bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Attrition due to Water in Cyclically Loaded Grouted Joints
Authors: Schaumann Peter , Raba Alexander , Bechtel Anne 
Published: September 2014

According to political goals, electricity from offshore wind farms in Germany will amount to 15 GW by 2030. Most of the wind farms will be located far offshore in water depths larger than 30 m. For such water depths, lattice substructures like jackets or tripods are the preferred solution. The substructures are founded on piles and connected to these by submerged grouted joints. In lattice substructures grouted joints are predominantly loaded by cyclic axial loads. Even though, this connection is well known from the offshore oil and gas industry, comparatively few results on effects of attrition due to water for grouted joints are available.
At the Institute for Steel Construction of the Leibniz University Hannover, Germany, within the joint research project ‘GROWup’ investigations focus on the fatigue performance of grouted joints under predominant axial loading. As part of this research project, cyclic loading tests on small scale grouted joints with shear keys were conducted. The specimens were filled with industrial grout products and tested in a water basin to evaluate the influence of water to the fatigue performance of the connection at small scale. These test results show that the water effect leads to a significant reduction of the fatigue performance of the connection compared to results from tests in dry conditions. Moreover, the impact of water is proportional to the applied test frequency. The results of the structural tests differ from results of pure material specimen tests, on which current code provisions are based.
This paper presents results from the small scale tests on grouted joints with shear keys in dry and submerged conditions. Effects of attrition due to water are shown and their effect is quantified. The results are compared to other published findings. In conclusion the presented investigations underline the importance of the water effect to the fatigue performance of small scale grouted joints. In conclusion, this paper will stimulate discussions on the demand for research on large- and real-scale grouted joints.
Uncertainty in Stress Concentration Factor Computation for Ship Fatigue Design
Authors: Ogeman Viktor , Mao Wengang , Ringsberg Jonas W. 
Published: September 2014

In stress-based fatigue design and analysis of marine structures, a stress concentration factor (SCF) is used to compute the local stress in structural details when the hot-spot approach is used. For a typical steel material, the fatigue damage is computed as proportional to the power 3–5 of the stress values, defined by the chosen S-N curve. This means that a small change in the SCF value can lead to a large difference in the fatigue damage result and corresponding fatigue life prediction. Thus, the methodology used to compute the SCF should be clearly defined in classification society guidelines.
This study presents a review of different direct calculation procedures for how to obtain the SCF based on fatigue assessment guidelines. The effect of different element types and local stress extrapolation methods to the fatigue damage estimation is studied for both longitudinal load and bending load conditions in a container ship. A simple structural detail with cracks observed after only a few years in service is used for the case study. For this structural detail, two alternative methods to compute the local stress for fatigue assessments are compared. The difference in fatigue life prediction using the proposed approaches is compared; with at least 50% difference expected even within the guidelines from the same classification society. It is further discussed how to reduce the SCF with the objective to increase the fatigue life.
Comprehensive Qualification Program for the Browse 24 Inch High Temperature Flexible Joint Prototype
Authors: Mekha Basim , Hawkey Ben , Patrick James , Pottorff Todd 
Published: September 2014

Flexible Joints have been an essential part of many steel catenary risers (SCRs) as one of the main means for connecting SCRs to the floating facilities in deep water. Since 1994 when the first Flexible Joints were installed on the Augur Tension Leg Platform (TLP), many Flexible Joints have been designed and installed for 6 inch to 24 inch SCRs on all kinds of floating production facilities and in a range of water depths.
Woodside Energy Limited (Woodside), as operator of the Browse LNG Development on behalf of the Browse Joint Venture participants for their original Browse LNG Development concept (Browse to Kimberley subsea development and onshore processing concept), had contemplated using Flexible Joints as top termination units for the high temperature 24 inch Wet Gas Export SCRs. Woodside contracted Oil States Industries, Inc. (OSI) to design, manufacture and test a prototype 24 inch Flexible Joint that would meet the project’s stringent operational and fatigue requirements for 40 years design life. This high temperature 24 inch Flexible Joint was the largest Flexible Joint ever manufactured since its design required bellows and a thermal barrier.
A state-of-the-art qualification program for the high temperature 24 inch Flexible Joint was undertaken to demonstrate its feasibility for use on the 24 inch wet gas export SCRs for the Browse project in approximately 600m water depth. The Flexible Joint prototype was subjected to a comprehensive test program, including axial and rotational tests, hydrotests and a fatigue test, which was developed to cover all aspects of the Flexible Joint design and its components.
In this paper, the details of the high temperature 24 inch Flexible Joint qualification program will be presented with emphasis on the steps taken to successfully complete the program and the lessons learned from the challenges that were encountered. The paper will also provide a summary of the challenges and steps taken to complete the program which presented a unique opportunity to expand on the capability of the industry to go beyond what has been previously accomplished. The program was very challenging in all aspects but succeeded in achieving all of its goals.
Experimental Investigation of Steel Coiled Tubes Performance Under Cyclic Bending
Authors: Lagat Christopher , Roufail Reem , Rasouli Vamegh , Evans Brian , Soe Soren 
Published: September 2014

