bluuebunny/crossref_metadata_2025_split huggingface dataset:
Strain Capacity of Girth Welded Joints in HSAW Pipes
Authors: Van Minnebruggen Koen , Hertelé Stijn , De Waele Wim 
Published: October 2017

The general aim of a recently finalized European project, i.e. EU RFCS SBD-Spipe, is to generate specific know-how concerning the development and possible use of spirally welded pipes for demanding applications. The demanding applications relate especially to structural integrity issues, both onshore and offshore, requiring good performance under application of large strains resulting in buckling, collapse and/or tensile loading. The outcome of this project can also be used as technical basis for improving standards and guidelines, that address design and safety of spirally welded pipelines.
The contribution of Ghent University to this project focusses on the aspects of tearing resistance, defect tolerance and strain capacity of girth welded joints subjected to remote axial tensile load. A numerical and experimental approach is used for the assessment of flaw tolerability and strain development upon tensile loading. Spiral pipes of steel grade API-5L X70 with 36” and 48” diameters have been girth welded using both a manual and semi-automatic welding processes. Curved wide plate specimens have been extracted from the pipes and artificial weld defects have been introduced. The specimens have been loaded in tension up to failure at a temperature of −10°C. This paper reports on the experimental result of a series of curved wide plate tests.
Improved Dynamic Structural Modelling for Subsea Power Cables With Bitumen Coated Armour Wires
Authors: Martindale Hugh , Rossiter Steven , Sheldrake Terence , Langdon Richard 
Published: October 2017

This paper presents improved dynamic modelling of subsea power cables using new models for the determination of non-linear cable mechanical properties. The modelling has been developed for cables typically used in offshore wind and for interconnectors, as well as dynamic power umbilicals. The results provide a better simulation of the dynamic response and allow better integration of local and global modelling for determination of stress and fatigue in offshore power cables.
Cable response due to bending is modelled by including non-linear adhesion induced stresses due to a yielding bond between armour wire and neighbouring layers, which captures the effects of temperature and strain rate and provides better representation than purely friction-based modelling especially at low tension. Local armour bending stiffness is included by using average wire strain energy after slip along the strained helical path to determine the armour layer bending stiffness contribution. Mathematical modelling for mechanical properties is verified by sample testing and FEA, to provide a robust method for predicting cable response.
Although dynamic subsea power cables are essentially non-bonded structures there is a certain amount of adhesion within the structure. Previous work has focused on friction-tension based modelling of armour wire-core interaction, that is not appropriate as critical slip curvatures at low tension are understated and full-slip stress distributions do not account for work done against friction during further bending. The principal result of this new approach is the improved determination of lifetime stresses for critical components within the cable structure. Non-linear bend stiffness modelling produces characteristic moment-curvature relations including hysteresis on reversal of bending. These curves provide an improved representation of the onset of slip in the armour wires and allow for the influence of temperature and strain rate on the cable bending stiffness to be included. The bend-stiffness model has been validated against test data both of complete bundles and individual components.
The overall result is a methodology that typically results in increased fatigue life and can reduce the requirement for ancillary products such as ballast/buoyancy and bend stiffeners/restrictors. Additionally, the non-linear, hysteretic response of a cable significantly reduces certain phenomena that are often associated with numerical modelling of cables using a linear bend stiffness. Specifically, a cable catenary attached to a vessel and modelled with a linear bend stiffness will often experience ‘compression waves’ when the vessel is moving in response to wave loading. Use of a non-linear, hysteretic bend stiffness minimises the compression wave phenomenon, giving a much more realistic response and often greatly improving operability windows for offshore operations.
Evaluation of Nonlinear Material Behavior for Offshore Structures Subjected to Accidental Actions
Authors: Storheim Martin , Alsos Hagbart S. , Amdahl Jørgen 
Published: October 2017

Evaluation of the nonlinear structural response of any structure is a challenging task; a range of input parameters are needed, most of which has significant statistical variability and the evaluations require a high degree of craftsmanship. Hence, high demands are set forth both to the analyst and the body in charge of verification of the results. Recent efforts by DNVGL attempts to mitigate this with the second edition of the DNVGL-RP-C208 for determination of nonlinear structural response, in which guidance or requirements are given on many of the challenging aspects.
This paper discuss the various challenges and the direction to which the RP-C208 points compared to published research. Parameters affecting the plastic hardening, strain-rate effects and ductile fracture are discussed separately. Then, the combined effect of the range of assumptions is evaluated to assess the resulting level of safety.
Design Challenges of the Next Generation of All Electric Umbilical Systems
Authors: Deighton Alan , Dobson Alan 
Published: October 2017

