bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pipeline Lateral Buckling Mitigation With Combined Sleepers and Mattresses
Authors: Hayes Kevin , Qi Xinhai , Duan Gang , Ren Lan , Jin Joe , Sharma Akhilesh 
Published: August 2024

Abstract
Buckle initiation devices, such as sleepers and distributed buoyancy modules, are typically adopted to initiate lateral buckles at pre-determined locations to release thermal expansion in a controlled manner to ensure pipeline integrity. For pipelines installed by S-lay, sleepers are desired as it is difficult for buoyancy modules to pass over the stinger rollers. If the thermal cyclic fatigue is critical in the pipeline design, pipeline lateral buckling designs may result in small sleeper spacing. As such, buckle reliability of conventional sleepers may be inadequate in some cases.
In this paper, lateral buckling mitigation with sleepers is investigated using finite element (FE) models for a water injection pipeline. Sensitivity analyses are performed on key input parameters including single and dual sleepers, lower bound and upper bound friction factors between sleeper and pipeline, berm effects on soil lateral resistances, and sleeper heights.
Based on the sensitivity study results, a mitigation solution combining sleepers and mattresses under the pipeline touch down zones is proposed and evaluated. It is found that sleepers combined with reduced touch down point lateral friction can reduce the maximum longitudinal strain and thermal fatigue damage by more than 50% as compared to using sleepers alone as mitigation. Therefore, this design adds a new option to allow increases in the sleeper spacing and improved reliability of buckle initiation.
Gripping Methodology: A New Approach Towards Enhanced Reliability for the Installation of Flexible Pipes
Authors: Godefroy Elise , Delannoy Laurent , Machnik Adam , Deheeger Antoine , Micas Guillaume , Belamri Nabil 
Published: August 2024

Abstract
During offshore installation / retrieval with tensioners, the flexible pipe is submitted to an axial tension due to the suspended catenary weight. To sustain this downward axial force and avoid any slippage during installation, a suitable squeezing load must be radially applied to the flexible pipe by tensioner tracks to ensure a proper transmission of the tightening force, by friction, at every layer interface, to the core of the pipe without crushing the pipe inner structure.
This paper presents a novel design methodology for the determination of the specific squeezing load during flexible pipe installation with tensioners. Various challenges are faced when determining the proper squeezing load to safely install flexible pipe, due to the diversity of interfaces above the tensile armour layers. Indeed, flexible pipe cross-sections may contain different sheath and tape materials (for mechanical, chemical, thermal, or manufacturing purposes). Every interface may behave differently depending on the environment (when exposed to water, temperature, etc.), and the level of contact pressure.
Therefore, the design challenge was to build a comprehensive approach relying on the following main aspects:
- Friction interaction between flexible pipe layers addressing influent parameters, thanks to an extensive small-scale test campaign,
- Statistical treatment of these data and validation through testing with complete flexible pipes,
- Development of Finite Element Analysis (FEA) Abaqus models to validate the load transmission mechanisms from the tensioner to the core of the flexible pipe,
- Validation through a large full-scale test campaign including tensioner onboard an installation vessel,
- Certification of the full methodology with an Independent Verification Agent (IVA).
This novel methodology is a key enabler towards even safer offshore operations as it constructs clear installation domains which prevent slippage events considering multiple factors. The methodology was built in compliancy with DNV-ST-N001 that details how to derive the friction coefficients and select appropriate safety factors for flexible pipe industry.
Automatic Drone Landing on a Boat: Theory and Preliminary Experimental Results
Authors: Falang Martin , Hinostroza M. A. , Bull Hove Peter , Sundvoll Thomas , Lekkas Anastasios M. 
Published: August 2024

