bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of Wake Interaction of Oscillating Platform With Four Columns
Authors: Hirabayashi Shinichiro , Cicolin Murilo M. , Gonçalves Rodolfo T. , Assi Gustavo R. S. , Suzuki Hideyuki 
Published: November 2019

Abstract
The effect of wake interaction on the hydrodynamic force was experimentally investigated. A scaled platform model with four columns was subjected to a current in the circulating water channel with constant velocity. The diameter of each column was 75 mm, and the aspect ratio (defined by the ratio between the column draft and diameter) was 1.5. The spacing ratios, (defined by the ratio between the distance of column centers and diameter) were 3 and 4. The platform was forced to oscillate with different frequencies and amplitudes. Flow around columns was measured by using Particle Image Velocimetry (PIV). The difference of hydrodynamic forces on each column was discussed concerning the effect of wake interaction among columns.
Estimating Fracture Toughness From Charpy Data
Authors: Pisarski Henryk , Bezensek Bostjan 
Published: November 2019

Abstract
Circumstances arise when direct determination of fracture toughness, necessary for conducting Engineering Critical Assessments (ECAs), is not possible but Charpy data are available. These situations can arise, for example, when assessments are needed for existing equipment to demonstrate avoidance of fracture or preliminary assessments are required when only specification properties are available. Some of the empirical procedures that may be used to estimate fracture toughness of steels are described. These are based on a recent revision and update of Annex J of BS 7910; the latter provides an integrated method for conducting ECAs. Procedures for estimating fracture toughness from Charpy data representing lower shelf (energies less than 27J), transitional (based on T27J or T40J (Charpy temperatures for 27J or 40J, respectively)) and upper shelf Charpy behaviour are described. In addition, a method is described for estimating T27J when determining fracture toughness from transitional Charpy behaviour where an incomplete transition curve or only single temperature data are available. The thinking behind the procedures is described and examples for their validation (i.e. predictions of fracture toughness compared with actual data) are provided.
CFD for Vortex-Induced Motions and Line Forces of a Floating Caisson With Complex Geometry
Authors: Decrop Boudewijn , Kulkarni Rohit , Breugem Alexander , Villaverde Vega Damian 
Published: November 2019

Abstract
Two caissons with complex geometry need to be towed to an installation site in a straight with potentially strong currents, fairly strong wind and moderate wave conditions. In order to design the mooring system, current, wind and wave forces need to be assessed. Both time-averaged and oscillating components are important. A methodology in which the degree of complexity is gradually increased has been conceived. In this methodology, first an assessment of the order of magnitude of each force is determined, after which it is decided whether in-depth computation of higher accuracy is required. This led to a methodology in which wind forces have been determined analytically, current forces and Vortex Induced Motions (VIM) have been determined using CFD and wave forces by means of a panel method. The resulting forces have been combined in a numerical mooring analysis. The focus of the presented paper is on the CFD model applied to determine VIM and a comparison with resonance frequencies determined analytically.
Fatigue of Welded Tubular X-Joints in Offshore Wind Platforms
Authors: Papatheocharis Theocharis , Sarvanis Gregory C. , Perdikaris Philip C. , Karamanos Spyros A. 
Published: November 2019

Abstract
The paper is part of the European research program JABACO (2015–2018), on the optimization of design and construction of offshore jacket platforms for supporting large wind turbines (5–10 MW) in water depths ranging from 30m to 80m. In particular, the paper describes an experimental investigation on the high-cycle fatigue performance of welded tubular connections, subjected to in-plane bending loading. Experimental results from seven (7) X-joint specimens are presented. The specimens were manufactured with 18-inch-diameter tubes and a brace-to-chord-diameter ratio equal to 1. Furthermore, the brace-to-chord-thickness ratio is equal 0.6, and the brace-chord angle is 90-degrees. The specimens are made of regular carbon steel grade 355, and have been fabricated using two different welding techniques: (a) manual (semi-automatic) welding (5 specimens); and (b) robot (automatic) welding (2 specimens). The comparison of the fatigue design life of those welding methods is a major objective of the present study. Prior to testing, numerical simulations have been performed to determine the critical locations around the weld toe, for proper instrumentation of the tubular specimens in terms of strain gage locations. This research work aims at a critical evaluation of available design standards, towards the development of more reliable design tools and reduction of the construction cost of the platform.
Quasi-Static and Dynamic Compressive Behaviors of Closed-Cell Stochastic Foams Based on Voronoi Model
Authors: Chen Jianyong , Liu Jun , Cheng Yuansheng , Zhang Pan 
Published: November 2019