Since the first umbilicals were developed and installed to control and preserve subsea equipment they have continued to evolve to ensure effective operation in an increasingly challenging subsea environment. New material technologies, complex analysis tools and umbilical architectures have been developed to ensure umbilical systems operate through-out their service life irrespective of the ambient temperature, fatigue loading, hyperbaric pressure and tensile loads applied.
In more recent years, as the subsea industry adapts to the challenge of reducing CAPEX costs driven by reduced oil prices, the potential cost savings through adapting the subsea processing system to treat processed fluids on the seabed and / or utilising longer step out systems from existing facilities is driving a new step in umbilical evolution.
To support the potential evolution in subsea processing systems, the conventional control umbilical must evolve to incorporate the supply of electrical power and potentially electrical control to replace hydraulic control over long step out distances. This has a significant influence on the design of the umbilical system, introducing several new challenges which need to be addressed through material selection and advanced analysis techniques.
This paper will provide an overview of the potential evolution of the Next Generation All Electric umbilical and outline the design challenges and methods developed to maximise the reliability of the umbilical system.
ECAs: Lifting the Lid of the Black Box
Authors: Cosham Andrew , Macdonald Kenneth A. , Hadley Isabel , Moore Philippa 
Published: October 2017

An engineering critical assessment (ECA) is commonly conducted during the design of a pipeline in order to determine the tolerable sizes for flaws in the girth welds. An ECA is a method for assessing the acceptability of a flaw in a structure, i.e. to demonstrate fitness-for-service. API 579-1/ASME FFS-1 2016 and BS 7910:2013+A1:2015 Incorporating Corrigenda Nos. 1 and 2 give guidance for conducting fitness-for-service assessments of cracks and crack-like flaws. Appendix A of DNV-OS-F101, 2013 provides detailed procedures for evaluation of the fracture limit state of girth welds, based on BS 7910:2005, but prescribes a number of amendments and modifications. API 579-1/ASME FFS-1 and BS 7910:2013 will give similar, but slightly different, results.
An ECA can be something of a black box because of the use of software to conduct the calculations. Software can have the unfortunate side-effect of obscuring the understanding of the calculations. ECAs are also seen as a thing that is very complicated.
In an attempt to lift the lid on the black box that is, or is perceived to be, the ECA, the assessment of circumferentially orientated, surface-breaking crack-like flaw (a planar flaw) in a girth weld is illustrated through a comparison of the relevant stress intensity factor and reference stress solutions in API 579-1/ASME FFS-1 and BS 7910:2013; and through illustrating the effect of the choice of the Level or Option of the assessment, and assumptions made in the assessment with respect to constraint, misalignment, residual stresses, etc. Also illustrated are the implications of defining the fracture toughness in terms of the crack tip opening displacement or J-integral, and of using a single value of fracture toughness, based on the initiation of stable tearing or the first attainment of a maximum force plateau (maximum load), or of using tearing resistance data.
A comparison is also made with the notionally simplified fitness-for-service procedures given in Annex A of API Standard 1104, Annex K of CSA Z662-15, and the EPRG guidelines on the assessment of defects in transmission pipeline girth welds–Revision 2014.
The result is an outline of what might be considered to be good practice for when conducting an ECA during the design of a pipeline.
Calculation of Time-to-Freeze for Liquids in Pipes
Authors: Kvamme Bjarte O. , Peechanatt Jino , Gudmestad Ove T. 
Published: October 2017

In recent years, there has been unprecedented interest shown in the Arctic region by the industry, as it has become increasingly accessible for oil and gas exploration, shipping, and tourism. The decrease in ice extent in the Arctic has renewed the interest in the Northern Sea route, necessitating further research to evaluate the adequacy of the equipment and appliances used on vessels traversing in polar waters. In the oil and gas industry, exploration and production vessels and platforms are highly dependent on the piping facilities for rendering their intended function, and therefore, flow assurance is extremely crucial. If the winterization of pipes is not done properly, this could lead to massive cost overruns due to unplanned production shutdowns or even worse, accidents. A temperature drop between the different areas of the production facilities will change the thermodynamic properties of the fluids, and could cause the processing of the crude oil to become inefficient.
The introduction of the Polar Code by the International Maritime Organization (IMO) attempts to mitigate some of the risks endangering the vessels in polar waters. The Polar Code is scheduled to take effect on 01.01.2017, and applies to all vessels traversing in polar waters. The Polar Code requires that all machinery installations and associated equipment required for the safe operation of ships shall be protected against the effect of freezing and increased viscosity of liquids, and that working liquids shall be maintained in a viscosity range that ensures the operation of the machinery. To account for this, the heat loss of pipes carrying liquid (water for fire extinguishing and hydraulic fluid amongst others) needs to be estimated and mitigating measures must be taken.
In this study, methodology from the refrigeration industry is applied to calculate the estimated time to freeze for liquids in pipes. The methodology is adapted for use in the maritime industry, and results are presented in this study. The methodology used was found to be quite flexible, allowing for the calculation of complex scenarios and shapes, including the effect of varying degrees of insulation on pipes, and can easily be applied for approximating the best suitable method of insulating pipes to ensure flow assurance and maintain fluid properties at desired levels. Tables estimating the time-to-freeze for insulated pipes of different diameters and insulation thicknesses exposed to cross-winds of varying speeds are provided. The methodology is found to have great potential, and should be investigated further with experiments. The objective of the paper is thus to introduce the methodology for cold-climate engineering and use it for practical analysis of realistic estimates of insulated and non-insulated piping.
Reelability and Wall Thickness Optimization of HFI Pipeline Against the Sensitivity of Variation in Mismatch Parameters
Authors: Achani Dasharatha , Andreev Vladimir 
Published: October 2017

