bluuebunny/crossref_metadata_2025_split huggingface dataset:
Parameter Sensitivity in Numerical Modelling of Ice-Structure Interaction With Cohesive Element Method
Authors: Feng Dianshi , Pang Sze Dai , Zhang Jin 
Published: October 2016

The increasing marine activities in the Arctic has resulted in a growing demand for reliable structural designs in this region. Ice loads are a major concern to the designer of a marine structure in the arctic, and are often the principal factor that governs the structural design [Palmer and Croasdale, 2013]. With the rapid advancement in computational power, numerical method is becoming a useful tool for design of offshore structures subjected to ice actions.
Cohesive element method (CEM), a method which has been widely utilized to simulate fracture in various materials ranging from metals to ceramics and composites as well as bi-material systems, has been recently applied to predict ice-structure interactions. Although it shows promising future for further applications, there are also some challenging issues like high mesh dependency, large variation in cohesive properties etc., yet to be resolved.
In this study, a 3D finite element model with the use of CEM was developed in LS-DYNA for simulating ice-structure interaction. The stability of the model was investigated and a parameter sensitivity analysis was carried out for a better understanding of how each material parameter affects the simulation results.
Engineering Establishment of Living Quarters for Jack-Up Rig Structures
Authors: Ha Yeong Su , Park Joo Shin , Koo Jeong Bon , Cho Byung Jin , Ma Kuk Yeol , Jang Ki Bok 
Published: October 2016

The Living-Quarters (hereafter referred to as ‘LQ’) is one of the major structures for ship and offshore structure. The LQ gives safe living conditions to crews on board. Until now the structural design of LQ structure is based on simplistic beam calculation to determine the initial scantling under design load. These days, safety for people is a raising issue. It is needed to meet the high oil company’s needs as well as technical specification throughout offshore project. But, the engineering procedure for LQ structure is not clearly defined by classification of society rules and international standards.
In this paper, the newly engineering procedure for LQ design is established considering LQ global loads with local loads for large equipment such as helideck structure, telecom mast and life saving appliances, and so on. To consider LQ global loads with local loads, the integrated three dimensional FE model and high technology engineering should be needed to require many kind of rules for equipment.
Recently, the damage of LQ structure is occasionally reported during towing condition for jack-up rig structure. The LQ of jack-up rig is encountered such as slamming pressure and greenwater produced by harsh wave loads during towing condition because of small height of freeboard comparing to the wave height. To verify the structural safety under towing condition, the detailed non-liner analysis is performed to verify the load-carrying capacity against greenwater pressure.
We newly propose a structural engineering procedure to improve the reliability of the LQ design in the jack-up rigs. From basis of this procedure, a more reasonable and optimized results are proposed as a practical manner as well as scientific approach.
Influence of the Draft Condition on Vortex-Induced Motions of a Semi-Submersible Platform With Four Square Columns
Authors: Liu Mingyue , Xiao Longfei , Lu Haining , Li Jun , Yu Xiaochuan 
Published: October 2016

The vortex-induced motions (VIM) phenomenon of semi-submersibles has drawn increasing attention with the development (mainly increase of column size) of new semi-submersibles. Due to the elongated submerged columns and the enlarged projected area to current, deep-draft semi-submersible platforms are susceptible to higher in-line drag forces and transverse vortex-induced lift forces, resulting in considerable horizontal motions in a current environment. In order to check the influence of draft conditions on VIM of the semi-submersible platform with four square columns, experimental investigations with five draft ratios varying from 0.87 to 1.90 were carried out in a towing tank.
The 6-degree-of-freedom (6-DOF) motions of the model were recorded by the motion acquisition system, in synchronisation with restoring forces provided by four load cells, one for each horizontal mooring spring. This paper discusses the dynamic behavior of a semi-submersible platform in five different draft conditions, including coupled motions at the water surface plane, drag and lift forces, and spectral analysis. It is shown that the largest transverse amplitudes are around 75% of the column width in the range of 6.0 ≤ Ur ≤ 8.0 for the deep-draft semi-submersible (H/L = 1.90). With 50% of the immerged column height of the deep-draft model, a 30% decrease in the transverse motion amplitude can be seen. Furthermore, the effects of the draft condition on yaw responses and current loads are also addressed.
The Study of a Possible Strengthened Structure Implanting Into the Hoses in Umbilical for Deep Water Application
Authors: Zhou Chongyao , Zhang Liang , Kang Yongtian , Qu Yan , Huang Kevin , Zhang Dagang 
Published: October 2016

