bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of Recent Parametric Trenched and Partially Embedded/ Spanning Pipelines With DNV-RP-F109 Load Reduction Design Curves
Authors: Griffiths Terry , Shen Wenwen , Xu Mengmeng , Leggoe Jeremy 
Published: August 2013

An extensive series of 2D CFD analyses of subsea pipelines with parametrically varying seabed profiles have been performed in the past two years. These cases feature variations on wave and current flow conditions with pipeline partial embedment or spanning which extend beyond the range of conditions which have been published to date. This paper presents a comparison of the reduction factors calculated from this work with DNV-RP-F109 load factors and previous published research.
At present, the DNV-RP-F109 partial embedment / trenched pipeline load reduction factors are applied in both absolute stability analysis and also as a reduction factor on hydrodynamic force-time histories used in dynamic stability analysis. The suitability of this load factor reduction for dynamic stability analysis will also be considered.
In addition, a limited number of cases have been constructed in 3D which provide some initial insights into the variation of hydrodynamic loads across a pipeline span as a function of finite span length, enabling the validity of applying the 2D DNV load reduction factors across a 3D span to be considered. The 3D cases also consider inclined attack angles, and the effect they have on hydrodynamic forces across a span.
Measurement of Bending Residual Stress on a Hull Section of a Submarine
Authors: Ficquet Xavier , Bowman Ashley , Goudar Devkumar , Körner Manuel , Kingston Ed J. 
Published: August 2013

Explicit understanding of the residual stress field of primary submarine pressure hull induced during fabrication will improve the fidelity of numerical analysis and experimentation. Hence, supporting operational envelope and design life extension initiatives.
The fatigue lifetime of a submarine hull depends on the loads generated by hull contraction under the effect of hydrostatic pressure and the residual stresses existing in the absence of external loading. The use of numerical simulation allows a straightforward calculation of the stresses induced by the hydrostatic pressure. The effect of residual stress could be determined using the current failure assessment procedures, like BS7910 and R6. However it is more intricate to determine the residual stresses resulting from the sheet bending process combined with the sheet assembly using a multipass welding process.
There are several measurement techniques available to measure residual stresses. They are often classified by their level of destructiveness and their penetration.In order to compare the different measurement techniques an elastic-plastic bent beam sample has been chosen as it is very comparable to the residual stress field induced during the sheet bending process used in the submarine structure. Four bent beams have been measured using five different techniques: Incremental centre hole drilling, ring core, neutron diffraction, slitting and deep hole drilling technique. The results from measurement techniques show an excellent agreement when compared with the FEA.
In order to measure a full scale Rubis class submarine hull a limited number of techniques can be used, as the technique needs to be portable. The Deep Hole Drilling (DHD) technique was chosen because the neutron diffraction would require extracting a small test sample of about 400mm × 400mm, hence redistributing the residual stresses that were intended to be measured. Six measurements were carried out at different angular positions to detect variability in manufacture on a Rubis class submarine and a probabilistic calculation was done using all six DHD measurements. The Rubis class measurement results are also compared with two other submarine types, found in the literature.
Understanding the three-dimensional behaviour of residual stress in this type of structure provides a valuable resource to the numerical modelling community. The results can also support fatigue and fracture experimental work and may help increasing the operating life of 28 year old French nuclear submarine.
Irregular Wave Simulation and Fatigue Damage Evaluation of a Flexible Riser Subjected to Bi-Modal Sea States
Authors: Tan Zhimin , Hou Yucheng , Zhang John , Sheldrake Terry 
Published: August 2013

This paper presents the fatigue evaluation of a flexible riser subjected to bi-modal sea states, where the local wind and swell conditions act simultaneously, and is observed in many offshore regions including Brazil and West Africa. Due to the irregularity of the riser responses, the traditional, regular wave approach for assessing the fatigue damage of a flexible pipe cannot be applied without significant simplifications. A typical deviation would be to treat the combined swell and wind conditions at sea as two sets of separate cases. The regular wave approach can then be applied and the summation of the damage of both cases defined as the final damage of the pipe.
As an alternative, this paper presents a more theoretically accurate irregular wave approach. The entire irregular wave simulation was first performed using the commercial software, OrcaFlex™, together with a tensile wire stress model developed in-house. The model implements the pipe bending hysteresis behavior during dynamic excitation, producing corresponding time history stress results, which are used to assess the fatigue damage using a rain-flow counting method. Two case studies are presented, the first being a dynamic simulation performed with two wave trains generated based respectively on the given swell and wind sea spectrums. In the second case study, a single wave train is generated based on the combined spectrum of the swell and wind sea states. Both results are compared with those obtained by the traditional regular wave approach and a preferred analysis method is recommended based on the conservatism and time efficiency.
Current Loads on Net Panels With Rhombic Meshes
Authors: Enerhaug Birger , Føre Martin , Endresen Per Christian , Madsen Nina , Hansen Kurt 
Published: August 2013

