bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Stress History and Shallow Embedment on Centrifuge Cone Penetration Tests in Sand
Authors: Roy Anamitra , Chow Shiaohuey , O’Loughlin Conleth , Randolph Mark 
Published: November 2019

Abstract
The paper investigates the effect of stress history and shallow embedment on centrifuge cone penetration tests in sand. A series of centrifuge cone penetration tests were performed in loose and dense silica sand at g-levels ranging between 20 and 100 with corresponding overconsolidation ratio (OCR) between 1 and 5. Based on the measured cone tip resistance (qc) profiles, improved empirical correlations have been proposed with depth factors (fD) to impart additional flexibility in accurately back predicting sand relative density (RD) at shallow embedment in normally consolidated (NC) sands. The qc - RD correlations are then extended to capture overconsolidation effects in cone tip resistance, which is broadly consistent with the changes in compressibility and in-situ lateral stresses taking place in sands with increasing OCR levels. The proposed expressions allow accurate quantification of depth corrected CPT profiles in soils of varying overconsolidation ratio, for application in the interpretation of model tests on shallow foundations and anchors and in shallowly buried structures such as pipelines. The expressions also have application for interpretation of field CPT profiles where the thickness of interbedded layers is of similar order of magnitude to the cone diameter.
Effect of Seabed Imperfection on the Buckling of Buried Pipelines Subjected to Wave-Induced Loads
Authors: Suresh Kumar D. , Sunny M. R. , Sahoo T. 
Published: November 2019

Abstract
Subsea pipelines operating under high pressures and temperatures are typically buried to protect from the environmental impacts and to prevent the instigation of global buckling. As the seabed profile is generally uneven, certain initial imperfections generally exist along the pipeline. As the pipe traverses in shallow waters, the seabed can be subjected to hydrodynamic loads caused by surface gravity waves. The hydrodynamic pressure, which typically depends on the wave height and water depth, leads to the development of pore pressures within the soil medium. This gradient of the pore pressures can cause significant uplift forces on the pipe, which may initiate the buckling in the vicinity of the imperfection. This study focuses on understanding the influence of these wave induced uplift forces on the buckling of the initial imperfect pipelines. Four typical imperfection profiles are considered in the study. The influence of imperfection shape on the buckling behavior is compared for surface laid and buried pipelines. Thereafter buckling behavior of the considered imperfect pipelines is studied with and without consideration of wave loads for a range of wave particulars and burial depths. The wave forces on the pipeline are estimated by solving Biot’s consolidation equations using finite element software COMSOL and the buckling studies are carried out using ABAQUS.
A Multipurpose Framework for Modelling and Simulation of Marine Aquaculture Systems
Authors: Su Biao , Reite Karl-Johan , Føre Martin , Aarsæther Karl Gunnar , Alver Morten Omholt , Endresen Per Christian , Kristiansen David , Haugen Joakim , Caharija Walter , Tsarau Andrei 
Published: November 2019

Abstract
Research within marine aquaculture has either focused on technology (e.g. farming structures, autonomous systems, harvesting and transport technologies) or biology (e.g. biomass control, feeding process, fish behavior and welfare). Here, we present a computational framework allowing the integrated analysis of these two aspects in a flexible and evolutive way. This framework is called FhSim which was originally developed for the modelling and simulation of fisheries operations and aquaculture structures, but its application domain has been continuously extended through different research projects.
In this paper, we present the basic design principles and functionality of the FhSim framework with the focus on modelling and simulation of marine aquaculture systems. The basic theories and methods used for the modelling of open net cages, closed cages, fish behavior, feeding processes, and ROV operations in net cages are introduced, respectively. It is also shown how the technological and biological aspects of fish farming can be considered in a specialized or integrated analysis. Furthermore, approaches for combining numerical models with monitoring sensor data, techniques for real-time simulation of fish farming operations and the coupling of FhSim with other simulation programs are discussed.
Influence of Mixed Flows on Ship Hydrodynamics in Dredged Channels
Authors: Terziev Momchil , Tezdogan Tahsin , Incecik Atilla 
Published: November 2019