Umbilical is the key actor connecting the subsea devices on the seabed to the platform, and acting like a neural line transforming the information from the central control system on platform to the subsea control elements.
Normally, according to the applied chemical reagent and hydraulics control fluid transmitting element, the umbilical is divided into two types for alternative depths, one consists with hoses for shallow water or medium water application, and the other utilizes the super duplex steel tubes for all depth water application. The main argument for using steel over thermoplastic hoses would be chemical resistance and hydraulic response time (where hose performance is poor).
However, the hose will have more flexibility than steel tube, which is also easier for manufacture. If the umbilical with hoses can be used in deeper water condition, the cost will decrease greatly.
In order to strengthen the hose structure for deep water use (up to 1000m twice the prior record), this paper will focus on the study of a possible strengthened structure implanting into the hoses to increase the outer pressure resistance capacity, which will increase the whole outer pressure resistance performance of umbilical finally. The thermoplastic hose with strengthened structure will enable the use of thermoplastic hoses in deeper water.
Loads and Dynamic Response of a Floating Wave Energy Converter due to Regular Waves From CFD Simulations
Authors: Büchner Anna , Knapp Thomas , Bednarz Martin , Sinn Philipp , Hildebrandt Arndt 
Published: October 2016

The commercial CFD code ANSYS Fluent is used for the three-dimensional estimation of wave loads and the dynamic response of a floating single point wave energy converter of the SINN Power wave power plant due to non-breaking and unidirectional waves in coastal waters. The VoF method is used to model the free surface and wave theories to set up the boundary conditions at the inlet for regular waves. The wave induced vertical motions of the floating module are computed by a sixDoF solver. Preliminary 2D and 3D studies to set up boundary conditions, mesh densities and solver settings were performed. The numerical results were compared to analytical solutions in form of water surface elevations and wave kinematics which showed good agreement.
The paper presents the dynamic response of the floating module for different load cases in terms of non-breaking waves. The resulting horizontal and vertical forces at the floating module will be presented and explained by the flow dynamics. Time and space depending velocities and pressure distributions including details on vortex separation will be given, which reveal valuable insights on the contribution of inertia and drag forces leading to the dynamic structural response of the floating devices.
Experimental Study of Wave Induced Loads and Motions on FLNG in Head and Oblique Sea Waves
Authors: Jin Yuting , Chai Shuhong , Duffy Jonathan , Chin Christopher , Bose Neil 
Published: October 2016

In the past decade, an innovative concept, the floating liquefied natural gas (FLNG) system has been developed as a more effective solution over conventional pipelines for exploiting offshore natural gas resources. Understanding the hydrodynamic behaviour of such a mega structure in a real seaway is essential for determining its performance as well as evaluating the operabilities of on-board facilities and safe offloading.
In this paper, experimental study on the hydrodynamic performance of a generic FLNG hull form has been presented. The 1:100 scale model was tested in the Australian Maritime College model test basin for head sea and oblique sea conditions at zero forward speed. The wave induced loads and motions were measured by load cells and linear variable differential transducers (LVDTs) respectively. Experimental uncertainties on each of the measured variables were studied by taking partial differentiations on the uncertainty sources. The time history measurements were decomposed by Fourier series for obtaining frequency domain force/moment and motion transfer functions. The results were compared with numerical solutions from potential flow and Reynolds-Averaged Navier-Stokes (RANS) solvers. A good correlation between the experimental and numerical results has been demonstrated.
Weather Window Analysis in Connection With Operation and Maintenance of Ocean Renewable Energy Devices
Authors: Taniguchi Tomoki , Ishida Shigesuke , Fujiwara Toshifumi , Inoue Shunji 
Published: October 2016

There is an increasing need for utilization of ocean renewable energy (ORE) around Japanese coast because Japan is surrounded by ocean. Because technologies for harnessing ORE have not been mature enough, Japanese government selects some demonstration sites for ORE devices and some demonstration projects are going. As these projects are progressed, the operation and maintenance (O&M) activities will increase and become essential factors for the success of demonstration projects. Hence, weather window analysis is required to quantify the levels of access for ORE devices in the demonstration projects, and commercial projects in the future.
In this paper, two new parameters are proposed in order to evaluate accessibility to ORE devices. One is the operational probability, and the other is the forecasted waiting time. The operational probability assesses weather duration with considering variability of wave condition. The forecasted waiting time is an expectation value of waiting time before O&M planners get next chance to arrange the O&M activities.
In order to check the effectivity of the proposed 2 parameters, accessibility is evaluated for significant wave height in terms of the 2 proposed parameters, these are
• Operational probability
• Forecasted waiting time
and 3 conventional parameters, these are
• Excess probability
• Persistence probability
• Waiting time between windows
The accessibility is evaluated at two locations along the Japanese coast.
This study reveals that large differences are caused between persistence probability and operational probability when operational wave height limit occurs intermittently and required window length is long. The forecasted waiting time has the same variation tendency as the waiting time between windows.
Impact of Water on the Fatigue Performance of Large-Scale Grouted Connection Tests
Authors: Schaumann Peter , Raba Alexander , Bechtel Anne 
Published: October 2016

