bluuebunny/crossref_metadata_2025_split huggingface dataset:
Integrated Probabilistic-Mechanistic Deterioration Modeling for Preventive Maintenance of Aging Fixed Offshore Jacket-Type Platforms
Authors: Srikanth Ishwarya , Arockiasamy M. 
Published: December 2020

Abstract
Most of the offshore platforms in the world are designed as steel jacket-type platforms for oil and gas exploration and production. A significant amount of research has been carried out over the past two decades to understand ageing and the associated degradation of offshore structural members. The paper proposes an approach for prioritization and preventive maintenance of jacket-type platform. Offshore platform maintenance systems are dependent on deterioration models to predict the future condition of structural elements. The input for these models consists of condition states of different jacket elements and their evolution as a function of time. One of the challenges includes lack of availability of condition state records for the aging platforms. This paper proposes a methodology for developing deterioration models when there is a scarcity of inspection records.
This study focusses on developing a methodology for i) the impact ranking of different bracing member groups of the jacket platform and ii) deterioration models using integrated probabilistic-mechanistic modeling. Firstly, a typical jacket-type offshore platform under the North Sea conditions is modeled and analyzed under wave and current loads. Then, nonlinear static (pushover) analyses are performed for the undamaged jacket platform. The criticality of the different groups of bracing elements is obtained in terms of Residual Resistance Factor by carrying-out redundancy analyses. Soil-structure interaction effect is considered in the analyses and the results are compared with the hypothetical fixed-support end condition. The member groups are then ranked based on their impact on the ultimate strength of the jacket platform. Secondly, deterioration models for jacket legs and bracings in splash and immersion zones are obtained based on integrated mechanistic-probabilistic approach. An idealized uniform corrosion model is used in generating the member condition state probabilities. Condition state probabilities for jacket legs and bracings are then generated using Monte Carlo simulations. The residual service life of the jacket elements is predicted from the deterioration models which could be utilized for preventive maintenance of the jacket platform.
A Fracture Characterization Framework for Large-Scale Marine Metal Structures
Authors: Londono Juan G. , Mobasher Mostafa E. , Woelke Pawel 
Published: December 2020

Abstract
Prediction of large-scale marine structures under extreme loading conditions (e.g. impact, fire) requires the use of computational tools that are both accurate and efficient. To resolve models at this scale, engineers normally use shell elements in which two of the (in-plane) dimensions are much larger than the third (thickness) one. Herein, we propose a consistent characterization framework for shell-element models commonly used in metal marine structures. The underlying model is based on a three stress-invariant plasticity model that accounts for the effects of stress triaxiality and shear-dominated stress states and accounts for the micromechanical void growth and coalescence that leads to fracture. This framework serves as both a constitutive model as well as a back-end calibration engine which outputs material cards that can be readily used with commercial finite element solvers like LS-DYNA and Abaqus. The calibration framework supports data-driven constitutive models that require engineers to prescribe the Fracture Locus (FL) and Instability Curves (IC) from experimental data, such as the Johnson-Cook model. Moreover, the calibration framework uses the underlying physics based model to computationally generate additional surrogate data that compliments the experimental testing. Thus, it allows the analyst to calibrate a material model based on limited experimental data, hence, reducing the costs associated with data acquisition and processing. A standalone calibration tool (VistaCal) that highlights the benefits of this characterization framework is also presented.
Jump Bifurcation Phenomenon During Varying Wind Speeds in Floating Offshore Wind Turbines
Authors: Jose Alwin , Falzarano Jeffrey 
Published: December 2020

Abstract
Floating Offshore Wind Turbines (FOWTs) are susceptible to an instability which has come to be called “negative damping”. Conventional land based wind turbine controllers when used with FOWTs may cause large amplitude platform pitch oscillations. Most controllers have since been improved to reduce motions due to this phenomenon. In this paper, the motions induced using one of the original controllers is studied.
The current study is performed using the coupled time domain program FAST-SIMDYN that was developed in Marine Dynamics Laboratory (MDL) at Texas A&M University. It is capable of studying large amplitude motions of Floating Offshore Wind Turbines.
FOWTs use various controller algorithms of operation based on the available wind speed depending on various power output objectives i.e., to either maximize or level out power absorption. It is observed that the transition region for controllers is often chaotic. So most studies focus on operations away from the transition region i.e., both below and above the transition wind speeds. Here we study the transition region using the theoretical insight of non-linear motion response of structures. This study reveals the presence of a very interesting and potentially hazardous nonlinear phenomenon, bifurcation. This finding could help explain the chaotic motion response that is observed in the transition region of controllers. Understanding the nature and cause of bifurcation could prove very useful for future design of FOWT controllers.
Active Absorption of Random Waves in Wave Flume Using Artificial Neural Networks
Authors: Ramos Áureo I. W. , Fernandes Antonio C. , Thomaz Vanessa M. 
Published: December 2020