Abstract
Although there is a significant body of research devoted to the shallow water hydrodynamic aspects of ships, several unexamined topics remain. Among these is that of critical outer flow in a dredged channel and its influence on parameters of interest. While empirical methods can be used with ease to resolve this, they can provide results with reliability sufficient only for an early design stage. On the other hand, more sophisticated potential flow theories are either inapplicable or do not perform well at the critical limit. However, RANS (Reynolds Averaged Navier-Stokes) – based tools can accurately capture all underlying phenomena without relying on limiting assumptions. This paper presents an attempt at comparing some results obtained via a CFD-based RANS solver and the slender body theory for critical outer flow in a dredged channel.
Study of Grouted Connections in Offshore Monopile Structures
Authors: Theotokoglou Efstathios E. , Papaefthimiou Georgia 
Published: November 2019

Abstract
In this paper the grouted connection (GC) of an offshore wind turbine is studied. The study is performed numerically by the finite element method (FEM). Initially, a description of the connection, its geometrical variations and its materials are presented. Moreover, analytical types about the deformation of the connection are presented. Subsequently, the analysis of the three dimensioned problem is performed numerically and the procedure as well as the parameters used, are given step by step. The case of the contact analysis problem is also studied. Practical issues such as mesh density and materials interaction are confronted. Finally, the stress state (SS) will be given in the analysis results, in order to specify the behavior of the connection under static loading.
Fatigue Life Assessment for Pipeline Dents Under Highway Crossings
Authors: Liu M. , Cross Colin , Brown Jason 
Published: November 2019

Abstract
A routine inline inspection pigging operation revealed a number of dent anomalies in an onshore pipeline transporting refined products. A detailed fitness for service assessment was subsequently performed by a leading engineering consultant company using the best industry practices, concluding that the dent defects with varying level of ovality in the order of 5% presented no immediate threat to the normal service under projected pressure cycles. The plain dent defect features were classified into a non-urgent category well down the scheduled repair list, requiring no priority intervention or replacement programme except further monitoring inspections and operating pressure control before a repair was planned. However, the dent defects in the proximity of highway crossings predicted to have longer remnant fatigue life failed unexpectedly within a much shorter time span, leading to costly emergency replacement and disruptive system downtime. This disparity has raised a question about the likely failure cause, uncertainty and reliability of the defect assessment. To this end, one anomaly was re-examined and its study is presented in this paper on how a fitness for service assessment for such dent anomalies can be improved using FEA modelling and consideration of some of the lessons learnt from similar failures and assessment experiences. It demonstrates that certain dynamic loading and additional fatigue promoting factors commonly ignored are of importance for fatigue life assessment.
Fatigue Crack Growth Rate Testing for Clad and Lined Pipe Girth Weld
Authors: Yang Zhengmao , Wu Youyou , Tronskar Jens P. , Xu Daqin 
Published: November 2019

Abstract
The Direct Current Potential Drop (DCPD) method is a common method used to detect the initiation of cracks, measure crack growth rates and monitor crack propagation. The method records total measurement of crack propagation, and can be used without visual accessibility, being suitable for special environments like high temperature, high pressure and sour service. Due to the discontinuity represented by the presence of a crack, when electric current flows through the component the crack size can be measured indirectly by the change of the electrical field. The potential difference can be related to crack size through experimental, analytical or numerical calibration curves. Analytical solutions are only limited to a small number of simpler geometries and homogeneous material. For clad and lined pipe, the clad/liner is stainless steel or nickel base alloys but the base pipe is carbon steel. The conductivities of the different materials are different. For lined pipe a small gap exists between liner and base pipe, this may change the electrical field around the root of girth weld. In this paper, finite element analyses are performed to generate the numerical calibration curves for the fatigue crack growth rate testing in sour service environment for clad and lined pipe girth welds. The method developed and described in this paper measures the fatigue crack growth rate for the crack located at the weld root which is in direct contact with the operating environment.
Experimental Investigation of Over-Trawlability of an Innovative Arctic Subsea Production Unit (SPU)
Authors: Wu Jie , Muthanna Chittiappa , Alsos Hagbart , Juhlin Rasmus , Karunakaran Daniel 
Published: November 2019