High frequency Induction welded (HFW/HFI) linepipe is produced by cold forming from steel strip, bent into pipe and longitudinal seam welded. HFW/HFI linepipe has been attractive due to less expensive, improved lead time and tighter wall thickness tolerances and better control of mechanical properties compared to the seamless.
Typical design drivers for wall thickness optimization of reeled pipeline are geometric and strength mismatch. HFI pipes gained the attention of reeling contactors because of tighter mismatch tolerances of geometry and strength. However, the limitation of wall thickness in producing the larger diameter pipes needs optimized wall thickness considering the sensitivity of the variation in mismatch properties and stress ratio.
The present work is intended to check the capacity of the pipeline against the sensitivity of variation in mismatch parameters. A case study has performed for the reelability of 16” HFW pipe for a selected limiting wall thickness. The different cases of variation in mismatch parameters are considered for the sensitivity check. Finite element (FE) analyses using ABAQUS tool were performed to reel the sections of the pipe joint over the reel hub of the selected installation vessel. The model predictions for axial compressive strain are compared and discussed against the DNV local buckling criterion for displacement control.
Development of Ice Management Tactics and Navigational Simulation of Ice Management Operations on a State-of-the-Art Training Complex
Authors: Kazantsev Mikhail , Karulina Marina , Karulin Evgeny , Proniashkin Aleksander 
Published: October 2017

Ice management is one of the ways to achieve a more efficient operation of marine ice-resistant platforms in winter, to secure oil offloading operations and, if necessary, to support rescue and evacuation operations. Since 2012, Krylov State Research Centre, St. Petersburg, Russia, runs a training complex for navigational simulation of ship movement in ice conditions, developed with participation of TRANSAS, a global leader in the field of marine navigation simulators. The core functional elements of this training complex are the models of interaction between marine technology (ships and platforms) and ice in given water areas. One of the completed Russian Projects, Prirazlomnaya offshore ice-resistant platform, is taken as a case study to illustrate a stage-by-stage process of working out a tactic of ice management near the platform, including:
1) analysis of ice conditions in the area of Prirazlomnoye oil field, with consideration of environmental variability;
2) development of maneuvering procedures for the ice-breaking vessels to ensure safe oil offload to tankers;
3) polishing these maneuvers by means of a training complex;
4) analysis of the real maneuvers performed near the platform.
This approach allowed a deeper understanding of the developed maneuvering layouts for supply vessels, with respect to specific ice conditions and given operational circumstances.
Full-Scale Validation of Axial Carcass Loads in Flexible Pipe Structure From Cyclic Pressure and Temperature
Authors: Kristensen Claus E. , Muren Jan , Gjendal Andreas , Hanssen Erik B. , Melve Bjørn , Sødahl Nils , Engh Bjørn , Søfferud Mario 
Published: October 2017

With basis in field experiences from several carcass axial failures in HT/HP unbonded flexible risers a comprehensive program was initiated to determine the root cause and develop a theoretical framework for prediction of the loads and mechanisms leading to damage initiation and development. The physical understanding, theory, tools and methods were developed in a close cooperation between the field operator Statoil, 4Subsea and DNV GL.
Following the discovery of carcass tearing as a new failure mode in May 2011 substantial work has been put into small- and mid-scale testing together with the establishment of various analysis models to describe the carcass tearing phenomenon. This development and test work has been presented at OMAE-2013/14. Since 2011 substantial work has been put into small- and mid-scale testing together with various analysis models to describe the carcass pull-out phenomenon.
As a final full-scale validation, an onshore fully instrumented test was conducted to assess the accuracy of the carcass tearing models and evaluate variability and uncertainties related to use of the developed tools and methods for risk assessment of similar HT/HP pipes still in operation. The flexible riser used for the test was a full length 830m long pipe recovered after 15 years’ successful operation at a North Sea Field. The pipe integrity was not jeopardized and the pipe was fully functional at the time of recovery.
The pipe was recovered due to unfavorable risk assessment and plans for full-scale testing. The full-scale test gathers as many aspects as possible into a single test to verify the analytical solutions proposed during this work. The test pipe was used with the original end-fittings with the full pipe length intact. The end sections of length were unreeled, secured, protected and supported.
As preparation to the test, finite element analyses of the flexible riser were performed to predict the carcass axial load in the end-fitting. The analysis also served as valuable input to the test procedure and instrumentation plan. Along with analyses, a set of novel measurement and instrument solutions were developed. This includes, live video monitoring of carcass movements and strain measurements at carcass, with temperature and pressure well outside standard solutions. Bore temperature and pressure varied from 0–90 °C and 0–500 barg, respectively.
Several temperature and pressure cycles were done. Comparison between detailed finite element analysis and full-scale results shows excellent correlation. The riser and end-fittings have been dissected after testing. Key findings from dissection match the predicted behavior well.
Effective Power and Speed Loss of Underwater Vehicles in Close Proximity to Regular Waves
Authors: Daum Stefan , Greve Martin , Skejic Renato 
Published: October 2017