In this paper, hydrodynamic load models applicable to rhombic net structures are discussed and compared to experimental results with net panels in steady currents. Net panels with mesh sizes and mesh opening angles as is commonly used in fishing gear, were tested in the SINTEF operated flume tank in Hirtshals, Denmark. Drag and lift forces acting on the net panels were measured in two different water currents with attack angles ranging from 0 to 90 degrees.
These measurement data were used as a benchmark to compare the performance of several established mathematical models of hydrodynamic loads on panels. Subsequently, an element-based approach with summation of lift and drag forces acting on all the individual twines of the element was performed, and the output from the simulations was compared with experimental data. The correspondence between results from the numerical simulations and experiments were in general quite acceptable for higher angles of attack, while the lack of a wake model overestimated the drag at lower angles. Lift was predicted with high accuracy for all panels.
Best Practice Guidance for Evaluating Knock-Down Factors in Corrosive Environments
Authors: Holtam Colum M. , Schneider Charles R. A. , Slater Graham 
Published: August 2013

The term knock-down factor is commonly used to describe the reduction in fatigue life in a corrosive environment (e.g. sour service) compared to performance in air. However, the mere concept of such a reduction factor is potentially misleading, particularly when comparing different welding procedures that demonstrate different in-air performance. This paper examines the concept and calculation of so-called knockdown factors.
To demonstrate the performance of girth welds in a corrosive environment, strip fatigue tests are conducted in air and in a simulated service environment, to determine an appropriate knock-down factor, which is then applied to the base design curve. However, there are a number of ways that such knock-down factors can be calculated, with different degrees of conservatism. For example, two different welding procedures may exhibit a different fatigue performance in air, but a similar performance when tested in a sour environment. The better performing weld (in air) is therefore assigned a greater knock-down factor, and possibly a more stringent sour design curve. In other instances, fatigue performance in air may significantly exceed that required. The determined knock-down factor, between strip tests in air and in a sour environment, can then be very large. Applying this reduction factor to the design curve results in a very stringent sour design curve, and may penalize the use of a girth welding procedure that results in good in-air fatigue performance.
There are no explicit, published guidelines for calculating corrosion fatigue knock-down factors. This paper describes an approach, based on experience and considering best practice guidance for the statistical analysis of fatigue data obtained from welded joints. The method is demonstrated using published sour corrosion fatigue endurance data, evaluating both mean and design curves.
Large Diameter, Deep Water PLEM Concepts
Authors: Damsleth Per , Abdalla Basel , Tang K. C. 
Published: August 2013

The export of gas from deepwater production systems can involve a large diameter pipeline with a manifold (PLEM) at the deep end. The PLEM commingles the flow from multiple smaller diameter risers, or flowlines, isolates the pipeline and provides a subsea pig launching and receiving facility. Connecting the PLEM to a large diameter (36” to 46”) gas export line is a major challenge because of the very stiff pipe. Horizontal diverless connection systems can align the pipeline terminations using powerful hydraulic jacks but the size and weight of the spools and equipment for such large diameter tie-ins make them difficult to handle. Therefore, modular designs on a sliding foundation have been developed which significantly reduce the energy required to make up the connection as well as facilitate maintenance and repair.
This paper describes the design aspects of large deepwater PLEM and the methodology which has lead to feasible solutions in 300m to 1300m water depths. Potential cost savings are related to successfully perfoming the subsea tie-ins using smaller subsea construction vessels. The deepwater connections become increasingly expensive for larger diameter pipelines if the risks are not reduced by the design and by performing advanced engineering involving finite element analysis (FEA).
Fully Coupled Time Domain Modelling of 3D Floating Bodies and Mooring Systems in Regular and Irregular Sea States
Authors: Vepa Kameswara S. , Van Nuffel Diederik , Van Paepegem Wim , Degrieck Joris 
Published: August 2013

Research on floating bodies like Wave Energy Converters (WECs) and Laser Imaging Detection And Ranging (LIDAR) systems has recently known a large growth. To study the minute details of the working model, it is important to study the effect of interactions between the waves, floating bodies and the mooring systems that are controlling the motion of the floating body. To achieve a more realistic numerical model in the time domain, a number of programs are linked together. The idea is to use the strength of each individual program for better results and also reduce the computational time.
This paper provides a solution in the direction of using a fully coupled time domain coupling code that controls the data flow between a fluid solver, a structural solver, and a kinematic system simulator.
Two- and three-dimensional fully coupled models are studied for calculation times and accuracy of results, and scaling is tested through parallelization on a large HPC cluster. The time step size of the whole model can be controlled by the user. Calculation times and memory requirements vary largely based on the factors like: domain size, SPH particle size, material model used for the floating body and the mooring system, complexity of the mechanical system inside the floating body. As a test case, a rigid body model is presented in this paper.
Modeling the Dual Crane Lift of Maersk BD Module
Authors: Aboumalwa Mohamed , Joe-Joe Chellakat , Nair Sajith 
Published: August 2013