Abstract
A wave flume is primarily intended to reproduce actual sea conditions in order to provide a reliable means of testing for small scale models. The realization of scaled tests is extremely important for the validation of a project in real scale, since, through the laws of similitude, such tests make it possible to predict the behavior of structures in the ocean as well as their performance during operation. This research aims to develop, test and validate an active control algorithm for wave absorption in a 2D wave channel — that is, when the waves propagate in only one direction — based on artificial neural networks (ANN). The ANN control algorithm relies on the linear wave theory and the principle of time reversal of wave propagation, i.e. the phenomenon of wave absorption corresponds to the wave generation when observed in the reverse direction of time. Through this principle, data from wave generation experiments, after proper manipulation, are used to train an ANN capable of generating the control signal used to move the wave generator device, this time as a wave absorber.
Experimental Identification of an Advanced Spar’s Low Frequency Drag Damping in Waves
Authors: Wright Christopher , Yoshimoto Haruki , Wada Ryota , Takagi Ken 
Published: December 2020

Abstract
Climate change and increasing population growth are accelerating the need for new clean renewable energy generation. One such proposed type of renewable energy is offshore floating wind, which has yet to reach a convergence as to the optimum type of floating platform to support a wind turbine. To date there has been numerous proposals of novel floating platforms with unique hull characteristics. One such type is the advanced spar, which has a large area of sharp edges and therefore considerably different hydrodynamic viscous effects than typical cylindrical platforms.
Prediction of a floating body’s low frequency drag damping is crucial to successfully predicting the horizontal motions. Calculation of the viscous effects have been seen to have the most uncertainty. Published literature shows that the viscous drag effects of floating bodies either increase or decrease with increasing wave severity as compared to still water decay tests.
In this paper a combined experimental and numerical method for identifying low frequency viscous damping effects on the hull of a moored platform is introduced. An initial offset is applied to the platform, which is then released in still water and regular sinusoidal waves. The experimental results will then be compared to a weakly nonlinear time domain model in order to identify how the drag coefficients vary with wave conditions. Discussions on Keulegan–Carpenter (KC) number dependent damping are given. Finally simulations using results from these experiments are compared against a full scale deployed floating platform in multi-directional waves, current and wind.
Wear-Factor Prediction Based on Data-Driven Inversion Technique for Casing Wear Estimation
Authors: Mittal Manish K. , Samuel Robello , Gonzales Aldofo 
Published: December 2020

Abstract
Wear factor is an important parameter for estimating casing wear, yet the industry lacks a sufficient data-driven wear-factor prediction model based on previous data. Inversion technique is a data-driven method for evaluating model parameters for a setting wherein the input and output values for the physical model/equation are known. For this case, the physical equation to calculate wear volume has wear factor, side force, RPM, tool-joint diameter, and time for a particular operation (i.e., rotating on bottom, rotating off bottom, sliding, back reaming, etc.) as inputs. Except for wear factor, these values are either available or can be calculated using another physical model (wear-volume output is available from the drilling log). Wear factor is considered the model parameter and is estimated using the inversion technique method. The preceding analysis was performed using soft-string and stiff-string models for side-force calculations and by considering linear and nonlinear wear-factor models. An iterative approach was necessary for the nonlinear wear-factor model because of its complexity. Log data provide the remaining thickness of the casing, which was converted into wear volume using standard geometric calculations.
A paper [1] was presented in OMC 2019 discussing a method for bridging the gap. A study was conducted in this paper for a real well based on the new method, and successful results were discussed. The current paper extends that study to another real well casing wear prediction with this novel approach. Some methods discussed are already included in the mentioned paper.
A Sensitivity Study of Vessel Hydrodynamic Model Parameters
Authors: Han Xu , Sævik Svein , Leira Bernt Johan 
Published: December 2020

Abstract
In the recent decade, maritime and energy industries have realized the potential of using operational data in combination with a virtual replication of the real physical asset, termed the digital twin. The digital twin then serves as a platform for data management, asset monitoring, and inspection and maintenance management, featuring an improved basis for cost effective operations and future decision making in terms of e.g. life extension. The present paper deals with application of the digital twin concept in marine operations where it is essential to handle the inherent uncertainties of vessel performance by applying a model that can adapt to the real operating conditions. In this paper a case study is presented for identifying the most sensitive parameters in the vessel hydrodynamic model w.r.t. the vessel motion RAOs. The study also shows that the parametric sensitivity depends on the interesting vessel response parameter, wave direction and loading condition. A digital twin adaptive to various operational conditions may require parametric tuning of the numerical model. It is important to identify the correct parameter(s) for modification. A simplified and idealized case study is also carried out to test the requirements to a successful parameter identification for model tuning.
Structural Integrity Management (SIM) via a Digitalized Structural Integrity Compliance System
Authors: Ng Sok Mooi , Isnadi Biramarta , Lee Luong Ann , Omar Syahnaz , Saminal Siti Nurshamshinazzatulbalqish , Wan Shafie Wan Hariz Fadli , Khan Riaz 
Published: December 2020