Abstract
Recent rapid advances within autonomy for unmanned aerial vehicles (UAVs) make it possible to consider deploying them for critical operations in challenging environments, such as the ocean. Going even further, the combined operation of UAVs and autonomous surface vessels (ASVs) could be a strong enabler for exploration and search and rescue missions at sea, to name a few examples. The main contribution of this paper involves designing the perception, planning and control modules for the fundamental phase of such a collaborative operation, that is, the automatic drone landing of an UAV on an ASV. The perception system utilizes an Extended Kalman Filter that fuses the estimates from two computer vision systems, one based on deep learning and one on traditional edge detection approaches. The control system is a cascaded structure of position, velocity, and attitude control. The high-level planning is based on the GraphPlan algorithm and generates action sequences to solve three missions of different complexity based on a set of defined domain variables. The efficiency of the proposed solution is demonstrated via field trials involving a Parrot Anafi quadcopter landing on a helipad installed on DNV’s Revolt ASV. Our preliminary experimental results demonstrate that the system is capable of landing the UAV on the Revolt at sea, in conditions that were almost stationary, or involved forced rolling motion.
Friendly FPSO Hull Structure for Robot Inspection
Authors: Torres Zuniga Waldy J. , Videiro Paulo Maurício , Mendes De Sousa José Renato , De Almeida Costa Newton Bruno , Sudati Sagrilo Luis Volnei , Dos Santos Rizzo Nicolau Antonio , De Souza Silva Rodrigo 
Published: August 2024

Abstract
The Floating Production Storage and Offload system (FPSO) is widely used in offshore oil and gas exploitation. Traditional FPSO hull structures are typically constructed employing stiffened steel panels consisting of steel plates and closely spaced stiffeners. Classification societies require periodic full inspections of the cargo tanks. Nevertheless, the structural impediments created by these stiffeners can pose challenges or even prevent using autonomous equipment for remote inspection of tank structures. Additionally, inspection surveys with people inside the tanks are time-consuming and risky. Hence, a steel-concrete-steel sandwich plate system to address this challenge is proposed as an alternative solution to the conventional stiffened plate composition. Using sandwich panels in the bottom of oil cargo tanks and their longitudinal and transverse bulkheads smooths the surfaces by eliminating the need to use stiffeners, thus facilitating remote inspections with autonomous equipment inside the tanks. Furthermore, this approach can potentially reduce the time needed for periodic inspections of tank structures, following the recommendations set by classification societies to mitigate operational risks. The article presents the results of numerical ultimate strength analyses of sandwich panels and the initial scantlings of an FPSO hull main structure built with the proposed technology. Also, a comparative analysis of the relative total weight is performed.
A Numerical Simulation Method for Prediction of Ice Resistance and Ship Motion in Level Ice
Authors: Song Ming , Tong Zhe , Yuan Wei , Tian Bokang 
Published: August 2024

Abstract
Estimating ice resistance and ship motion in ice-covered region is important for the planning of operations and transport routes. This paper proposes a numerical simulation method for predictions of ice loads and ship motions in level ice. The dynamic interaction between ship and level ice is considered on basis of nonlinear finite element method. Numerical simulations between level ice and a ship are carried out by LS-DYNA software. The ice material model which can simulate ice crushing and bending failure modes is used. To consider the net thrust during ship-ice interaction, the user-defined load subroutine LOADSETUD that provides a means to apply nodal loads as a function of velocity is used. In addition, the water effect on the level ice model is taken into account by using a nonlinear discrete spring model. The model tests of an icebreaker navigating in level ice is used to test the presented method. The predicted results including ice resistance, net thrust and attainable speeds for given ice conditions are compared with the model test data. The comparison shows a generally good agreement, which indicates that the presented method is able to give reasonable predictions. Furthermore, the comparison between the numerical results obtained by the rigid ship and the deformable ship is made. The ship structural response during ship-level ice interaction is investigated.
Active Control of Distributed Subs With Anti-Slip Logic for Torsional Vibration Damping in Drilling
Authors: Nüsse Pauline Marie , Ambrus Adrian , Aamo Ole Morten 
Published: August 2024

