Re-Evaluation of Suction Anchor Holding Capacity Based on Back Analysis of Undrained Shear Strength

2016 ◽  
Author(s):  
Yunsup Shin ◽  
Thomas Langford ◽  
Jerome De Sordi
Keyword(s):  
Back Analysis ◽  
Original Design ◽  
Storage Unit ◽  
Norwegian Sea ◽  
Floating Structures ◽  
Offshore Installations ◽  
Operational Lifetime ◽  
Geotechnical Design ◽  
Anchor Systems ◽  
Work Done

Suction anchors are used within mooring systems for a range of deep water floating structures. The number of suction anchor systems has increased rapidly over the last two decades due to ease of installation and a well-defined design approach. As with other offshore installations, anchor systems may be subjected to re-assessment during their operational lifetime, due to changes in loading, codes or other issues. Such assessment was performed recently for a floating storage unit (FSU) presently in service in the Norwegian Sea, where the geotechnical design of the anchors was re-evaluated. The re-assessment of this storage unit allowed for a number of changes compared to the original design, including updated loads and load histories as well as changes to the safety factors. The geotechnical aspects of the design were also updated, including more refined analyses and a detailed review of the design soil profiles based on back-analysis of installation data. This paper presents the work done related to the geotechnical holding capacity of the anchors during the assessment project. The work performed highlights the benefit of efficient FE analysis and a thorough evaluation of the soil properties and engineering behaviour.

A Framework for the Management of Ageing of Safety Critical Elements Offshore

2011 ◽  
Author(s):  
John V. Sharp ◽  
Edmund G. Terry ◽  
John Wintle
Keyword(s):  
Life Extension ◽  
Original Design ◽  
Safety Critical ◽  
Critical Elements ◽  
The North ◽  
Design Life ◽  
Offshore Installations ◽  
Management Processes ◽  
The North Sea ◽  
And Performance

Many offshore installations in the North Sea have now exceeded their original design life and are in a life extension phase. A Framework of six processes has been developed for the management of ageing of Safety Critical Elements (SCEs) in offshore installations. The processes include an analysis of the effect of ageing modes on SCE performance. Examples of performance indicators for typical SCEs are proposed based on how their condition and performance as may be affected by physical deterioration and other effects of ageing. Indicators for calibrating the maturity and effectiveness of the management processes are also suggested.

Risk Assessment and Management for Geotechnical Design of Offshore Installations

2019 ◽  
Author(s):  
Suzanne Lacasse ◽  
Farrokh Nadim ◽  
Noel Boylan ◽  
Zhongqiang Liu ◽  
Young Jae Choi
Keyword(s):  
Risk Assessment ◽  
Offshore Installations ◽  
Geotechnical Design ◽  
Risk Assessment And Management

Hull Structure Integrity Management in Floating Structures–FSO Puteri Dulang Case

2014 ◽  
Vol 69 (7) ◽  
Author(s):  
Ajith Kumar Thankappan ◽  
M. Fazli B. M. Yusof
Keyword(s):  
Fatigue Life ◽  
Structural Integrity ◽  
Structural Response ◽  
Offshore Structures ◽  
Design Phase ◽  
Floating Structures ◽  
Offshore Installations ◽  
Hull Structure ◽  
Integrity Management ◽  
New Buildings

This paper highlights the key differences in practices employed in managing hull structure integrity of permanently moored floating offshore structures as against sailing vessels which are subject to periodic dry docking. During the design phase, the structural integrity management over the life of a sailing vessel is primarily taken into account by means of Class prescribed Nominal Design Corrosion Values which are added to minimum scantling requirements calculated based on strength and fatigue criteria. In contrast, for permanently moored offshore installations like FPSOs, FSOs etc. the hull structure integrity over the entire design life of the asset is a key design consideration both for new buildings and conversions. Analytic methods and tools (primarily those developed by Class Societies) are available to evaluate the strength requirements (based on yielding, buckling and ultimate strength criteria) and fatigue life of the hull structure. Typically three levels of analysis with increasing degree of complexity and analysis time are used to predict the structural response and fatigue life of the Hull during design phase. The degree of detailed analysis required needs to be determined in light of the expected optimization in terms of savings in scantlings for new building or for steel renewal requirements in case of conversions.

scholarly journals RESEARCH OF THE WAVE FACTOR INFLUENCING HYDRAULIC STRUCTURES

2021 ◽  
Vol 05 (01) ◽  
pp. 81
Author(s):  
Sevda Aliyeva ◽  
Mahmud Ismayilov
Keyword(s):  
Wind Pressure ◽  
Horizontal Wind ◽  
Hydraulic Structures ◽  
Wave Loads ◽  
Floating Structures ◽  
Wave Pressure ◽  
Oil Platforms ◽  
Offshore Installations ◽  
Horizontal Wave ◽  
Design Characteristics

It is known that a large block of deep-sea foundations consists of a truss sheathed with wood, a metal beam system, floating structures and four pyramidal metal blocks with a truss structure. The design characteristics of the foundations of oil platforms depend on the conditions under which the vertical interaction, along with the calculation of permanent and temporary loads, is accompanied by the specific gravity of drilling equipment and rigs or horizontal wind pressure, as well as the influence of horizontal wave loads on the foundation blocks. Horizontal waves and wind loads can be constant and variable in different conditions, therefore the effect of each of these loads on the device must be considered separately. To determine the wave pressure acting on the support blocks of stationary offshore installations, SN-92-60 was used under the editorship of the team of authors under the leadership of Doctor of Technical Sciences, Professor N.N.Tsunkov. Keywords: hydraulic structures, wave factor, wave pressure, wave profile, pressure diagrams, 3D model.

