bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of Riser and Well System Response Predictions to Full-Scale Measurements in a Shallow Water Harsh Environment
Authors: Walker Karen M. , Agarwal Puneet , McNeill Scot , Bhalla Kenneth , Baker David A. , Zheng Haining 
Published: October 2017

Well system fatigue accumulated during drilling operations from mobile offshore drilling units (MODUs) has been a topic of intensive study in recent literature. A variety of efforts from individual operator studies to industry-wide joint industry projects have been launched in an effort to improve understanding of both the load and resistance elements of well system fatigue assessment. A key uncertainty in current predictive modeling practice is the level of conservatism inherent in that modeling, as compared to real-life system response. Collection of good quality, full-scale field measurement data is a key component in evaluating this uncertainty.
A full-scale measurement campaign was recently conducted on a 6th generation MODU during drilling operations in a shallow water region with a harsh environment. The measurement system on board the vessel captured vessel, riser and lower marine riser package (LMRP) accelerations and angular rates, along with riser tensioner pressures. Concurrent environmental measurements were acquired via wave rider buoy and acoustic Doppler current profiler (ADCP) located near the mobile offshore drilling unit (MODU), capturing wave height, period and direction, and full-depth current profiles. This paper focuses on data collected for one well during the winter months where significant wave heights at the drilling site varied from 6ft to 26ft.
In this paper, a comparison between measured and predicted riser and well system loading is presented. The predicted riser and well system response is based upon global riser analyses performed in both the frequency and time domains to evaluate the effect of linearization in the modeling process.
Loading demand on the well system is also presented as cycle-range histograms. This paper also summarizes the conclusions from the comparisons of these measurements with other published measurement campaign data. While loading derived from previous riser analysis studies have been found to be “conservative” as compared to full-scale measurements, this study finds that the predicted and measured responses match quite well. Furthermore, it is also shown that the frequency domain results are adequate for this study, suggesting that the nonlinearity within the riser and well system for the conditions studied is relatively minor.
Application of Wake Shielding Effects With a Finite Element Net Model in Determining Hydrodynamic Loading on Aquaculture Net Pens
Authors: Turner Adam A. , Steinke Dean M. , Nicoll Ryan S. 
Published: October 2017

A net wake shielding and self shielding model has been developed to accurately estimate the hydrodynamic loading on fin-fish aquaculture installations in the dynamics simulation software package ProteusDS. The software was developed to determine the loads and motions of various ocean engineering systems in response to wave, wind and current conditions. The effect of containment net hydrodynamic wake shielding is important to avoid overly conservative estimation of loads on fish farm installations. The reduction in fluid velocity through a net can be significant in many cases, leading to decreased loading and changes in motion on downstream nets and mooring components.
The developed wake shielding model uses a wake volume approach to estimate a reduction in flow velocity and hydrodynamic loading on downstream components within the wake volume. Self shielding effects of adjacent twines within a net are also considered, as interactions between netting twines can reduce hydro-dynamic loading on nets at certain angles of incidence to the oncoming flow. This paper presents the developments both of the wake shielding and self shielding models and demonstrates the capability to accurately predict current forces acting on successive net pens by comparing simulation results with published results from tank tests, as well as a comparison of measured tensions on mooring lines at a full scale fish farm. A method for determining netting drag coefficients based on Reynolds number variations is also presented and compared to experimental drag tests on planar nets to confirm its validity.
Calculation of the Hydrostatic and Structural Integrity of Docking Sequences
Authors: Dankowski Hendrik , Weltzien Charlott 
Published: October 2017