Abstract
Closed-cell stochastic foams are widely used in engineering field due to the excellent energy absorption capability. In this paper, the crushing response of three dimensional closed-cell foams is investigated under quasi-static and dynamic compression loading. Voronoi tessellation is employed to generate the mesoscale geometric models of closed-cell stochastic foams, and subsequently numerical analysis is carried out using LS-DYNA software. Results reveal that the plateau stress of Voronoi model under quasi-static compression linearly increases with the increase of relative density. In addition, the mechanical properties of Voronoi model under quasi-static and dynamic compression are related to a shear band collapse mode and a layer-wise collapse mode, respectively. The plateau stress and the densification strain under high-speed loading are higher than those under quasi-static and low-speed loading.
On the Hydrodynamic Interaction Between Ship and Free-Surface Motions on Vessels With Moonpools
Authors: Ravinthrakumar Senthuran , Kristiansen Trygve , Ommani Babak 
Published: November 2019

Abstract
Coupling between moonpool resonance and vessel motion is investigated in two-dimensional and quasi three-dimensional settings, where the models are studied in forced heave and in freely floating conditions. The two-dimensional setups are with a recess, while the quasi three-dimensional setups are without recess. One configuration with recess is presented for the two-dimensional case, while three different moonpool sizes (without recess) are tested for the quasi three-dimensional setup. A large number of forcing periods, and three wave steepnesses are tested.
Boundary Element Method (BEM) and Viscous BEM (VBEM) time-domain codes based on linear potential flow theory, and a Navier–Stokes solver with linear free-surface and body-boundary conditions, are implemented to investigate resonant motion of the free-surface and the model. Damping due to flow separation from the sharp corners of the moonpool inlets is shown to matter for both vessel motions and moonpool response around the piston mode.
In general, the CFD simulations compare well with the experimental results. BEM over-predicts the response significantly at resonance. VBEM provides improved results compared to the BEM, but still over-predicts the response.
In the two-dimensional study there are significant coupling effects between heave, pitch and moonpool responses. In the quasi three-dimensional tests, the coupling effect is reduced significantly as the moonpool dimensions relative to the displaced volume of the ship is reduced.
The first sloshing mode is investigated in the two-dimensional case. The studies show that damping due to flow separation is dominant. The vessel motions are unaffected by the moonpool response around the first sloshing mode.
Optimising Fracture Assessment of Welded Structures Using BS 7910, R6 and FEA
Authors: Hadley Isabel , London Tyler 
Published: November 2019

Abstract
The fracture clauses of BS 7910 and R6 present a hierarchy of assessment methods. Depending on the data available, the user may adopt the simplest approach (Option 1), or the higher Options (2 & 3), allowing increasing accuracy and decreasing conservatism. Additional assessment procedures are available via the Annexes of BS 7910 and via Chapter III of R6, which address the inclusion of welding residual stress, crack tip constraint, weld strength mismatch and warm prestress.
This paper illustrates the application of both basic and advanced fracture assessment procedures to a set of welded wide plate test data. The tests featured extensive materials testing, along with detailed characterisation of welding residual stress both in the as-welded condition and after a warm prestress treatment.
The study shows how the accuracy of the assessment increases as the more advanced assessment methods are employed. A tailored assessment of the uniaxial tests using elastic-plastic FEA was also carried out, allowing a comparison between the analytical formulae given in BS 7910/R6, numerical analysis and experimental results.
Experimental and Theoretical Investigations on the Characteristics of Ice Floes Broken by Ships Sailing Ahead in Level Ice
Authors: Myland Daniela 
Published: November 2019

Abstract
Although the hull shapes of modern ice breaking vessels seem to be quite similar at a first glance, there are significant differences in their ice breaking performance. A significant amount of research effort was spent on investigations of the icebreaking process and the resulting forces. However, little information is available on the correlations between ice floe characteristics, hull shape parameters, ice properties and the ice resistance. Thus, systematic model tests in level ice and pre-sawn ice with four icebreaking ship models of one ship type have been conducted to gain new insight on these correlations. During the tests in level ice under water video records have been taken from below the ship model. Video frames have been analyzed by application of a dedicated image analysis procedure which is mainly based on a number of semiautomatic scripts applied in Matlab®. Results of the analysis are presented and discussed within this paper.
Optimization Design of FPSO Central Cooling Water System Based on Pipe Network Fluid Analysis
Authors: Zhang Huan , Yuan Hongtao , Wang Chao , Kong Weiwen , Xu Jiangguo , Wang Zhaoqiang 
Published: November 2019