Experiences Gained During the Development of the License Renewal Application for Unit 1 of Paks NPP

2012 ◽  
Author(s):  
Sandor Ratkai ◽  
Tamas Janos Katona
Keyword(s):  
Atomic Energy ◽  
Original Design ◽  
Term Operation ◽  
Atomic Energy Authority ◽  
Operational Lifetime ◽  
License Renewal

Operational license of the four VVER-440/213 units at Paks NPP, Hungary is limited to the design lifetime of 30 years. Extension by an additional 20 years of the original license is one of the main goals of the plant owner. In 2008 a programme for long-term operation (LTO) was developed and submitted to the Hungarian Atomic Energy Authority. The LTO Programme defines the activities for ensuring the extension of the operational lifetime and contains the justification of the safe LTO. The LTO Programme has to be implemented and comprehensive justification of the safe LTO has to be provided in the formal License Renewal Applications unit by unit. This work has been completed by the end of 2011, and the application has been submitted for approval for the Unit 1. The authority review and the approval of the License Renewal Application for Unit 1 should be finished before the expiration of the original design lifetime in 2012. In line with the regulations and supporting the License Renewal Application, a large number of engineering tasks have been performed. In this paper the entire project will be reported. The issues will be discussed, which have been arisen during the development of the application as well as the difficulties generated by the Hungarian technical and regulatory peculiarities will be presented.

Fatigue Life Extension of Offshore Structures by Ultrasonic Peening

2011 ◽  
Author(s):  
Luis Lopez Martinez
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Fatigue Resistance ◽  
Structural Integrity ◽  
High Stress ◽  
Offshore Structures ◽  
Life Extension ◽  
Original Design ◽  
Ultrasonic Peening ◽  
Offshore Installations

The service life of offshore installations is limited by its structural integrity. Furthermore the structural integrity is mainly governed by the fatigue resistance of critical welded details. In a FPSO installation these details are among others pallet stools weld joints to deck structure and bulkheads/web frames weld connections to longitudinal in ballast tanks. ultrasonic peening can improve the fatigue resistance of welded joints. Fatigue test results shows an increase of four times for high stress ranges and up to ten times for high cycle fatigue. For specimens which have already consumed half of their fatigue life the treatment resets the clock to zero, as a minimum value. Consequently ultrasonic peening treatment was applied to several offshore installations on fatigue sensitive weld connections with the objective to extend the service life of the these. Finite Element Analysis carried out by classification societies for these offshore structures demonstrated critical fatigue lives for several weld connections. These weld connections were then treated by ultrasonic peening with the objective to extend their fatigue lives and by doing that reach the targeted service life for the installation. The successful application of the ultrasonic peening treatment was a pioneering work which involved several partners. A pilot project on a FPSO started in 2005 and the treated critical weld connections are still intact and show not sign of crack initiation despite the fact the calculations then showed shorter fatigue lives than the life span already consumed. As a result the same ultrasonic peening procedure has been proposed to be applied for other fatigue sensitive locations on the installation. Offshore installations around the world are reaching their original design life. Most of the operators chose to extend the service life of their assets rather than scrape them and build new. The reasons for that are: improved oil recovering techniques, time required to get a new build installation on site, environment concerns, wiser management of energy and resources among others. Therefore the Life Extension of Offshore Installations is a subject of current interest for the upstream industry.

State of Art in Life Extension of Existing Offshore Structures

2012 ◽  
Author(s):  
Abe Nezamian ◽  
Robert J. Nicolson ◽  
Dorel Iosif
Keyword(s):  
Structural Integrity ◽  
Oil And Gas ◽  
Offshore Structures ◽  
Life Extension ◽  
Operational Environment ◽  
Original Design ◽  
Safety Level ◽  
Operational Conditions ◽  
Offshore Installations ◽  
State Of Art