The conditions of competition within ship yards are changing. The current market situation requires a new orientation of the Pella Sietas ship yard with flexible solutions for new ship types. Complex, heavy and ice-going ships show one way for future designs. In view of all the technical difficulties involved in such challenging projects, the first question must be how to handle these heavy constructions with the yards building facilities available. The Pella Sietas yard is using a floating platform for newbuildings. The question arises whether or not this platform is still capable and suited for this kind of ship types.
The docking procedure is a complex multi-body interaction that copes with hydrostatic and structural challenges. The docking operation is regulated by the sequence of flooding and emptying ballast water tanks of the dock. At any time of this dynamic operation the hydrostatic stable equilibrium of ship and dock must be ensured.
When the ship becomes afloat the keel block system transfers the ships weight on the structure of the dock. It must be ensured that the resulting tensions and deformations do not exceed the maximum permissible values.
This paper describes a fast calculation method that determines the mentioned hydrostatic as well as the structural investigations during the docking procedures.
The method implies a numerical progressive flooding simulation that calculates the hydrostatics of ship and dock under consideration of their interaction by dock blocks together with the ballasting sequence in the time domain. Furthermore it calculates the block forces distribution by applying the deformation method. In the calculation process ship and dock are modeled as Timoshenko beams and the dock blocks as non-linear spring elements. Moreover the shear force and bending moment distributions of ship and dock are calculated and the deflection lines are presented.
Therefore, the described method enables the ship yard to evaluate quickly the possibility of building new types of ships on the existing building platform and allows evaluating which modifications are useful to enlarge the capacity of the platform even further.
It provides a useful tool to minimize local and global stresses and deformations of the interacting bodies during the whole docking procedure by fast optimization of the block system arrangement and the ballasting sequences.
As a result the described method could expand the range of flexibility of a given floating dock structure. In addition, the whole hydrostatic and structural integrity of docking sequences can be computed faster and more accurate even at a very early project stage.
An Improved Approach for Modelling Reliability of Buckle Formation for Subsea Pipelines
Authors: Haghighi Ali , Rai Jitender , Le Maout Yann , Oliphant John 
Published: October 2017

Lateral buckling (LB) design for subsea pipelines generally requires reliability analysis to evaluate the probability that a lateral buckling mitigation system will behave as expected, which means that the engineered initiators will trigger buckles sequentially before any uncontrolled buckle can form in between. As various parameters involved in the buckle formation process are uncertain (soil characteristics, residual horizontal and vertical Out of Straightness (OOS) after pipelay), a probabilistic approach is used to assess the likelihood that the pipeline will buckle at the intended locations. The Safebuck JIP has developed a structural reliability model of the pipeline expansion process to calculate the probable virtual anchor spacing (VAS). This model can be used to assess the reliability of buckle initiation on the design of pipelines susceptible to lateral buckling.
The buckling response of a pipeline will always be inherently uncertain because project specific OOS information is not known prior to pipelay. The Safebuck guideline focus is on horizontal OOS whereas the impact of bathymetry is addressed in a high level fashion, with no clear methodology. This paper presents an alternative approach to account for the effects of bathymetry on the reliability of buckle formation. The model is a significant advance on the current method for estimating buckle formation reliability and brings other important benefits such as capability for modelling any transient profiles of pressure and temperature.
In this paper the difference between the horizontal residual OOS in pipelines for different pipelay methods is discussed, and it is shown that the method of pipelay can have a significant effect on pipeline horizontal residual OOS. The impact of change in horizontal OOS on reliability of buckle formation has been assessed.
Qualification and Certification of Polyester Rope for Seabed Contact
Authors: Gabrielsen Øystein , Larsen Kjell 
Published: October 2017

The Aasta Hansteen spar in the Norwegian Sea is designed to be moored with a taut polyester rope mooring system.
The water depth at the field is 1300 meters, and due to the short installation season the most efficient hookup is with pre-installed mooring lines, which require the mooring lines to be laid down on the seabed.
DNV certification does not allow seabed contact for polyester ropes unless proven that no soil ingress and damage takes place. To be able to certify the ropes Statoil developed a test method including contact with soil, rope movement and forced water flow through the filter construction. Full scale tests were performed with actual rope and Aasta Hansteen soil, both in laboratory and at site.
This paper discusses the certification requirements and presents adequate qualification test together with results from testing.
Emission Reduction in Shipping Using Hydrogen and Fuel Cells
Authors: Jafarzadeh Sepideh , Schjølberg Ingrid 
Published: October 2017

