an appropriate criterion for integrity assessment and safety factors.

Fracture Assessment of Flaws in Weldments using FITNET FFS Procedure: An Overview

2007 ◽  
Vol 345-346 ◽  
pp. 401-409 ◽  
Author(s):  
Mustafa Koçak ◽  
Stephen Webster ◽  
Isabel Hadley
Keyword(s):  
European Community ◽  
Structural Integrity ◽  
Assessment Procedure ◽  
Metallic Structures ◽  
Fracture Assessment ◽  
Basic Equations ◽  
Network Project

Recently a European community funded thematic network project (participation of 17 countries) FITNET (www.eurofitnet.org) has completed a new and unified engineering assessment procedure (FITNET FFS Procedure) of flaws in metallic structures and welds. This newly developed procedure (under CEN Workshop Agreement WA22) provides assessment rules for flaws or damage due to fracture, fatigue, creep and corrosion to demonstrate the structural integrity of the component. This paper gives an overview of the FITNET Fitness-for-Service (FFS) Procedure and specifically presents the features and basic equations of the Fracture Module. It also presents two brief examples for the validation of the procedure using laser welded specimens.

3. Standardized assessment of the needs for care in a cohort of patients with schizophrenic psychoses

1991 ◽  
Vol 19 ◽  
pp. 27-33 ◽  
Author(s):  
A. D. Lesage ◽  
G. Mignolli ◽  
C. Faccincani ◽  
M. Tansella
Keyword(s):  
Psychiatric Patients ◽  
Social Performance ◽  
Standardized Assessment ◽  
Assessment Procedure ◽  
Systematic Assessment ◽  
Needs For Care ◽  
Psychiatric Case ◽  
The Social

There is a well-established tradition in standardized evaluation of the symptomatology and the social performance of psychiatric patients (Wing et al. 1974; WHO, 1983b; Platt, 1983) together with instruments for describing the pattern of contacts with services, like Psychiatric Case Registers (Wing & Hailey, 1972; ten Horn et al. 1986). Interest in a systematic assessment procedure for recording which action should be taken by services in the presence of a problem is more recent. Instruments for these evaluations are still experimental.

RISK-BASED MANAGEMENT OF STRUCTURAL INTEGRITY FOR BASS STRAIT PLATFORMS

2001 ◽  
Vol 41 (1) ◽  
pp. 727
Author(s):  
A.D. Barton
Keyword(s):  
Structural Integrity ◽  
Risk Model ◽  
Offshore Platforms ◽  
Integrity Assessment ◽  
Inspection And Maintenance ◽  
Tubular Joint ◽  
Maintenance Activities ◽  
Consistent Basis ◽  
Inspection Data ◽  
Inspection Techniques

Esso Australia Pty Ltd (Esso) has embraced the framework of risk management to improve the focus and priorities of its inspection and maintenance activities. Structural integrity is one of the disciplines that has adopted a risk-based approach to inspection and integrity assessment and this has been applied to Esso/BHP’s 18 offshore platforms located in Bass Strait.The paper provides a discussion of the issues faced in the management of structural integrity of offshore platforms which lead to the development of a risk-based inspection (RBI) strategy. RBI is applied to improve the prediction of the structures’ condition and provides a consistent basis for continued improvement in the future. The RBI model generates targeted inspection workscopes for each platform that, coupled with the implementation of appropriate inspection techniques, ensure that the integrity of the platforms can be managed with greater confidence and at lower cost.The RBI approach has resulted in reduced focus on traditional areas of uncertainty such as fatigue of tubular joints, and increased focus on secondary structures, for example service caissons. This shift in focus is made possible by building into the risk model a calibration process that considers previous inspection data. A key component of this calibration is a new method developed to calibrate tubular joint fatigue lives.