Abstract
Marine power generator plays important role to guarantee the normal operation of all subsystems of FPSO, in which cooling device are emphasized on its reliability and stability. As the main cooling system of FPSO power generator, the design of central cooling water system is very important. Traditional pipeline network system design is mainly based on the design manual and empirical formula, which single pipeline is designed for circulation of different media. Lacking the concept of system integrity, which results in the weak integrated design without rational consideration. In this paper, a FPSO central cooling water system is taken as the research object. Based on the initial design scheme, it is different from the empirical and singularity of traditional design, and the impact of the pipe network of cooling water system to that of other systems in the whole vessel is put into consideration on the comprehensive way. From the economic point of view, the study on the pipe network of flow balance is carried out, and the optimization scheme of the central cooling water pipe network system is proposed.
A 6-DOFs Hardware-in-the-Loop System for Wind Tunnel Tests of Floating Offshore Wind Turbines
Authors: Fontanella Alessandro , Bayati Ilmas , Taruffi Federico , La Mura Francesco , Facchinetti Alan , Belloli Marco 
Published: November 2019

Abstract
This article presents a hardware-in-the-loop (HIL) methodology developed at Politecnico di Milano (PoliMi) to perform wind tunnel tests on floating offshore wind turbines (FOWTs). The 6-DOFs HIL setup is presented, focusing on the main differences with respect to a previous 2-DOFs system. Aerodynamic, rotor and control related loads, physically reproduced by the wind turbine scale model, must be measured in real-time and integrated with the platform numerical model. These forces contribute to couple wind turbine and floating platform dynamics and their correct reproduction is of fundamental importance for the correct simulation of the floating system behavior. The procedure developed to extract rotor loads from the available measurements is presented, discussing its limitations and the possible uncertainties introduced in the results. Results from verification tests in no-wind conditions are presented and analyzed to identify the main uncertainty sources and quantify their effect on the reproduction of the floating wind turbine response to combined wind and waves.
Analysis of Mechanical Properties of Carbon Fiber Reinforced Spiral Rod in Umbilical
Authors: Zhang Yu , Cheng Ning-yi , Zhao Yi , Zhang Peng 
Published: November 2019

Abstract
Nowadays, the weight of steel pipelines restricts the development process of deep-water oil and gas. Using spiral carbon fiber reinforced rod instead of the steel armored layer in the umbilical can effectively solve the contradiction between carrying capacity and self-weight of the umbilical cable in the deep-water oil and gas development process. In this paper, using anisotropic carbon fiber materials, the stiffness matrix of the spiral carbon fiber reinforced rod under the tension-torsion coupled load is deduced through mathematical analysis and finite element calculation. It is found that the results of various stiffness coefficients obtained by mathematical analysis are closed to the finite element calculation. In addition, the integral form of carbon fiber reinforced umbilical is determined preliminarily, and the overall mechanical properties of umbilical are carried out. It is found that carbon fiber reinforced spiral rod in umbilical could have good mechanical properties with less weight.
Analysis of the Pitting Corrosion’s Effect on the Residual Strength of Submerged Pressure Shell
Authors: Xu Weijun , Chen Tianyi , Li Chenfeng , Zhou Xueqian , Liu Feng 
Published: November 2019

Abstract
Submerged pressure shell’s corrosion situation is more serious due to bad work environment, complex structure and difficulty of maintenance. Based on the analysis of calculation method of submerged pressure shell structures with non-corrosion, the calculation formula of pressure shell with pitting corrosion is given. The Finite Element Model is constructed and its residual strength is investigated. The relationships between shell stress and some parameters, such as radius of corrosion pit, depth of corrosion pit and location of corrosion pit are studied. Based on the finite element analysis results, the effect of radius of corrosion pit on the stress of pressure shell with pitting corrosion is analyzed. Furthermore, the influence coefficients of residual strength of pressure shell due to depth and location of pitting corrosion are determined, which provide a reference for the strength evaluation of submerged pressure shell with pitting corrosion.
Response Characteristics of a Floating Structure With Moon Pools Installed With Vertical Axis Wind Turbines
Authors: Nakamura Mitsuru , Ikoma Tomoki , Eto Hiroaki , Aida Yasuhiro , Masuda Koichi 
Published: November 2019

Abstract
This paper describes characteristics of motion responses and tether tensions of a floating structure with four moon pools, on which one or two vertical axis wind turbines are installed.
In this study, the authors proposed a twin-VAWT installed floating system, which was a pontoon based structure. However four moon pools were set on. The study conducted model experiments in a wave tank using regular waves with 0.6 to 2.0 seconds in wave periods and 0.02 and 0.04 m in wave height. The model had four moon pools and was installed with one or two vertical axis turbine models. From it, gyroscopic moment effects were investigated. Besides, the study performed numerical calculations with the linear potential theory based method which were a Green function method.
As a results, responses of the twin-turbine model are not affected by gyroscopic moment. The study discusses motion responses and tether tensions with nonlinear behaviours from mainly the experimental results.
Response Based Time Domain Structural Analysis on Floating Offshore Platform
Authors: Kyoung Johyun , Samaria Sagar , Kim Jang Whan , Duffy Brian 
Published: November 2019