Research is currently being undertaken in Australia to develop new drilling technologies for deep mineral exploration. The Deep Exploration Technologies Cooperative Research Centre (DET CRC) has carried out a comprehensive review of the available drilling technologies in the market. Following the study, coiled tube drilling technology has been suggested as a faster and cheaper method than conventional pipe drilling. This is primarily due to its smaller footprint relative to the standard rotary method, ease of unit mobility, less operating personnel, faster rate of penetration, and faster rig up and rig down times. The steel coiled tubing technology has traditionally been used in the petroleum industry. While there have been several attempts to evaluate the performance of coiled tubes in the oil and gas industry, limited or no attempts have been made to assess its performance in deep hard rock mineral exploration drilling. Therefore, DET CRC is in the process of re-designing the coiled tube rig approach to enable fast and efficient drilling of deep micro-holes in hard rocks. Cyclic bending of the coiled tubing past the yield strength point of the material leads to progressive weakening of the tube, which accordingly leads to rapid reduction of the tube service life [1]. Hence fatigue is an important parameter that needs to be considered in material selection for coiled tube and rig design. A bending machine was designed and manufactured to evaluate the fatigue bending strength of conventional HSLA steel tubes. The machine is capable of measuring and recording the bending/flattening resistant forces of the tubes along with the number of bend/flatten events. It can also measure the strain applied on the tube if needed. In this study, several HSLA steel grades and thicknesses of coiled tubes were tested for fatigue bending strength. Fatigued and non-fatigued tubes had their mechanical property alteration tested using tensile test methods.
This paper presents the fatigue bending machine. The machine is designed to test most material types of coiled tubes. The paper also reports results of the cyclic bending experiments that were performed on selected grades and sizes of conventional HSLA steel coiled tubes. The paper complements and enhances the understanding of the performance of conventional coiled tube material under fatigue bending conditions.
Scale Tests of the GICON®-TLP for Wind Turbines
Authors: Adam F. , Myland T. , Dahlhaus F. , Großmann J. 
Published: September 2014

The paper will present the preliminary design of the so called GICON® - Tension Leg Platform (TLP) as an innovative foundation concept for floating offshore wind turbines.
Preliminary results from model basin tests are also shared. This includes the currently ongoing research of comparing calculated and experimental data obtained through extensive wind and wave tank experiments with a scale model of an offshore wind turbine at the Maritime Research Institute Netherlands (MARIN) in June 2013. These tests have provided insights regarding the dynamic characteristics of the GICON®-TLP by analyzing the system’s response to different load cases.
The experiments included wind and wave loads, which represent three different sea states, each with three different directions of inflow. The chosen load cases correspond to the proposed location in the German Baltic Sea where the full scale prototype will be erected.
Reducing Roll Motion by Passive Free Surface Tanks
Authors: Nielsen Christian S. , Nielsen Ulrik D. 
Published: September 2014

Roll stabilisation of motorised vessels plays an important part in reducing passenger discomfort and increasing safety and cargo capacity. Passive free surface tanks are considered a low-cost stabilising method, which is efficient at all speeds without increasing hull resistance.
In this study, a mathematical model for evaluating the performance of a passive free surface tank is established. This is done by coupling a roll model to a fluid flow model. As a numerical example, the seakeeping abilities of a container vessel are evaluated. The necessary methods for performing the simulation are presented and the design of a free surface tank is explained.
The effects of the passive free surface tank are evaluated and a significant damping effect is observed, particularly in cases with resonant roll.
Theoretical Investigation on Ice Resistance Prediction Methods for Ships in Level Ice
Authors: Myland Daniela , Ehlers Sören 
Published: September 2014