Grouted connections represent a common joining technique between substructure and foundation piles of offshore oil & gas platforms as well as of offshore wind turbines. Due to cyclic loads arising from wind and wave actions the fatigue performance of the connection has to be considered. In lattice substructures like jackets the grouted connections are located at seabed level being fully submerged during their entire lifetime. Today’s fatigue design regulations are based on investigations neglecting any influence of the surrounding water since they were conducted in dry ambient conditions. So far, only Germanischer Lloyd gives additional recommendations for submerged grouted connections.
At the Institute for Steel Construction, Leibniz Universität Hannover, Germany investigations of the joint research project ‘GROWup’ focus on the fatigue performance of axially loaded grouted connections. The project is funded by the Federal Ministry for Economic Affairs and Energy (BMWi, funding sign: 0325290) and is the third project in a row dealing with grouted connections. As part of this research project, cyclic loading tests on small-scale and large-scale grouted connections with shear keys are conducted. Small-scale fatigue tests showed a reduced number of endurable load cycles for connections when tested in wet ambient conditions.
However, the transferability of these findings to a larger scale was still doubtful due to unknown scale effects. Therefore, the impact of water on the fatigue performance was tested recently at large-scale grouted connections. Previous to the submerged large-scale grouted connection fatigue tests, similar test specimens were exposed to alternating loads at dry ambient conditions. Comparison of both large-scale test results under wet and dry conditions enable to estimate the influence of water on the fatigue performance of grouted connections. Reflection of the small-scale test results gives hints on the scale effect. Test preparation, test results and design recommendations are presented in the paper.
Automated Landing and Mooring in Deep-Sea Environment Using Suction Buckets for Unmanned Vehicles
Authors: Boeck Florin , Golz Matthias , Ritz Sebastian , Holbach Gerd 
Published: October 2016

Autonomous underwater vehicles (AUVs) depend primarily on electrical power. Monitoring the deep-sea ocean floor efficiently requires easily accessible recharging techniques. In contrast to conservative ship-dependent charging processes on the surface, the Subsea Monitoring via Intelligent Swarms (SMIS) consortium uses a seabed station (SBS) as a power supply for AUVs. This paper describes the fully automated secure landing procedure of the SBS followed by a ground mooring maneuver on sandy sediments or soft clays. The unmanned seabed station is equipped with various sensors for status detection and environmental observation. In order to control the freefall and grounding without endangering the valuable components, an innovative procedure was implemented. Once landed, the nearly buoyancy-neutral station is moored using down-scaled suctions buckets that are normally used in immobile offshore oil rig foundations.
Laboratory full-scale experiments in modified test tanks for different length-to-diameter ratios endorse the design process. The feasibility of landing, mooring and ascending techniques was proven in field-tests in the Baltic Sea and the Atlantic Ocean.
Estimation of Wave Loads due to Green Water Events in 10000-Year Conditions on a TLP Deck Structure
Authors: Pakozdi Csaba , Östman Anders , Ji Guomin , Stansberg Carl Trygve , Reum Ola , Ovrebo Stig , Vestbøstad Tone , Sorvaag Christian , Ersland Jon 
Published: October 2016

In order to provide qualitative and quantitative information on the hydrodynamics loads during green water events on a module on the deck of a TLP in 10000-year conditions, MARINTEK has carried out CFD simulations. This paper presents extreme wave events and corresponding hydrodynamics loads on the module which can be directly linked to the extreme events observed in model tests. This means that the simulated extreme events can be related to a probability of occurrence, found from the model test.
A prerequisite for the structural design is that reliable estimates of hydrodynamic loads during a green water event can be made. Measured time series of waves from existing model test data are compared with CFD generated synthetic numerical waves. The selection of steep wave events are based on two physical parameters: the wave crest height and the rise velocity (time derivative of the free surface elevation at a given location). These parameters are relevant for green water and corresponding loads. The comparison of the measured free surface elevation of the calibrated waves with the time series of the numerical waves, as well as the measured and simulated relative wave probes time series shows that the applied numerical wave events have similar physical conditions as those observed in the model test.
In a new procedure developed by MARINTEK one identifies observed steep wave events, which are similar to existing numerical wave events, instead of trying to reproduce measured events. This procedure reduces the computational time, as well as computational costs, to an industrially acceptable level.
Traditional load estimation is not able to provide such reliable detailed local load history for structural design purpose at areas exposed to wave impacts. Therefore, topside modules are currently not installed in such areas. This new procedure, where CFD simulates realistic breaking waves with coupling to structural analysis tools, offers new possibilities for the design of structures subject to risk of green water loading.
Neural Networks for Tubular Joint Optimization in Offshore Jacket Structures
Authors: Christiansen Niels Hørbye , Tang Benny Korsholm 
Published: October 2016