A large number of the old oil and gas facilities have reached or exceeded their initial design life. With a continued requirement to produce oil or gas, either from the original fields or as a base for neighbouring subsea completions, many of these respective offshore installations are likely to remain operational for a period of time in the foreseeable future. The ageing offshore infrastructure presents a constant and growing challenge. Ageing is characterised by deterioration, change in operational conditions or accidental damages which, in the severe operational environment offshore, can be significant with serious consequences for installation integrity if not managed adequately and efficiently. In order to ensure technical and operational integrity of these ageing facilities, the fitness for service of these offshore structures should be maintained. The maintenance of structural integrity is a significant consideration in the safety management and life extension of offshore installations. Detailed integrity assessments are needed to demonstrate that there is sufficient technical, operational and organisational integrity to continue safe operation throughout a life extension. Information on history, characteristic data, condition data and inspection results are required to assess the current state and to predict the future state of the facility and the possible life extension. This paper presents state of art practices in life extension of existing offshore structures and an overview of various aspects of ageing related to offshore facilities, represented risk to the integrity of a facility and the required procedures and re assessment criteria for deciding on life extension. This paper also provides an overall view in the structural requirements, justifications and calibrations of the original design for the life extension to maintain the safety level by means of a maintenance and inspection programs balancing the ageing mechanisms and improving the reliability of assessment results.

Life Extension Issues for Ageing Offshore Installations

2008 ◽  
Author(s):  
A. Stacey ◽  
M. Birkinshaw ◽  
J. V. Sharp
Keyword(s):  
Structural Integrity ◽  
Life Extension ◽  
Original Design ◽  
The North ◽  
Design Life ◽  
Offshore Installations ◽  
Need To Evaluate ◽  
Integrity Management ◽  
The North Sea ◽  
The Uk

With many offshore installations in the UK sector of the North Sea now reaching or being in excess of their original anticipated design life, there is a particular need to evaluate approaches to structural integrity management by offshore operators. Ageing processes can affect the structural integrity of the installation and demonstration of adequate performance beyond its original design life is thus a necessary requirement. This paper addresses the issues relevant to the life extension of ageing installations.

Influence of Wave-Induced Skid Motions on the Launch of Free-Fall Skid Lifeboats From Floating Hosts: Experimental and Numerical Investigations

2014 ◽  
Author(s):  
Neil Luxcey ◽  
Svein-Arne Reinholdtsen ◽  
Thomas Sauder ◽  
Sébastien Fouques ◽  
Jingzhe Jin ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Model Test ◽  
Degrees Of Freedom ◽  
Free Fall ◽  
Weather Conditions ◽  
Norwegian Sea ◽  
Six Degrees Of Freedom ◽  
Offshore Installations ◽  
Storm Condition ◽  
Wave Induced

The evacuation of personnel from offshore installations in severe weather conditions is generally ensured by free-fall lifeboats. Their performance can be assessed by means of numerical simulations to estimate accelerations loads on occupants, structural loads on the lifeboat hull, as well as forward speed after water-exit. These parameters strongly depend on the water entry conditions of the lifeboat, which in turn are very sensitive to the previous phases of the launch that starts on the skid. On floating production, storage and offloading (FPSO) vessels in the Norwegian Sea, lifeboats are often installed on skids at the bow so that waves may induce large skid motions with typical extreme vertical amplitude of fifteen to twenty meters in a 100-year storm condition. Moreover, wave-induced motions may also cause trim and list of the skid, which initiates more complex six degrees-of-freedom trajectories during free-fall. In such conditions, a proper modelling of the lifeboat trajectory on the moving skid is necessary in order to assess the performance of the lifeboat with numerical simulations. This paper investigates the effects of the wave-induced skid motion on the launch of free-fall lifeboats from floating hosts. The first part of the paper describes the six-degrees-of-freedom numerical skid model used in MARINTEK’s lifeboat launch simulator VARUNA. The second part presents two model test campaigns aimed at validating the numerical skid model. The model test results are compared to those obtained from the numerical simulations. Finally, the importance of the skid motion on the lifeboat trajectory is discussed.

Social Cognition in Gilles de la Tourette Syndrome

2019 ◽  
Vol 30 (4) ◽  
pp. 243-249
Author(s):  
Ronja Weiblen ◽  
Melanie Jonas ◽  
Sören Krach ◽  
Ulrike M. Krämer
Keyword(s):  
Tourette Syndrome ◽  
Social Cognitive ◽  
Mirror Neuron System ◽  
Mirror Neuron ◽  
Theoretical Work ◽  
Neural Processes ◽  
The Social ◽  
Decision Making System ◽  
Social Decision Making ◽  
Work Done

Abstract. Research on the neural mechanisms underlying Gilles de la Tourette syndrome (GTS) has mostly concentrated on abnormalities in basal ganglia circuits. Recent alternative accounts, however, focused more on social and affective aspects. Individuals with GTS show peculiarities in their social and affective domain, including echophenomena, coprolalia, and nonobscene socially inappropriate behavior. This article reviews the experimental and theoretical work done on the social symptoms of GTS. We discuss the role of different social cognitive and affective functions and associated brain networks, namely, the social-decision-making system, theory-of-mind functions, and the so-called “mirror-neuron” system. Although GTS affects social interactions in many ways, and although the syndrome includes aberrant social behavior, the underlying cognitive, affective, and neural processes remain to be investigated.

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