Abstract
The objective of this paper is to present the digitalization of Structural Integrity Management for PETRONAS, via a web-based Structural Integrity Compliance System (SICS). Developed initially as a software application to manage the vast database for integrity management of offshore fleet, the system covers the substructure, topside structures, onshore civil and structural assets and ship-shaped floating structure modules.
The system is developed in line with API RP 2SIM, taking the SIM process of Data-Evaluation-Strategy-Program. The Data captured in the system inclusive of the design, construction, characteristics, inspection, foundation and metocean data required for evaluation of the likelihood of failure. While the life safety, environmental pollution & business loss data is assigned to evaluate the consequence of failure. After successful implementation of substructure module, the system has been expanded to capture data and evaluate risk of other types of assets, namely the topside structures, onshore civil and structural assets and at last, a module developed for a ship shaped floating structure.
A centralized database to manage the integrity a large aging fleet provides good visibility to the management in order to prioritize resources (budget, manpower and logistic) for inspection and maintenance, at the same time reducing the risk of operation disruption due to non-compliance. The system has created much cost saving through Risk-Based Underwater Inspection (RBUI) and risk-based anomalies repair.
SICS consists of the risk ranking sub-module and also other decision making tools including Strengthening-Modification and Repair (SMR) Toolkit, and Technical Limits Weight Control (TLWC) Tool. These toolkits are codified to provide quick decision making to management to evaluate the feasibility of SMR scheme or modification involving additional topside weights.
Thruster Performance of an Azimuth Stern Drive Tug
Authors: Yiew Lucas J. , Jin Yuting , Zheng Yingying , Magee Allan R. 
Published: December 2020

Abstract
The development of an accurate digital performance twin of a tug requires a complete understanding of its propulsive capacity and hull-thruster interactions. In this study, the propulsion characteristics of an Azimuth Stern Drive (ASD) tug is investigated using model-scale Reynolds-averaged Navier-Stokes (RANS) simulations. The propulsion plant consists of two counter-rotating thruster units, with each having a Ka4-70 series propeller and 19A duct profile. Comparisons in propulsive performances using the steady-state moving reference frame (MRF) approach and the transient rigid body motion (RBM) models are shown, and validated against data from openwater experiments. The MRF method gives sufficiently accurate predictions of thrust and torque in forward flow and moderate angles-of-attack, while the RBM method performs better at larger inflow angles. The effects of thruster-hull and thruster-thruster interactions on wake characteristics and propulsion performance are also investigated over a range of advance and inflow/azimuth angles. Convergence and mesh independence studies are conducted to determine the optimal spatial and temporal simulation parameters. Results from this study identify flow regimes where hull and thruster interactions are significant.
Numerical Simulation of Motion Response of Multi-Floating Body System Considering Different Gap Between TLP and TAD
Authors: Zhang Zhigang , Bao Shanjun , Ding Zhaogang , Wei Zhiyuan , Sui Haibo , Kang Zhuang 
Published: December 2020

Abstract
Tender-assisted drilling system meets the strict requirements of deck space of the drilling platform, and provides a relatively safe and comfortable working environment for the staff, which has been widely used in drilling operations in recent years. The significant difference between multi-floating body and single offshore platform is that there may be risk of collision between the floating bodies under extreme metocean conditions or in emergency of mooring system failure. In order to prevent the collision during drilling operations, the initial gap between floating bodies should be designed carefully and provide a reasonable scheme to ensure the safety of the drilling system and the feasibility of drilling operations. Therefore, based on the three dimensional potential flow theory, frequency domain and time domain numerical simulation of the motion response of TLP and TAD is carried out according to the marine environment of West Africa with extreme metocean conditions, the effect of different initial gap on the motion performance of floating bodies is explored and the mechanical characteristics of the mooring system are analyzed. Thus, the reasonable initial gap between TLP and TAD is determined by comparing the simulation results. In general, the numerical simulation results of tender-assisted drilling system may provide reference for engineering practice to some extent.
A New Higher-Order Euler-Bernoulli Beam Element of Absolute Nodal Coordinate Formulation
Authors: Zhang Peng , Ma Jianmin , Duan Menglan 
Published: December 2020