Wave Impact Load and Corresponding Nonlinear Response of a Semi-Submersible

2019 ◽  
Author(s):  
Yinghao Guo ◽  
Longfei Xiao ◽  
Handi Wei ◽  
Lei Li ◽  
Yanfei Deng
Keyword(s):  
Spatial Distribution ◽  
Structural Integrity ◽  
Impact Load ◽  
Wave Crest ◽  
Impulsive Effect ◽  
Offshore Platforms ◽  
Wave Impact ◽  
Global Response ◽  
Local Wave ◽  
Incident Waves

Abstract Offshore platforms operating in harsh ocean environments often suffer from severe wave impacts which threaten the structural integrity and staffs safety. An experimental study was carried out to investigate the wave impact load and its effect on the global response of a semi-submersible. First, two typical wave impact events occurring successively in the wave test run are analyzed, including the characteristics of incident waves, relative wave elevations and the spatial distribution of the wave impact load. Subsequently, the corresponding global response of the semi-submersible under these two wave impacts are investigated in time domain. It reveals that compared with the incident wave, the relative wave elevation has a more straightforward relationship with the wave impact load. The relative wave crest height is associated with the spatial distribution of the wave impact load, while the local wave steepness matters more in the magnitude of the wave impact load. The impulsive effect of the wave impact load on the motion behaviors is not obvious. But severe wave impacts can introduce excessive horizontal accelerations and nonlinear behaviors like ringing in the acceleration response.

Estimation of Through-Wall Cracking Frequency of RPV Under PTS Events Using PFM Analysis Method for Identifying Conservatism Included in Current Japanese Code

2014 ◽  
Author(s):  
Kazuya Osakabe ◽  
Koichi Masaki ◽  
Jinya Katsuyama ◽  
Genshichiro Katsumata ◽  
Kunio Onizawa
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Crack Initiation ◽  
Structural Integrity ◽  
Probabilistic Approach ◽  
Pressure Vessels ◽  
Assessment Procedure ◽  
Analysis Method ◽  
Integrity Assessment ◽  
The U.S

To assess the structural integrity of reactor pressure vessels (RPVs) during pressurized thermal shock (PTS) events, the deterministic fracture mechanics approach prescribed in Japanese code JEAC 4206-2007 [1] has been used in Japan. The structural integrity is judged to be maintained if the stress intensity factor (SIF) at the crack tip during PTS events is smaller than fracture toughness KIc. On the other hand, the application of a probabilistic fracture mechanics (PFM) analysis method for the structural reliability assessment of pressure components has become attractive recently because uncertainties related to influence parameters can be incorporated rationally. A probabilistic approach has already been adopted as the regulation on fracture toughness requirements against PTS events in the U.S. According to the PFM analysis method in the U.S., through-wall cracking frequencies (TWCFs) are estimated taking frequencies of event occurrence and crack arrest after crack initiation into consideration. In this study, in order to identify the conservatism in the current RPV integrity assessment procedure in the code, probabilistic analyses on TWCF have been performed for certain model of RPVs. The result shows that the current assumption in JEAC 4206-2007, that a semi-elliptic axial crack is postulated on the inside surface of RPV wall, is conservative as compared with realistic conditions. Effects of variation of PTS transients on crack initiation frequency and TWCF have been also discussed.

Choline in pregnancy and breastfeeding

2015 ◽  
Author(s):  
Sir Peter Gluckman ◽  
Mark Hanson ◽  
Chong Yap Seng ◽  
Anne Bardsley
Keyword(s):  
Breast Milk ◽  
Structural Integrity ◽  
Cholesterol Transport ◽  
High Demand ◽  
Lactating Women ◽  
Methyl Group ◽  
Neonatal Life ◽  
Increased Risk ◽  
Folate And Vitamin B12 ◽  
In Pregnancy

Choline is required for the structural integrity of cell membranes and is involved in methyl-group metabolism, neurotransmission, transmembrane signalling, and lipid and cholesterol transport and metabolism. Choline is critical during fetal and neonatal life to ensure optimal brain and cognitive development. There is an intersection of the pathways of choline, folate, and vitamin B12 in the formation of methionine from homocysteine. Maternal peri-conceptional deficiency for choline, like folate, is associated with an increased risk of neural tube defects in the offspring. It is recommended that pregnant women do not restrict fat severely from their diets, as choline is derived from the lipid content of food. Strict vegetarian or vegan diets may be low in choline. The high secretion rate of choline into breast milk means that lactating women have a high demand, and multivitamins containing choline may be helpful for both pregnancy and breastfeeding.

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