Abstract
Performing the structural analysis and its integrity evaluation is the ultimate goal of design. However, design value estimation based on load-based analysis is still used as a conventional procedure in the offshore industry. The conventional method can be overly conservative and unrealistic with inconsistent load conditions since external loads such as mooring/riser and higher order hull response is inconsistently considered based on simplified linear assumptions. To assess the reliable integrity of a floating offshore platform, the response-based analysis has been successfully applied.
This paper presents a response-based time domain structural analysis of a floating offshore platform. Direct time domain structural analysis is applied by mapping of external environment loads on the floating platform at every instantaneous time interval. Accordingly, correct phase relationship between the various external loads and hull motion including nonlinear effects can be considered. For computational efficiency, present study uses a set of load components based on an efficiently selected basis function for hull motion and environment loadings. The stress time history is obtained directly by synthesizing the load components, and hence an actual time-domain structural response can be captured effectively. Thus, same structural analysis results can be used to evaluate both strength and fatigue criterion for a floating offshore structure.
Present analysis method is successfully applied to the evaluation of extreme global strength for a conventional semisubmersible platform. Present time domain analysis result on the structure response is compared with conventional load-based analysis result.
Trajectory Prediction of Moored Vessels With Reduced Station Keeping Capability due to Exceeded Anchor Load Limits
Authors: Josten Michał 
Published: November 2019

Abstract
This paper presents the development and application of an in-house manoeuvring method for the prediction of the track of a moored vessel in the case of a temporary or total loss of station keeping capability as a result of exceeded permissible anchor loads. The described method is implemented in the in-house ship design environment E4, which already contains a method for manoeuvring simulations. The equations of motion are solved for three degrees of freedom: surge, sway and yaw. Any effects due to dynamic heel are considered quasi-statically. The method is based on a force model with components for environmental and body forces as well as propeller, rudder and steering forces for dynamic positioning applications. For the purpose of mooring system analysis an additional force component for the mooring line loads is introduced by using load-deflection curves. These curves can be calculated within E4 or imported from other sources. The resulting method allows detailed response calculations in the time-domain and can be used in various applications due to its great computational efficiency. In the presented paper the method is used for the analysis of a marine casualty due to harsh weather conditions.
Numerical Simulation and Result Interpretation of Large Scale Fatigue Testing of Tubular X-Joint Close to Resonance Frequency
Authors: Thibaux Philippe , Van Wittenberghe Jeroen , Van Poucke Maarten 
Published: November 2019

Abstract
Fatigue testing of tubular joints is normally performed at a low frequency, making the tests typically very long. Recently, a new testing method has been developed where a specimen is excited close to its resonance frequency, making it possible to achieve testing frequencies higher than 20Hz. In the present investigations, different nodes representing an X-joint (diameter of the brace 711mm, wall thickness 20mm) were tested until failure in the resonance test set-up. The new testing method allows to load the full circumference of the weld with a nominal stress following an elliptic profile, such that the fatigue cracks can be initiated at many locations around the weld with similar probability of failure. The paper will present the strategy for the design of the specimen, aiming to achieve similar resonance frequencies for in-plane and out-of-plane bending and similar probability of failure along the welds. After reception of the specimen and testing, new finite element simulations were run and compared to the experimental response of the specimen. The influence of different aspect of the modelling will be discussed, with their influence on the identified resonance frequency and strain gauge readings. The investigation proves that it is possible to obtain a reasonably homogeneous hot spot values along the weld, resulting in the initiation of cracks not anymore dictated by the hot spot values, but by the local geometry of the weld.
Efficiency Assessment of the Composite Materials Repair Systems Intended for Corrosion Damaged Pipelines
Authors: Dumitrescu Andrei , Diniţă Alin 
Published: November 2019

Abstract
This paper presents the results of the research work carried out by the authors in order to evaluate the efficiency of the composite material wraps/sleeves (made of a polymeric matrix and reinforcing fabric) used to repair steel pipelines carrying hydrocarbons upon which local metal loss defects (generated by corrosion and/or erosion processes) have been detected. The pipeline repair technologies consisting of the application of composite material wraps are perceived as being advantageous alternative solutions for substituting the conventional technologies, which require welding operations to be performed in the pipe areas with defects.
The efficiency of the composite repair systems has been investigated by assessing the reinforcement effects (the restoration level of the damaged pipe mechanical strength) generated by the applied composite wraps as a function of their geometry and mechanical properties. To that purpose, numerical models based on finite elements have been developed and certified by comparing them with the results of several experimental programs previously performed by the authors. Finite elements simulations have also been conducted in the plastic region, taking into account material non-linearity.
The calculation methods proposed in literature (among which a method previously developed by the authors) to define the composite wrap dimensions (thickness and length) for a given pipe have also been investigated and compared to our numerical results in order to select the most adequate solution for the design of the composite repair system. The optimal values for the mechanical properties of the composite material used by the repair system have also been defined.