Despite various technical and operational improvements, shipping remains a contributor to global emissions of greenhouse gases, nitrogen oxides, and sulphur oxides, among others. As a part of its efforts to limit adverse health and environmental impacts of shipping, the International Maritime Organization (IMO) has enforced regulations to control these emissions. In addition, some countries, such as Norway have imposed additional regulations to control emissions further. Environmental regulations and concerns call for an improved environmental profile within shipping, which motivates this study.
Alternative fuels and power systems are required for a substantial reduction in emissions from shipping. Hydrogen and fuel cells are among the most promising solutions from an environmental perspective. A fuel cell is an electrochemical conversion device, which produces electricity through the reaction of an oxidant with hydrogen or another hydrogen-rich fuel, such as a hydrocarbon fuel. Since the electricity production does not entail fuel combustion, emissions are reduced substantially. When hydrogen gas is used as the fuel, only water is formed as the byproduct. In addition to emitting ultralow or zero emissions, fuel cells offer high energy conversion efficiency, low noise level, and low vibration.
The Norwegian energy system is based on electricity from renewable energy sources and mainly hydropower. Renewable energy output is strongly affected by the weather conditions, among other factors, and the supplies fluctuate accordingly. There is a need for a means to store and use the renewable energy surplus. In addition, from a technical point of view Norway still has potential to further develop hydro and wind power. Excess power can be used for production of hydrogen through water electrolysis, which in turn can fuel different means of transportation, such as shipping.
This paper aims at contributing to the research body on the use of hydrogen and fuel cells in shipping. First, a short introduction to hydrogen fuel and fuel cells is given. Then, an elaboration on pros and cons of powering vessels with fuel cells is presented. After providing an overview of current marine applications of fuel cells, the paper discusses potential vessels, which can benefit from this technology. Finally, the environmental benefits of using fuel cells are shown through a preliminary case study. Data from the Automatic Identification System (AIS) in the Norwegian waters is used for estimating operational profile of a vessel, its current emissions, and potential emission reduction by using hydrogen and fuel cells. The results of this study show the potential of hydrogen and fuel cells in reducing emissions of shipping and set forth the research gaps.
Fracture Testing of Existing Structures Without the Need for Repairs
Authors: Walters C. L. , Bruchhausen M. , Lapetite J.-M. , Duvalois W. 
Published: October 2017

It is sometimes necessary to find the toughness of existing structures without damaging them. Examples of this scenario include situations in which the material is suspected of being brittle or service life extensions. However, fracture testing is inherently destructive. Removing material for Charpy or Crack Tip Opening Displacement (CTOD) specimens can result in expensive repairs. The Small Punch Test (SPT), which has been developed for monitoring programs in the nuclear industry, offers a test method that requires such small amounts of material that the test can be performed in a practically non-destructive way.
A pilot project was conducted to determine if the SPT can be applied to steels of use in maritime and offshore applications. The results of the pilot project showed that the SPT can identify behavior related to the ductile to brittle transition for an example S355 steel. Therefore, the SPT can provide valuable information for predicting fracture properties relevant to structural-level behavior of steel, such as Charpy transition and estimates of CTOD values in the lower shelf and lower portion of the ductile to brittle transition curve.
In the end of this paper, a theoretical framework for transferring results from SPT to CTOD or Charpy testing is outlined.
Fatigue Capacity of Wellhead Housings
Authors: Kuzmichev Sergey , Rodriguez Garcia Javier , Aronsen Kristoffer H. , Grytøyr Guttorm , Kirkemo Finn , Simonsen Erik 
Published: October 2017

The issue of wellhead fatigue has been given significant attention during recent years. The complexity of the wellhead system in terms of interactions betwe[en conductor (low pressure) and wellhead (high pressure) housings leads to various analysis methods being proposed to evaluate fatigue damage in the system. Most of the critical base material hotspots are located in the wellhead housing region where the loads start to distribute between the high- and low pressure housing and the load paths are highly complex varying for different input parameters. Due to this, detailed fatigue analyses are typically performed on a project to project basis for the same wellhead geometry. This paper proposes an approach that simplifies the analysis of the base material hotspots in the housings and makes it independent of where the specific type of the wellhead system is used. It is suggested to consider the housings of the wellhead system as one component with a single characteristic M-N curve, or a few M-N curves if complexity requires so. The M-N curve is a specialization of the standard S-N curves provided in rules and standards. They are generated by combining the calculated load-to-stress curve at a given hotspot with the applicable S-N curve. The load used as a reference is typically a cross-sectional moment at the top of high pressure housing.
For these purposes 3D FE models have been developed for two principal wellhead types, rigid lock and non-rigid lock. The models are used to investigate the effect of different boundary conditions and applied loading on M-N curves for each hotspot analysed. Sensitivity studies have been performed for several parameters that are considered important in wellhead fatigue analysis. Based on the sensitivity studies, the effect of each parameter on typical base material hotspots is presented.
This paper provides estimates for the spread in the M-N curves for each individual base material hotspot in the wellhead housings. Results indicate that a single characteristic M-N curve per wellhead system type can be selected to represent the wellhead housings. In addition, based on results from the analyses carried out, recommendations regarding generalized boundary conditions to obtain a characteristic M-N curve for a specific wellhead type have been given.
Efficient Evaluation of Long-Term Response for Design of Components of Offshore Structures
Authors: Videiro Paulo Mauricio , Sagrilo Luis Volnei Sudati 
Published: October 2017