The present study is focused on performance issues of underwater vehicles near the free surface and gives insight into the analysis of a speed loss in regular deep water waves. Predictions of the speed loss are based on the evaluation of the total resistance and effective power in calm water and preselected regular wave fields w.r.t. the non-dimensional wave to body length ratio. It has been assumed that the water is sufficiently deep and that the vehicle is operating in a range of small to moderate Froude numbers by moving forward on a straight-line course with a defined encounter angle of incident regular waves.
A modified version of the Doctors & Days [1] method as presented in Skejic and Jullumstrø [2] is used for the determination of the total resistance and consequently the effective power. In particular, the wave-making resistance is estimated by using different approaches covering simplified methods, i.e. Michell’s thin ship theory with the inclusion of viscosity effects Tuck [3] and Lazauskas [4] as well as boundary element methods, i.e. 3D Rankine source calculations according to Hess and Smith [5]. These methods are based on the linear potential fluid flow and are compared to fully viscous finite volume methods for selected geometries.
The wave resistance models are verified and validated by published data of a prolate spheroid and one appropriate axisymmetric submarine model. Added resistance in regular deep water waves is obtained through evaluation of the surge mean second-order wave load. For this purpose, two different theoretical models based on potential flow theory are used: Loukakis and Sclavounos [6] and Salvesen et. al. [7]. The considered theories cover the whole range of important wavelengths for an underwater vehicle advancing in close proximity to the free surface. Comparisons between the outlined wave load theories and available theoretical and experimental data were carried out for a submerged submarine and a horizontal cylinder.
Finally, the effective power and speed loss are discussed from a submarine operational point of view where the mentioned parameters directly influence mission requirements in a seaway.
All presented results are carried out from the perspective of accuracy and efficiency within common engineering practice. By concluding current investigations in regular waves an outlook will be drawn to the application of advancing underwater vehicles in more realistic sea conditions.
On the Distribution of Wave Impact Loads on Offshore Structures
Authors: Johannessen Thomas B. , Lande Øystein , Hagen Øistein 
Published: October 2017

For offshore structures in harsh environments, horizontal wave impact loads should be taken into account in design. Shafts on GBS structures, and columns on semisubmersibles and TLPs are exposed to impact loads. Furthermore, if the crest height exceeds the available freeboard, the deck may also be exposed to wave impact loads.
Horizontal loads due to waves impacting on the structure are difficult to quantify. The loads are highly intermittent, difficult to reproduce in model tests, have a very short duration and can be very large. It is difficult to calculate these loads accurately and the statistical challenges associated with estimating a value with a prescribed annual probability of occurrence are formidable.
Although the accurate calculation of crest elevation in front of the structure is a significant challenge, industry has considerable experience in handling this problem and the analysis results are usually in good agreement with model test results. The present paper presents a statistical model for the distribution of horizontal slamming pressures conditional on the incident crest height upwave of the structure.
The impact load distribution is found empirically from a large database of model test results where the wave impact load was measured simultaneously at a large number of panels together with the incident crest elevation. The model test was carried out on a circular surface piercing column using long simulations of longcrested, irregular waves with a variety of seastate parameters. By analyzing the physics of the process and using the measured crest elevation and the seastate parameters, the impact load distribution model is made seastate independent.
The impact model separates the wave impact problem in three parts:
– Given an incident crest in a specified seastate, calculate the probability of the crest giving a wave impact load above a threshold.
– Given a wave impact event above a threshold, calculate the distribution of the resulting peak load.
– Given a peak load, calculate the distribution of slamming pressures at one spatial location.
The development of the statistical model is described and it is shown that the model is appropriate for fixed and floating structures and for wave impact with both columns and the deck box.