The use of jacket structures to support offshore installations has for a long time been a popular choice in places with appropriate water depths. In recent years the use of jacket structures as offshore wind turbine foundations has also attracted increasing attention and is becoming a feasible alternative to traditional monopile foundations.
One of the key challenges in jacket design is optimizing tubular joints in terms of fatigue resistance. As it is not practically possible to include detailed FEM joint models in global jacket models designers are forced to look for alternative methods to obtain realistic joint representations. This is done by calculating influence factors (INF) and stress concentration factors (SCF) to be applied to simplified models of relevant tubular joints in global models in order to achieve a realistic force flow in the structure. One simple and widely used method is to apply parametric formulas, e.g. those suggested by Efthymiou. However, these approximating formulas have a fairly limited validity range. Therefore, on complex joint the most reliable way to determine INF’s is by setting up refined FEM models of relevant joints and then subsequently using the calculated factors in the global model. This strategy is computationally demanding and hence, very time consuming, as a new detailed FEM analysis of the tubular joint must be conducted for each step in the optimization process.
The present paper demonstrates how this time consuming procedure can be avoided by use of artificial neural networks (ANN) trained to estimate INF’s on tubular joints. The neural network is trained on a pre-generated library of detailed FEM joint models and is then able to predict INF’s on joints that are not part of the library — and thereby providing a significant reduction in calculation time during the jacket/joint optimization process. The analysis is conducted on a typical joint on a three legged jacket structure. The joint is located on a jacket leg and has two incoming braces. Such a joint has a finite number of free design variables, e.g. chord diameter/thickness, brace diameter/thickness, brace angle, gap etc. Each of these free variables can be considered as a dimension in the joint design space. Having a sufficient number of FEM joint models in the library the neural network can be trained to recognize and predict underlying patterns in this design space. The method is demonstrated on a limited number of design variables but should easily be extended to cover all variables as the joint library is expanded to include all dimensions.
Progressive Collapse Analysis of a Medium-Rise Circular RC Building Against Blast Loads
Authors: Al-Salloum Yousef , Almusallam Tarek , Ngo Tuan , Elsanadedy Hussein , Abbas Husain , Mendis Priyan 
Published: October 2016

This paper investigates the vulnerability of a typical medium-rise circular RC building against progressive collapse as a result of blast generated waves. The building is an eight storied (including one story basement) commercial complex. The likely blast threat scenario was identified by qualitatively assessing the vulnerability of the critical elements of the structure. LS-DYNA was used for the finite element modelling of the structure. The study presents local model analysis of one of its circular columns for which fluid-structure interaction through Alternate Lagrangian Eulerian (ALE) element formulation has been employed. The concrete volume in the columns was modeled using 8-node reduced integration solid hexahedron elements.
The global model analysis was carried out to examine the overall response of the structure due to the failure of one of the critical columns. The building was modeled using beam and shell elements. The 2-node axial beam elements with tension, compression, torsion, and bending capabilities were employed to represent the RC beams and columns, whereas the four node quadrilateral and three node triangular shell elements were used to represent the core wall, floor slabs, retaining walls and facade. The column bases of the building were fixed at the level of raft slab. The results of the study are proposed to be used to control or prevent progressive collapse of RC buildings.
Background for Revision of DNVGL-RP-C203 Fatigue Design of Offshore Steel Structures in 2016
Authors: Lotsberg Inge , Fjeldstad Arne , Ronold Knut O. 
Published: October 2016

The recommended practice DNVGL-RP-C203 on fatigue design of offshore steel structures has been revised a number of times since it was first issued in 2001. The 2016 revision includes additional information on a number of items asked for by the industry such as: Residual stresses in tubular sections made from cold forming, S-N data for subsea application, change in validity of S-N curve in seawater with cathodic protection, relation between surface roughness and requirements for roughness for coating, S-N curves and stress concentration factors for fatigue assessment of pipelines, relation between fabrication tolerances and S-N curves in different types of structural details and hot spot stress analysis for rainflow counting.
The background for this is explained in the paper. In addition the paper includes some information on recommendations for fatigue design of single-sided tubular joints that was included in the 2014 revision of the Recommended Practice.