This paper compares two approaches for the estimation of long-term response of wave load effects on offshore structures. These approaches are applied to estimate the extreme value of the cross section interaction ratio of a tubular component of the bracing system of a semisubmersible platform. The tubular component is subjected to axial loads and bending moments due to static loads and wave effects. The iteration ratio in the ultimate limit state is defined by applying design criteria derived from API RP-2A LRFD [6]. The approaches are also applied to estimate the long-term response of a single degree of freedom system due to wave actions.
The first approach is based on the proposals of Videiro and Moan [3]. The results of the first approach are compared with a new model of long-term response estimation, based on the up-crossing rate distribution of the response process.
Design of Conventional and Assembled Bulkhead for a Flowline Bundle
Authors: Achani Dasharatha 
Published: October 2017

A bundle, in general, comprises flowlines enclosed with carrier pipe and bulkheads at each end. Under operational load conditions, bundle expands in each end and releases forces from inner pipe and induces forces in outer pipe. The bulkheads that try to restrict the bundle expansion are subjected to interface forces on both sides and shall be designed and manufactured against the codes in compliance with DNV-OS-F101. A conventional bulkhead, referred as forged Bulkhead, is typically manufactured by a hot forging process as per the specified standard. For the forged bulkhead, the main body, surface and nibs shall be of specified material grade and the material shall be quenched and tempered after forging. Previous experience from different projects shows that it is sometimes hard for the forged bulkhead to achieve the results from mechanical testing to meet standard requirements and it is even expensive.
A bulkhead manufactured by assembled method can be considered as an alternative. The assembled bulkhead, in the present work, comprises of a plate with boreholes. The small pipe inserts of the respective borehole sizes are fitted through boreholes and circumferentially welded to the bulkhead plate. The ends of each pipe inserts are further welded with the ends of respective size of flowlines of the bundle in one side and the spools on the other side.
The work in this paper presents general design and methodology for the forged bulkhead of 4-line bundle. Further, the work also presents an alternative design for a conventional forged bulkhead. The design is based on FE analyses performed using finite element (FE) tool ANSYS and 3D FE models established by using advanced solid elements from ANSYS. For the same load conditions, the results from analyses show that the assemble bulkhead meets the acceptance criteria from the design methodology and can be considered as an alternative provided that appropriate welding techniques and NDE procedure are ensured in the weld root area of the welds between the pipe inserts and bulkhead plate.
Identification of Key Elements for Compliance of the IMO Polar Code Requirement of Minimum 5 Days Survival Time
Authors: Solberg Knut Espen , Barane Endre , Gudmestad Ove Tobias 
Published: October 2017

IMO has developed the functionally based Polar Code, which entered into force 01.01.2017. The code requires marine operators to provide lifesaving equipment that ensures a minimum of 5 days survival time. This requirement puts additional strain on the existing life-saving appliances.
To identify the key elements for compliance of the IMO Polar Code, a full-scale exercise (SARex, (April 2016)) was initiated and organized by University of Stavanger, the Norwegian Coast Guard and GMC Maritime. The object of the SARex full scale exercise was to identify the gaps between the functionality provided by existing SOLAS approved safety equipment and the functionality required by the Polar Code. The exercise was conducted with the help of the vessel KV Svalbard (Norwegian Coast Guard), and participated by leading experts from industry, governmental organizations and academia.
The following topics were specifically addressed in the exercise that took place in the marginal ice zone of the coast of Svalbard late April 2016:
1. Functionality of survival craft and PPE (Personal Protective Equipment) polar conditions.
2. Coast Guard’s search and rescue procedures, including handling of mass evacuations in Polar Regions.
3. Functionality of Personal/Group survival gear according to the requirements defined in the IMO Polar Code.
Survival for 5 days according to the requirements defined in the IMO Polar Code in a life raft represents a large challenge with regard to design of rescue craft, design of PPE (Personal Protective Equipment), rations and on-board organization. As the IMO Polar Code is functional based, a holistic approach has to be utilized when assessing the survival chain. For an assessment of the survival chain to be conducted in a sustainable manner, key elements essential for survival in a life raft have to be identified and prioritized.
Designing a survival chain applicable to maritime industry also involves considering commercial, economic and operational restrictions.
The paper will elaborate on the key elements essential for a minimum of 5 days survival in a life raft based on the findings identified in the Phase 1, Functionality of survival craft and PPE (Personal Protective Equipment) polar conditions, of the SARex exercise. The findings will be assessed and evaluated based on industry limitations.