The assessment of the ship performance in ice covered waters has become more and more important in view of the increased interest in Arctic field logistics and transportation. The performance of ice-going or ice breaking ships is usually defined by their ability to proceed in uniform level ice, where good performance means low ice resistance, high propulsion efficiency and continuous ice breaking. In order to assess the ice breaking performance in an early design stage, model tests may be executed or several theoretical methods may be applied to predict the ice resistance may be applied. Due to the physical nature of model tests, all processes, i.e. forces contributing to ice resistance are considered. Thus, the execution of model tests is still the most reliable method to determine the ice resistance. But with regard to the high costs of model tests there is continued demand to gain knowledge on the reliability of theoretical prediction methods. The applicability of the method of choice depends on the underlying assumptions of the method itself and thus the method’s capability to predict and consider physical phenomena of interest.
In this paper model tests are used to evaluate the influence of hull shape parameters and ice conditions on the breaking process, i.e. the ice resistance and the ship performance. Based on the knowledge gained a systematic comparison of existing, representative ice resistance prediction methods is carried out. The methods considered are state-of-the-art techniques which the original publications introduced with sufficient information to allow for their use in this comparison. It focuses on the suitability of the existing methods as engineering tools for the prediction of different components, as well as the total ice resistance itself. The incorporation of the ice resistance contributions in the different prediction methods is presented and differences are identified. On this basis an assessment of the assumptions and simplifications of these different numerical methods is outlined.
New Insights Into the Flooding Sequence of the Costa Concordia Accident
Authors: Dankowski Hendrik , Russell Philipp , Krüger Stefan 
Published: September 2014

The tragic accident of the Costa Concordia in January 2012 was one of the most severe large passenger ship accident in Europe in recent times followed by a tremendous public interest. We present the results of an in-depth technical investigation of the flooding sequence which lead to the heeling and grounding of the ship.
A fast and explicit numerical flooding simulation method has been developed in the last years to better understand accidents like this one caused by complex and large scale flooding events. The flooding simulation is validated with the help of results from model tests and has been successfully applied to the investigation of several other severe ship accidents. It is based on a quasi-static approach in the time domain which evaluates the hydrostatic equilibrium at each time step. The water fluxes through the openings are computed by a hydraulic model based on the Bernoulli equation. Large and partly flooded openings are taken into account as well as conditional openings like the opening, closing and breaking of doors. The fluxes are integrated in the time domain by a predictor-corrector integration scheme to obtain the water volumes in each compartment involved in the flooding sequence.
Due to the fact that the accident happened in calm water at moderate wind speeds close to the shore of the island Giglio this quasi-static numerical flooding simulation can be applied. The results of the technical investigation of the Costa Concordia accident obtained with the help of the developed method are presented. These results match well with the heel and trim motions observed during the accident and the chain of events which lead to the final position of the vessel on the rocks in front of the island Giglio.
The explicit and direct approach of the method leads to a fast computational run-time of the numerical method. This allows to study several possible accident scenarios within a short period to investigate for example the influence of the opening and closing of watertight doors and to identify a most likely flooding scenario which lead to this tragic accident.
Frequency Versus Time Domain Fatigue Analysis of a Semi-Submersible Wind Turbine Tower
Authors: Kvittem Marit I. , Moan Torgeir 
Published: September 2014

The current paper addresses a study of a semi-submersible wind turbine, where tower base bending moments and short term tower fatigue damage was estimated by a frequency domain method assuming two-dimensional platform motions. Both a rigid structure assumption and a generalised degree of freedom model for including the first flexible mode of the turbine were investigated. First, response wind- and wave loads were considered separately, then superposition was used to find the response to combined wind and wave loading. The bending moments and fatigue damage obtained by these methods were compared to results from a fully coupled, non-linear time domain analyses.
In this study a three column, catenary moored semi-submersible with the NREL 5MW turbine mounted on one of the columns was modelled. The time domain simulation tool used was Simo-Riflex-AeroDyn from Marintek and CeSOS.
The frequency domain method accounting for a flexible turbine gave a good representation of the tower base bending moment histories for the moderate sea states in these analyses, also for the combined wind and wave analyses. The frequency domain fatigue damage predictions were underestimated by 0–60%, most likely due to the exponential relationship between damage and stress amplitude.
Wave-in-Deck Load on a Jacket Platform, CFD Calculations Compared With Experiments
Authors: Iwanowski Bogdan , Vestbøstad Tone , Lefranc Marc 
Published: September 2014

The paper presents an industrial application of CFD for calculation of Wave-In-Deck load due to an extreme wave.
Particular attention is given to flow kinematics initialization that is necessary to start up a CFD simulation. The applied CFD code, ComFLOW, is a Navier-Stokes equation solver with an improved Volume of Fluid (iVOF) method employed to displace and re-construct fluids free surface.
For incoming waves high enough for a negative air-gap and therefore with Wave-In-Deck loads, a jacket platform was tested in model basin, for both regular and irregular wave cases. One of goals of these model tests was verification of CFD codes. The experimental and computational models of the structure are exactly the same. In the paper, the measured Wave-In-Deck forces are compared with CFD results.
The First Standard for Certification of HATT: The Application of Risk Based Approach
Authors: Bittencourt Claudio , Zarraonandia Gaizka , Vinogradov Alexey , Cocho Mathieu 
Published: September 2014