Abstract
Model tests have been performed to examine the overtrawlability of Subsea7’s Subsea Production Unit (SPU) in SINTEF Ocean’s Ocean Laboratory in November/December 2017. In this test campaign, 50 tests with different SPU orientations and trawling equipment were carried out. Two trawling water depth (100 m and 500 m) were simulated in the model test. Two types of trawl door, i.e. Thyborøn (5.5t) and Poly Ice (3.8t), with Selstad No. 620 type fishing net were used in present test. Overtrawling with a roller clump (7.6t) was also tested. Two trawling speeds of 1.6 m/s and 2.6 m/s and 5 SPU orientations were examined. Force measurements both on the fishing lines, and directly measured on the SPU were used to determine overtrawlability of the SPU. The dynamometer used in present test to measure the forces directly on the SPU is the first time that this type of measurement has been undertaken at SINTEF Ocean at the Ocean Basin facility with fully modelled trawling gear.
Uncertainty Analysis of Free Running Manoeuvring Model Test on a Modern Ferry, With Emphasis on Heel Angles
Authors: Kisjes Anton , Quadvlieg Frans , Ferrari Victor 
Published: November 2019

Abstract
This paper presents an uncertainty study on the manoeuvring behaviour of a twin screw ferry. In particular, we are interested in heel angles that this ship achieves while manoeuvring. Earlier published uncertainty analysis has focused on the uncertainty of overshoot angles and tactical diameters see [1] and [2]. The heel angles of these ships are not large. However, there is a class of ships that may encounter large heel angles due to steering. Ferries are such ships. The present paper quantifies also the uncertainty of the measured heel angles due to manoeuvres.
During the model test series, results are obtained for various values of the stability (GM), where large heel angles are observed. This provides a unique insight in the relation between the GM, approach speed, directional stability and the achieved heel angles. Because of the demonstrated large heel angles, it was important to make an uncertainty analysis of these tests. More publications have been written on the uncertainty of overshoot angles and dimensions of turning circle manoeuvres. However, the uncertainty of heel angles during manoeuvres hasn’t been published yet, which makes this a unique paper. The uncertainty analysis will be based on repeat tests for the zigzag 10°/10° and 35° turning circle manoeuvres. Repeat tests are carried out for these manoeuvres to verify the mean and the uncertainty of the experimentally obtained values. The methodology for estimating the uncertainty with 95% confidence bounds are derived by accounting for 1) uncertainty from measurement, 2) repeat tests and 3) the uncertainty from propagation of initial conditions and the error in check angle and rudder. The uncertainty results are compared with a previous study of uncertainty of manoeuvring characteristics of model tests with the KVLCC2 [1] and [2].
Vortex-Induced Vibration of a Flexible Cylinder Experiencing Oscillatory Flow With Different Aspect Ratios
Authors: Deng Di , Wu Lei , Wan Decheng 
Published: November 2019

Abstract
In deep sea oil exploitation, offshore platforms will move periodically in the water under the combined effects of waves, currents and winds. The relatively oscillatory flow is generated between the riser connected to the platform and the water. Vortex-induced Vibration (VIV) features of a single cylinder in the oscillatory flow are more complicated than that in the uniform flow. In this paper, numerical investigations on VIV of a flexible cylinder with different aspect ratios exposed to the oscillatory flow are carried out by the in-house CFD solver viv-FOAM-SJTU, which is developed based on the open source toolbox OpenFOAM. The flexible cylinder is forced to oscillate harmonically in the in-line direction in the still water and is allowed to freely vibrate in the cross-flow direction. Firstly, comparisons on referred experiments and simulations are conducted to verify the validity of the solver. Then, the modal decomposition analysis method and the Fast Fourier Transform (FFT) method are used to obtain the dominant vibration modes and frequencies of the cylinder in the following simulations.
A Broadband Array Signal Processing Method Based on Joint Sparsity of Signal Spatial Domain
Authors: He Daqian , Zhang Dahai , Wang Congying , Peng Xirui 
Published: November 2019