Abstract
Previous publications showed that torsional vibrations of the drill pipe can be attenuated by subs equipped with sleeves in which the pipe rotates and is subjected to passive or actively controlled magnetic damping. The damping force depends on the relative velocity between the pipe and the sleeve and an adjustable damping coefficient, but is limited by the friction between the sleeve and borehole wall. If the commanded damping coefficient is too large, the sleeve will slip, potentially harming the borehole wall or casing, and itself. In this paper, we combine a previously designed on-off controller with anti-slip logic which learns the maximum available damping force and prevents the on-off controller from commanding a damping coefficient that leads to slippage. Occasional slippage is allowed, however, in order to learn the maximum damping force under changing down-hole conditions. Simulations demonstrate that both reduction in slippage and improved vibration damping are achieved by the modified controller.
Study on Structural Design Scheme of Motion Suppression System
Authors: Yin Yan , Yuan Hongtao , Zhou Bo , Du Yuchun , Wang Yuhan , Wang Chao 
Published: August 2024

Abstract
In order to solve the problem of poor motion performance of cylindrical FPSO, a new motion suppression system scheme is proposed which can make the platform meet the requirements of dry tree operation. The structure design scheme has an impact on the structure safety, construction technology, construction cost and other factors, so it is very important to make clear the structure design scheme of the motion suppression system.
Based on the limitations of the construction site, construction economy, weight control requirements and other factors, this paper proposes a structural design scheme. In the design process, the whole life service cycle of the platform is fully considered, and key parameters are optimized to save structural weight and construction cost. At the same time, the local strength analysis of the connected structure is carried out by finite element method and obtain the final structural design scheme. The scheme provides a reasonable structural optimization and a reference for the structural design of large structures.
Conceptual Design of Innovative Relocatable Wellhead Platform Using Multi-Column Structure “MCT” With Both Bottom Founded and Floating In-Place Capabilities
Authors: Bakti Farid Putra , Tahar Arcandra 
Published: August 2024

Abstract
This study addresses the design challenge of a relocatable wellhead platform that satisfies the complex operational and environmental requirements of both shallow and deeper water hydrocarbon extraction. A platform design capable of catering to three distinct fields: the shallow water A Field (∼20 m water depth) and the deeper waters B Field (∼40 m water depth) and C Field (∼65 m water depth), each with a production life expectancy of less than 10 years is shown in this study. Other requirements such as the use of dry-tree, simpler fabrication and decommissioning method, and cost effectiveness were also imposed on the proposed solution.
To answer these requirements, a Multi-Column Structure (referred to as “McT”) is proposed as the solution. In the initial stage, McT serve as a gravity-based substructure for the shallower water A Field. The McT’s fabrication and integration with the topside will take place in a dry dock. Subsequently, the integrated McT will be floated to the installation site, where it will be ballasted and placed on the seabed. This wet-tow option provided more flexible, economical, and simpler installation and fabrication method when compared to the jacket type structure. Furthermore, the size of the columns is designed with a dimension where a simple steel rolling devices may be utilized to fabricate the hull. Ring skirts and driven pile are incorporated into the McT’s foundation design to provide the in-place stability and to fulfill seismic requirement during its fixed mode utilization. Notably, well conductors and trees (up to 7 wells) will be situated alongside the McT, facilitating well drilling and production.
This study’s primary objective is to devise a single McT substructure capable of accommodating the operational needs of the A, B, and C Fields. The scope of the study includes the summary of Substructure (Hull) Configuration Design, Foundation Design, Wire Tendon and Suction Pile Design, Global Performance Analysis, Pre-Service stability Analyses, Flexible and Top-Tensioned Riser Design and qualitative cost comparison with jacket type offshore platform. This innovative platform design offers a versatile, relocatable wellhead platform solution, tailored to the specific needs of multiple fields, while satisfying stringent criteria for technology, operational feasibility, and cost-effectiveness.
On the Validity of Miner’s Rule for Pile Foundations in Sand
Authors: Hagemann Anne , Grabe Jürgen 
Published: August 2024