Abstract
In this study, a new higher-order Euler-Bernoulli beam element of Absolute Nodal Coordinate Formulation (ANCF) is developed for geometrically nonlinear analysis of planar structures. The strain energy of the beam element is derived by applying the definition of the Green–Lagrange strain tensor in continuum mechanics. The first contribution of this research is to realize the accurate calculation of curvature on the beam element node by additionally considering the second derivative of the position vector obtained by quintic Hermite interpolation function. Furthermore, in traditional theory, the independent variable of finite formulation is arc-length coordinate s, while in this work, a correction is come up with and proven that it is actually an equivalent parameter. Some benchmark problems of straight beams are solved by the proposed element and accurate results are obtained by just fewer elements when compared with the other works including the traditional ANCF element and B23 element of ABAQUS. What leads to this accuracy result is that the precise calculation of nodal curvature is obtained from higher order interpolation scheme. The correctness and accuracy of the proposed element are validated in this work and it can be further developed for tackling large deformation and large rotation problems of spatial curved beams.
Development of a Fluid-Structure Interaction Model of an Oscillating Wave Surge Converter Using OpenFOAM
Authors: Winter Andrew O. , Motley Michael R. 
Published: December 2020

Abstract
Wave energy converters (WEC), particularly those of the oscillating paddle type, are one of the least utilized categories of marine energy harvesting devices. As such, the goal of this research is to develop improved WEC technology through numerical modeling that will inform future experimental testing, which is being carried out by the Pacific Marine Energy Center. A novel scheme using mesh distortion and re-meshing to simulate the rotation of a wave-driven oscillating wave surge converter is presented herein using only the default functionality of the OpenFOAM computational fluid dynamics software package as a framework to implement the scheme as a convenient tool for engineers to study OWSC performance. This scheme relies on the use of finite volume mesh quality parameters, namely mesh cell non-orthogonality and skewness, to control when re-meshing operations are undertaken, minimizing the number of re-meshing operations needed to accommodate OWSC motions while maintaining solution stability and accuracy.
Numerical and Experimental Comparison of the Wave Response of a Very Light Floating Offshore Wind Turbine With Guy Wires
Authors: Shiohara Hiroki , Gonçalves Rodolfo T. , Houtani Hidetaka , Suzuki Hideyuki , Schnepf Anja , Hirabayashi Shinichiro , Carmo Lucas H. S. , Nihei Yasunori 
Published: December 2020

Abstract
A floating offshore wind turbine (FOWT) concept with a guy wire-supported tower was investigated to obtain results of motion in waves considering its elastic model characteristics. The FOWT concept aims to reduce construction costs by using a light-weight structure tensioned with guy wires and a downwind turbine concept type.
A wave tank experiment of an elastically similar segmented backbone model in the 1/60th scale was conducted to clarify the dynamic elastic response features of the structure. The results were compared with numerical simulations obtained with software NK-UTWind (in house software developed by the University of Tokyo) and WAMIT code.
It was clarified that the bending moment for tower and pontoons had two peak values when the response for each wave period was examined. The peak in the short-wave period was due to sagging when the wavelength matched the floater length. The other peak was due to the largest tower top acceleration, which caused a large bending moment at the tower base and pontoon to support the inertia force.
Attempt of a Real-Time Drilling State Identification With Machine Learning
Authors: Inoue Tomoya , Ishiwata Junya , Wada Ryota , Tahara Junichiro 
Published: December 2020

Abstract
Japan Agency for Marine-Earth Science and Technology (JAMSTEC) operates the scientific drillship Chikyu for scientific research. However, Chikyu has experienced problems with respect to drill pipe failure. This may be due to the limitation of indication of anomalies such as drill pipe failure in conventional drilling data monitoring.
As one of primary aims of scientific drilling is to recover core samples from sediment layers under the seabed, improving core recovery rate is very important because it can enhance the operation efficiency. Obtaining the information of lithology of drilling layer is also helpful for both scientific and operational aspects. However, there is no direct information regarding the core recovery rate and lithology. The recovery rate and lithology can be determined after retrieving a coring tool. Therefore, this study applies a machine learning technique to identify the drilling states, which includes anomaly detection of the drilling torque assuming the drill pipe failure, the prediction of core recovery rate as well as lithology.
This study aims to achieve real-time drilling state identification. Accordingly, a drilling data acquisition and distribution system was developed. The drilling data distributed from the system is read by data analysis systems in several languages for real-time analysis.
The drilling state identification models created in Python include the anomaly detection model and the prediction models of the core recovery and lithology. The models were installed in the real-time drilling data analyzing system, and real-time drilling state identification was attempted during the operation to confirm the health of the real-time drilling data analyzing system and to demonstrate identification with machine learning.