McDermott Middle East, Inc. executed the Maersk Oil Qatar Project in 2009, Offshore Qatar. The project involved the installation of one of the heaviest lifts in the region — the 3283 MT BD Module. The deciding factor for the offshore installation methodology was the restriction on the lift capacity of the derrick barge. The execution strategy, therefore, involved utilizing two derrick barges, a semi-submersible and a mono hull barge, in tandem for the lift operation (Dual Lift). This paper discusses the engineering studies and the simulation model for a Dual Lift with insight into the technical complexities and the analytical strategy used for the study.
On site adherence to the engineering analyses was achieved by a system of pre-installed motion sensors and instruments capable of delivering real time data of the key parameters required for the lift. The engineering and operations experience presented in this paper covers the Dual Lift operation with focusing on two main engineering aspects, the engineered lift study of BD Module and the multi-body mooring analysis compromising six floating bodies connected together by means of lashing and/or mooring lines.
A Novel Concept of Flexible Pipe End Fitting: Tensile Armor Foldless Assembly
Authors: Campello George , Bertoni Fabiano , de Sousa José Renato M. , Carpigiani Marcos , Vardaro Eduardo , Mudry Guillermo 
Published: August 2013

The structural behavior of the flexible pipe tensile armors inside the end fitting (EF) is different from the one observed in the pipe body. The actual design methodology shows that the end fitting of the riser top section (at the interface with the floating unit) is critical with respect to fatigue, as stress concentration that occurs in this region during the end fitting assembly leading to significant plastic strains.
Aiming at improving the structural performance of flexible risers, Petrobras designed and patented a novel concept of flexible pipe end fitting in which its assembly can be carried out without the need of folding the tensile armor thus avoiding the introduction of plastic strains and residual stresses in this layer.
In order to assess and quantify the benefits of this new concept, in this work, a comparative study between the current end fitting concept used by the industry and the new technology proposed by Petrobras was conducted. This study comprises not only the stress distribution along the wire inside the end fitting but also the fatigue performance. For this purpose, finite element analyses have been carried out considering the entire end fitting mounting process and also the operational loads.
These analyses were calibrated with results from midscale tests in which a longitudinal slice of the real end fitting was simulated. An instrumented tensile armor wire was embedded in the resin epoxy and pulled out from a test device.
The results obtained show that the using of the proposed technology results in a considerably end fitting fatigue performance improvement.
Modeling of the Collapse and Propagation Behavior of UOE SAW Pipes Under External Pressure: Influence of Thermal Treatments for Typical Coating Applications
Authors: Mantovano Luciano O. , Serebrinsky Santiago , Ernst Hugo A. , Perez Teresa , Valdez Martin , de Souza Marcos , Chad Luis C. 
Published: August 2013

Large diameter UOE pipes are being increasingly used for the construction of offshore pipelines. Since oil discoveries are moving towards ultra deep water areas, collapse resistance is a key factor in the design of the pipelines. It has been demonstrated in previous works that the application of typical coating thermal treatments increases the collapse resistance of the pipes recovering the original strength of the plate. To improve the understanding of these effects, the Tenaris has embarked on a program of both, experimental testing and finite element modeling.
Previous phases of this work formulated the basis for model development and described the 2D approach taken to model the various stages of manufacture, from the plate to the final pipe and the collapse test. More recent developments included some modeling enhancements, sensitivity analyses, and comparison of predictions to the results of full scale collapse testing.
In the present work, 3D finite element analyses of collapse were performed and compared with the latest collapse and propagation tests performed by Tenaris, where the effect of typical coating thermal treatments was studied and significant increments in the collapse pressure of pipes were obtained. The numerical results show a good agreement with the experimental ones and could predict the increment produced in the collapse pressure by the effect of the thermal treatments. Comparison of the results with the predictions from API RP 1111 and DNV OS-F101 equations was also performed.
The outcomes of this study will be employed to further optimize the collapse resistance of subsea linepipe in order to reduce material and offshore installation costs through the increment of the fabrication factor as stated in the DNV OSF101 standard.
Methodology for Wind/Wave Basin Testing of Floating Offshore Wind Turbines
Authors: Martin Heather R. , Kimball Richard W. , Viselli Anthony M. , Goupee Andrew J. 
Published: August 2013