Abstract
Broadband underwater acoustic signal direction of arrival (DOA) estimation method is an important part of underwater array signal processing. The commonly used array signal DOA estimation algorithms due to the restriction of algorithm principles, are unable to process broadband array signal effectively, at the case of the arriving signals have strong correlation, small sampling snapshots or small arrival angle. Therefore, we need a new efficient algorithm to meet the increasing demand of broadband under water acoustic signal processing method. This paper makes use of the broadband acoustic signal similarity of joint sparsity in signal spatial domain received by underwater sonar arrays, establishes the whole space grid covering all broadband frequency domain slices. On the basis, the global sparsity of each frequency domain slice is combined with sparse element extraction class algorithm. By integrating the energy of signal on each slice, the spatial sparsity of each slice is obtained, from which we can get the directions of the arriving broadband wave signals. Through the simulation analysis and experimental verification on lake, we can be see that: The SDJS algorithm improves the performance and signal processing capability of the algorithm compared with the traditional algorithms. Therefore SDJS algorithm has a widely range of research value and application space.
New Material Development for Offshore Mooring Chains: High Manganese Steel
Authors: Verma Neerav , Wasson Andrew , Li Zhen , Sidhar Harpreet , He Haiping , Jin HyunWoo , Jun HyunJo , Ozekcin Adnan , Ling Shiun 
Published: November 2019

Abstract
Oil and gas industry experiences indicate that corrosion and wear of conventional mooring chain is an issue, which can result in costly pre-emptive chain replacement in an offshore environment. There is a need to develop new material technologies with improved performance over conventional carbon steel mooring chains to improve chain reliability.
This paper summarizes the development work on one such material — High Manganese Steel (HMS). A version of this steel has been utilized for superior wear performance at oil sands operation in Canada. This paper describes details on HMS chemistry optimization and lab testing for mooring chain application. In addition, Gleeble experiments were carried out to understand HMS hot deformation behavior and weldability.
Development testing work on HMS material has shown promising results in terms of corrosion and wear performance, relative to carbon steel mooring chains.
Hydrodynamic Forces on Near-Bed Small Diameter Cables and Pipelines in Currents, Waves and Combined Flow
Authors: Griffiths Terry , Teng Yunfei , Cheng Liang , An Hongwei , Draper Scott , Mohr Henning , Fogliani Antonino , Mariani Alessio , White David 
Published: November 2019

Abstract
The on-bottom stability design of subsea pipelines and cables is important to ensure safety and reliability but can be challenging to achieve, particularly for renewable energy projects which are preferentially located in high energy metocean environments. Often these conditions lead to the seabed being stripped of all loose sediment, leaving the cables to rest on exposed bedrock where roughness features can be similar in size to the cables. As offshore renewable energy projects progress from concept demonstration to commercial-scale developments, new approaches are needed to capture the relevant physics for small diameter cables on rocky seabeds to reduce the costs and risks of export power transmission and increase operational reliability. These same considerations also apply to the cables and small diameter pipes — such as umbilicals — required by oil and gas projects located on rocky seabeds.
Recent experimental testing using the University of Western Australia’s unique Large O-tube has enabled the experimental measurement of hydrodynamic forces on small diameter cables and pipes in proximity to smooth and rough beds. The tested conditions extend well beyond the existing published parameter range including much higher KC conditions together with seabed roughness which is comparable in size to the diameter. The results provide design data of great relevance to the ongoing development of marine renewable and conventional oil and gas projects, especially on rocky seabeds. This paper presents a summary of the existing knowledge on the subject as a preface to preliminary test results and gives tentative conclusions on the likely outcomes from this work.
Critical Review of Early Age Cycling Effects on the Capacity of Pile to Sleeve Grouted Connections As Treated in ISO 19902
Authors: Merxhani Andi , Jensen Jacob Fisker , Caetano Joao , Christiansen Casper Klintø 
Published: November 2019