Abstract
The current design practice for offshore monopiles applies widely accepted simplifications of complex irregular loading scenarios. Highly cyclic loads from varying directions offshore are simplified by means of classification methods. This procedure involves reordering individual cycles in irregular loading scenarios by frequency, mean load, and amplitude. This approach is based on the assumption that the resulting accumulated deformation in the soil is independent of the ordering of the cycle packages, i.e. the validity of Miner’s rule. Different contributions in literature investigate the validity of Miner’s rule by evaluating the effect of the ordering of cycle packages on the resulting damage in the soil, i.e. the accumulated volumetric strain. This paper addresses the question of the validity of Miner’s rule from a different perspective. It investigates the load-displacement behaviour of sand in direct simple shear tests due to dynamic load scenarios. Hence, the load sequences during testing vary while the energy spectrum being employed to generate the irregular load signals remains constant. This method enables capturing natural conditions offshore during testing and allows for comparing individual loading scenarios as the wave spectrum in the frequency domain defines the distribution of wave amplitudes. The test program is carried out on medium dense fine silica sand. The test results are evaluated regarding the accumulated volumetric strain and relate to previous studies on the validity of Miner’s rule in sand.
Investigating Statistical Modelling of Excitation Forces in Inhomogeneous Waves
Authors: Laflèche Sébastien , Ommani Babak , Kristiansen Trygve , Fouques Sébastien 
Published: August 2024

Abstract
In coastal areas, and especially fjords, the wave field can present inhomogeneities that affect the responses of floating bridges among other very large floating structures. Recent studies have begun to include the effects of such inhomogeneities in the design phase. To that end, it is necessary to estimate not only the spectrum of the loads on the different pontoons, but also their coherence with each other. However, such information is usually not directly available everywhere, especially for coherence, as hindcast data does not contain phase information, and buoy data is sparse. Thus, assumptions need to be made for the coherence function.
This study presents a benchmark of the various assumptions made in recent studies of fjord-crossing floating bridges, on the coherence of linear excitation forces on pontoons. Synthetic inhomogeneous wave fields were generated from an analytical solution, allowing to compare the forces obtained from the various assumptions to true values, not accessible otherwise at sea. This was done by placing “islands”, modelled by large circular cylinders, in an infinite ocean with incident homogeneous short-crested waves. It was found that most assumptions perform well for two pontoons either very close or far from each other. A new assumption is also proposed, adapted to measurements from heave-pitch-roll buoys. It performed systematically better than the historical assumptions for wavelengths larger than the pontoons, and for any distance between them.
Effects of Second-Order Hydrodynamic Loads on a Barge-Type Floating Wind Turbine Platform With Moonpools
Authors: Tan Lei , Liu Yingyi , Ikoma Tomoki 
Published: August 2024

Abstract
Barge-type floating wind turbines with moonpools have been shown to have reasonably good seakeeping performance in the literature. Following our previous studies, the main purpose of this work is to develop a time-domain numerical analysis tool implemented with the open-source hydrodynamic code NEMOH for conducting pre-hydrodynamic analysis in frequency domain. Special attention of this study is paid to quadratic transfer function (QTF), which is calculated by NEMOH and is included in time-domain simulations. To investigate the effect of second-order wave drift force on motion responses, we considered a barge-type floating foundation prototype under the available typhoon-induced wave condition and calculated the responses in frequency and time domains. It was found that the moonpool resonances may lead to considerable difference-frequency QTFs. The numerical results including difference-frequency QTF influence showed that the barge with moonpools had large-amplitude horizontal resonant motions at low frequencies, which dominated the total responses. This result indicates that the second-order wave drift loads play an important role in surge and sway responses. Regarding heave and roll (and pitch) motions, the wave drift loading can also cause the responses at low frequencies, but these low-frequency response amplitudes are generally small and non-dominant.
Global Dynamics of a Hang-Off Power Cable Immersed in the Flow Near a Fixed Offshore Wind Turbine
Authors: Liu Guojun , Yao Yong , Long Yi , Zhang Cheng 
Published: August 2024