As part of the ReDAPT, a project commissioned and co-funded by the ETI (Energy Technologies Institute), the first standard for certification of horizontal axis tidal turbine (HATT) has been commissioned to DNV GL in order to accelerate the development of the tidal technology and its commercialization. Although the development of the standard is limited to one turbine concept and unlike the wind turbines, the possible variations of configurations and the limited track record of the technology provided great challenges to define requirements and parameters to be considered in all aspects of the turbine.
A risk based approach has been used on the different HATT configurations, addressing all the systems, subsystems and main components. The process, as described in the DNV OSS-312 – Certification of Tidal and Wave Energy Converters, addressing technology assessment and FMEA leading to a certification plan and definition of standards from Oil & Gas / Wind to be applied, was implemented in a level of detail sufficient to define the failure modes and associated risks that were the basis for definition of design, construction, commissioning and in-service life requirements.
The work on failure modes and risks as well as data and definitions necessary for an effective risk based process were carried out with the support and assistance of ALSTOM during the ReDAPT project and the experience accumulated by DNV GL in the verification / certification projects carried out so far.
Although every standard has a risk based background (even if based on field experience for many years), this standard has a direct connection between the identified risks and requirements. As the risks can vary for a specific configuration of HATT, technology matures and data is harnessed with the passing of the time, the approach used will allow for a faster and consistent adaptation of the standard now and in the future.
This paper, describes the process in detail, presents the structure used for the risk assessment process, its conclusions and highlights the connection between the findings and the content of the standard.
Fatigue Performance of Grade R4 and R5 Mooring Chains in Seawater
Authors: Fernández Jonathan , Storesund Walther , Navas Jesús 
Published: September 2014

With more than 50.000 tons in service to date, the Oil&Gas Industry has the need to understand the tension fatigue performance of grade R5 chains in straight tension, and corroborate the validity of the existing design methods.
The chain fatigue design curves in API and DNV are based on fatigue tests obtained in the nineties and early two thousands. However the tests were performed on lower grades such as ORQ, R3 and R4, and small chains, 76 mm diameter being the largest studless chain tested.
The industry has moved towards the use of large studless chains, especially in permanent units, where chain diameters above 150 mm are not unusual.
This paper gathers information from a full scale fatigue test program on grade R4 and R5 studless chains, performed in seawater and with diameters between 70 mm and 171 mm. The chains being tested are actual production chains supplied for different drilling units and large permanently moored production floating units.
The paper analyses the data and determines tension-tension fatigue curves based on API and DNV methods for computation of cumulative fatigue damage, regardless of other damaging mechanisms. Improved fatigue capacity is obtained with respect to the above recommended design methods.
The Tension Leg Semisubmersible (TLS): The Hybrid TLP-Semisubmersible Floater With the Spar Response
Authors: Mansour Alaa M. , Wu Chunfa , Kumar Dhiraj , Zuccolo Ricardo 
Published: September 2014

The Tension Leg Semisubmersible (TLS) floater is the second generation of the Free-Hanging Solid Ballast Semisubmersible (FHSB Semi) design. The FHSB Semi is the state-of-the-art design that maintains the advantages of the conventional Semisubmersibles and provides the motions of Spars. The FHSB Semi design is a conventional semisubmersible with an added feature of a Free-Hanging Solid Ballast tank (SBT) located deep below the hull keel level and connected through four groups of chains (on its four corners) to the semisubmersible hull. During the pre-service conditions, the chains are used to retract the SBT and maintain it at a close proximity to the hull keel to facilitate the transportation and installation operations. Once the semisubmersible is moored in-place, the chain system is operated to lower the SBT to its desired elevation below the hull keel and maintain it permanently connected to the semisubmersible hull during the in-service condition. The SBT provides substantial in-water weight and added mass that significantly reduce the platform response and maintains the chains in tension.
In this paper, detailed description of the Tension Leg Semisubmersible (TLS) design as the second generation of the FHSB Semi is presented. The paper also includes discussions on the proposed project execution plan for the TLS covering the fabrication, transportation and installation as well as the added risks and risk mitigations associated with the new semisubmersible design and execution.
A case study is introduced where a TLS is used as a dry tree host for a field located at 6,000 ft of water in the central Gulf of Mexico (GoM) harsh environment.