Scale model wave basin testing is often employed in the development and validation of large scale offshore vessels and structures by the oil and gas, military and marine industries. A basin model test requires less time, resources and risk than a full scale test while providing real and accurate data for model validation. As the development of floating wind turbine technology progresses in order to capture the vast deepwater wind energy resource, it is clear that model testing will be essential for the economical and efficient advancement of this technology. However, the scale model testing of floating wind turbines requires one to accurately simulate the wind and wave environments, structural flexibility and wind turbine aerodynamics, and thus requires a comprehensive scaling methodology.
This paper presents a unified methodology for Froude scale testing of floating wind turbines under combined wind and wave loading. First, an overview of the scaling relationships employed for the environment, floater and wind turbine are presented. Afterward, a discussion is presented concerning suggested methods for manufacturing a high-quality, low turbulence Froude scale wind environment in a wave basin to facilitate simultaneous application of wind and waves to the model. Subsequently, the difficulties of scaling the highly Reynolds number-dependent wind turbine aerodynamics is presented in addition to methods for tailoring the turbine and wind characteristics to best emulate the full scale condition. Lastly, the scaling methodology is demonstrated using results from 1/50th scale floating wind turbine testing performed at MARIN’s (Maritime Research Institute Netherlands) Offshore Basin which tested the 126 m rotor diameter NREL (National Renewable Energy Lab) horizontal axis wind turbine atop three floating platforms: a tension-leg platform, a spar-buoy and a semi-submersible. The results demonstrate the methodology’s ability to adequately simulate full scale global response of floating wind turbine systems.
Practical Considerations for the Structural Analysis of Offshore Topside Structures Under Gas Explosion Accidents
Authors: Han Dae Suk , Kim Gyusung , Sim Woo Seung , Jang Young Sik , Shin Hyun Soo 
Published: August 2013

Gas explosion accidents have been recognized as a major hazard of offshore facilities in oil & gas industries. Due to the nature of offshore topside structures, even a single collapse of structural members or equipments may lead to enormous economic and environmental losses. Therefore, such potential hazards that cause the accidental collapse need to be evaluated closely. Gas explosion has been categorized as an important issue of the design of offshore structures regarding the severity of the accident.
This paper presents practical considerations for the nonlinear dynamic structural analysis of offshore structures under blast loadings from gas explosion accidents. Numerical investigations including modeling of blast loads and idealization of structural materials and members have been conducted for the overall topside structures. As a design step for offshore structures under blast loadings, an applicable guidance on the finite element analysis (FEA) is described in this study.
Analysis of Stress Levels and Indication of Ruptures of Flexible Pipes Tensile Armor Wires During a Fatigue a Dynamic Tension to Tension Test
Authors: Lopes Diogo , Souza Italo , Falcao Gelson , Clevelario Judimar , Sheldrake Terry 
Published: August 2013

Flexible pipes are widely used in the exploration of oil at ultra-deepwater depths due to their properties of resistance to bending forces and ease of installation, compared to rigid pipe lines.
For each specific service application, several tests are required to qualify the flexible pipe’s design. One of the most important is the dynamic tension to tension test, the purpose of which is to qualify the end fitting assembly procedure and evaluate the design methodology used to predict the pipe’s service life.
During the development of the test, several sensors were fitted to the pipe sample to monitor the behavior of the armor wires. In order to monitor this test and identify any possible failure of the tensile armor wires, strain gauges were applied to all the wires of the external tensile armor layer in the area outside of the end fittings. Additionally, strain gauges were also applied to some of the internal and external tensile armor layer wires inside the end fittings. Other sensors, such as inclinometers and a tri-axial accelerometer were also applied to the pipe sample.
Analyses of the signals from the test sample instrumentation enabled detection of rupture of the tensile armor wire while instrumentation redundancy confirmed the tensile armor wire’s failure.
This paper presents the methodology used to identify the first 5 tension armor wire ruptures, which were identified by some of the sensors, i.e., the accelerometer, the inclinometer, and the strain gauges together with a comparison of the data of all the wire ruptures during the test.
Collapse Estimation of Interlocked Armour of Flexible Pipe With Strain Energy Equivalence
Authors: Tang Ming-gang , Yan Jun , Wang Ye 
Published: August 2013

Deepwater environment brings unbonded flexible pipelines with collapse risk of interlocked armours, such as pressure armour and carcass. An effective and accurate prediction for collapse is required in design process.
This paper presents a theoretical approach for estimating collapse of the interlocked armours based on strain energy equivalence principle of representative volume method. The strain energy with Dirichlet boundary is calculated using FEA software for the armours, which usually have complex cross-section. Meanwhile, an equivalent ring model is established as the representative volume, of which strain energy is acquired analytically. Equivalent thickness can be obtained by equivalence of both the two energys. And then the resistance to collapse of the flexible pipe can be carried out directly.
Theoretical results from the approach presented in the paper are compared with numerical results proved by experimental ones from reference, which verifies the equivalence approach. This approach provides a new angle to process parametric design for critical collapse of the flexible pipe.