Abstract
The hang-off power cable extending from the offshore wind turbine tower takes the significant responsibility of electric energy transportation. The scour, tide and wave have associated action in promoting the exposure and spanning of the hang-off power cable in the flow near fixed offshore wind turbine. The analysis of the global dynamics of the hang-off power cable is the basis for evaluating its safety. In the present study, a nonlinear dynamic model for the hang-off power cable is established based on the absolute nodal coordinate formulation (ANCF) and marine hydrodynamics. The absolute position and slope coordinates in the model can avoid the coordinate transformation, while the employed geometric relationships accurately describe the complex deformation of the cable. The hydrodynamic and seabed loads on the cable are evaluated by Morrison equation and linear pipe-soil interaction model, respectively. The flow velocity near the fixed offshore wind turbine is obtained through the numerical simulation of computational fluid dynamics (CFD), regarding as an external input of environmental condition for the hang-off power cable. By considering different incidence angles of inlet flow, the distributions of the dynamics along the cable are fully examined. This paper verifies that this model can reliably evaluate the motion characteristics of hang-off power cables, and simulates and calculates the overall dynamic response of the hang-off power cable under actual sea conditions. The study is expected to further support the wear and fatigue assessment of the hang-off power cable.
Statistical Validation of Surfaced Submarine Seakeeping Simulations Based on Open Water Tests
Authors: Büsken Wiebke , Krüger Stefan 
Published: August 2024

Abstract
Submarines are frequently required to operate in surfaced condition, partially in harsh seaways. Since diving is not always possible or permitted, an accurate prediction of a submarine’s seakeeping performance at the surface becomes essential for safe operation. The seakeeping of a surfaced submarine is a complicated problem of motions in all six degrees of freedom, which strongly depends on the respective parameter combination of seaway, forward speed, encounter angle, and surface stability. In this paper, time-domain seakeeping simulations are performed for a modern submarine hull form in short-crested irregular waves using the potential flow theory-based computation method E4-ROLLS. The simulation results of the roll, pitch and heave motions are compared with data obtained from open water model tests. These model tests were recently performed on a bay in Germany using free-running submarine models and specifically focused on the surface stability’s influence on the sea-keeping in natural seaways. The presented research contributed to the development of a novel surface stability regulation DMS 1030-2 for submarines of the German Navy.
A Novel Approach for Ship Digital Twin Optimisation: Principal Component Analysis-Driven Distortion Base Mode Selection and Utilisation
Authors: Song Seung Woo , Jin Chungkuk , Kim Do Kyun 
Published: August 2024

Abstract
This study aims to improve the efficiency of distortion base mode selection using Principal Component Analysis (PCA) and enhance structural response estimation techniques for digital twin applications in the maritime structures. Real-time determination of loads on a structure is essential for digitalisation in the maritime sector. Methods such as modal superposition and inverse finite element methods have been investigated to calculate loads at arbitrary points from a limited number of sensors. The objective of this study is to estimate loads by using a conversion matrix constructed by distortion base modes. In this study, modes are selected based on the response to regular waves. To achieve this, a distinct algorithm has been developed to select orthogonal modes. This study proposes a novel mode selection method by implementing PCA, which enables obtaining the most representative direction. Wave load case with responses which is most parallel to this direction is determined to be the first mode. To validate our methodology, we estimate hotspot stresses on an FPSO. This method reduces computation time while maintaining high accuracy of estimation. These findings show potential for application to other offshore structures. Further research using actual measurement data is expected to enhance the validity and reliability of these techniques, making a significant contribution to the field of maritime structural analysis and digital twin technology.