Abstract
The treatment of early age cyclic loading (EAC) on pile-sleeve grouted connections is one of the challenging problems encountered in the design of offshore jacket structures. ISO 19902 appears to be the only offshore structural design code that quantifies the strength de-rating due to EAC. However, the mechanism of EAC considered in the ISO standard is little understood. Main provision is that the strength reduction due to EAC is considered to be linearly proportional to the compressive strength of the grout. This provision is conservatively applicable for medium strength grouts. However, it is over-conservative when modern high-performance grouts are used, and it can be further argued that it actually loses its physical meaning. Thus, a further investigation into the mechanics of the problem is deemed beneficial in order to understand better its underlying mechanism.
Using existing experimental evidence and a simple mechanical model, it is shown that the EAC mechanism considered in ISO 19902 triggers the grout matrix failure mechanism of the grouted connections. This behavior is characteristic of segregating grout materials. The benefit of the approach followed is that it links the interpretation of EAC to the grout material properties. The phenomenon is then understood using methods and experimental results that are well established in concrete mechanics. After a comparison with existing experimental evidence on grouted connections and concrete members, it is suggested that the strength drop for the specific shearing mechanism is independent of the uniaxial compressive strength of the grout material.
Dynamic Response of a Conceptual Designed Articulated Offshore Wind Turbine
Authors: Li Yan , Liu Zheng , Tang Yougang , Zhu Xiyang , Zhang Ruoyu 
Published: November 2019

Abstract
Focus on the 75-meter-depth offshore area, an articulated buoy is proposed for supporting NREL 5 MW offshore wind turbine. Based on the optimization, the main parameters are set for better hydro performance and less environmental loads. According to the quasi-static approach, the intact stability was examined. Then, an in-house code was programmed to simulate the dynamic response of the articulated offshore wind turbine. The aerodynamic load on rotating blades and the wind pressure load on tower are calculated based on the blade element momentum theory and the empirical formula, respectively. The hydrodynamic performance is simulated by the 3-D potential flow theory. The motions of platform, the loads on the articulated hinge and the power generation performance are documented in different cases. According to the simulations, the articulated offshore wind turbine shows good hydrodynamic performance under operation conditions.
An Analytical Approach for Predicting the Collapse Pressure of the Flexible Risers With Initial Ovalization and Gap
Authors: Li Xiao , Jiang Xiaoli , Hopman Hans 
Published: November 2019

Abstract
A flexible riser is a flexible pipe that transports materials between seafloor and topside structures. As oil and gas production heads to water depths greater than 3000 meters, huge hydrostatic pressure may cause the collapse failure of flexible risers. Generally, the collapse strength of a flexible riser is designed by considering the effects of initial imperfections, e.g., ovality of the carcass, and radial gap between the carcass/liner and pressure armor. These two imperfections may cause a significant reduction in the collapse strength of flexible risers under the flooded annulus condition. However, there are few analytical models available in the public literature that could take those factors into account. In this paper, an analytical approach is presented to predict the critical collapse pressure of the flexible risers with initial imperfections. The analytical results were compared with the numerical simulation, which showed reasonably good agreement.
Wear Amount of Steel Structure in Ice-Infested Sea by Sliding Wear Test
Authors: Takeuchi Takahiro , Kioka Shinji 
Published: November 2019

Abstract
Surface rust layers of corroded steel of coastal structures is removed by sea ice action in winter, leaving bare mild steel. This phenomenon is repeated every winter, promoting wear due to increasing corrosion. Serious damage to training levees comprising steel-sheet-pile seawalls on the Sea of Okhotsk, JAPAN occurred earlier than expected, since large wear rates were not considered in their design. This paper proposes a simple method for estimating wear amount (thickness) per year based on wear rate in a steady (mild) wear region obtained from sliding wear tests. This wear thickness can thus be taken as an additional thickness for the expected lifetime of a structure, as a rational countermeasure to corrosion as a sacrificial layer.