bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Investigations of Offshore Triceratops Under Regular Waves
Authors: Chandrasekaran Srinivasan , Sundaravadivelu R. , Pannerselvam R. , Madhuri S. , Varthini D. Shyamala
Published: November 2011

For the development of marginal deep water oil fields many new platform concepts and design are emerging. Offshore triceratops is a relatively new concept for ultra deep water oil exploration. Triceratops has desirable characteristics of both TLP and Spar. It consists of deck structure supported on three buoyant leg structures (BLS) connected through ball joints. These joints make them a stable and heave restrained system; they do not pitch and roll but have limited surge and sway. The three BLS structures are connected to sea floor by tethering system. The present study discusses detailed experimental investigations carried out to analyze the structural response on the 1:150 scaled model of triceratops under regular waves. Influence of ball joints and tether tension variation on deck response is studied. Based on the experimental studies conducted, it is seen that deck response of Triceratops is relatively lower than BLS; deck remains horizontal for the encountered wave loads.
Maximum Crest Heights Under a Model TLP Deck
Authors: Forristall George Z.
Published: November 2011

Theory and simulations have shown that the maximum crest height in an area can be substantially greater than the single point maximum. Theoretical results have been tested and confirmed using data from a 10 by 10 array of wave probes in the Marin Offshore Basin. Estimation of the maximum crest height under a TLP’s deck is more complicated than it is in unobstructed waters. A TLP’s large columns diffract and radiate incident waves. Fortunately, the short term statistics of the diffracted waves have the same form as the short term statistics of the incident waves. The maximum crests under the TLP are estimated by using diffraction theory to find the wave spectra at each point. Then, linear simulations are used to find time series at each point. Finally, the linear maxima are multiplied by the ratio between the theoretical linear and second order crest heights. Comparisons with measurements from wave probes placed under a TLP model in the Marin Offshore Basin support the accuracy of this process. These results mean that the maximum crest heights in the area under a deck must be considered in air gap calculations.
Offshore Reliability Approach for Floating Renewable Energy Devices
Authors: Johanning Lars , Thies Philipp R. , Parish David , Smith George H.
Published: November 2011

This paper describes the test facilities developed within the Peninsular Research institution for Marine Renewable Energy (PRIMaRE) group and discusses the approach of the group to mitigate risk for marine renewable energy installations. The main consideration is given to the reliability assessment of components within mooring configurations and towards power umbilical for typical renewable energy sites. Load and response data from sea trial will be used to highlight the importance of these research activities, and a Dynamic Marine Component Test rig (DMaC) is introduced that allows four degree of freedom fatigue or destructive tests. Furthermore it is discussed how this facilities could also aid in the reliability assessment of wider offshore applications.
An Experimental Study on the Waterway Rescue System for Natural Disasters in the Tokyo Metropolis
Authors: Yu Chiu Hsien , Oikawa Tomoe , Miyazaki Wataru , Kondo Takeo , Yamamoto Kazukiyo , Egami Kazuya
Published: November 2011

When the Great Hanshin Awaji Earthquake struck Japan in 1995, water transportation effectively supported rescue operations. Subsequently, Tokyo metropolitan government created a plan for a series of disaster relief piers in preparation for the Tokyo Metropolitan Epicentral Earthquake. In this study, we carried out field surveys for nine disaster relief piers which were established by the Japanese government, the Tokyo metropolitan government, and the wards in Tokyo, in order to find out issues of disaster relief piers for wheelchair users in case of a disaster. In the surveys, we checked the actual conditions of barrier-free implementation of the disaster relief piers, and analyzed the accessibility from the shelters to the disaster relief piers in terms of the shortest distance and travel time. As a result, we elucidated various mobility barriers for wheelchair users when they evacuate to the disaster relief piers.
Turkstra Profiles of North Sea Currents: Wider Than You’d Think
Authors: Winterstein Steven R. , Haver Sverre , Jha Alok K. , Kvingedal Borge , Nygaard Einar
Published: November 2011

To design marine structures in deep water, currents must be modelled accurately as a function of depth. These models often take the form of T-year profiles, which assume the T-year extreme current speed occurs simultaneously at each depth. To better reflect the spatial correlation in the current speeds versus depth, we have recently introduced Turkstra current profiles. These assign the T-year speed at one depth, and “associated” speeds expected to occur simultaneously at other depths. Two essentially decoupled steps are required: (1) marginal analysis to estimate T-year extremes, and (2) some type of regression to find associated values. The result is a set of current profiles, each of which coincides with the T-year profile at a single depth and is reduced elsewhere. Our previous work with Turkstra profiles suggested that, when applied in an unbiased fashion, they could produce unconservative estimates of extreme loads. This is in direct contrast to the findings of Statoil, whose similar (“CCA”) current profiles have generally been found to yield conservative load estimates. This paper addresses this contradiction. In the process, we find considerable differences can arise in precisely how one performs steps 1 and 2 above. The net finding is to favor methods that properly emphasize the upper tails of the data—e.g., using peak-over-threshold (“POT”) data, and regression based on class means—rather than standard analyses that weigh all data equally. By applying such tail-sensitive methods to our dataset, we find the unconservative trend in Turkstra profiles to essentially vanish. For our data, these tail-fit results yield profiles with both larger marginal extremes, and broader profiles surrounding these extremes—hence the title of this paper.
Conceptual Design of a Submersible Remotely Operated Swimming Dredger (SROSD)
Authors: Sarkar Mridul K. , Bose Neil , Chai Shuhong , Dowling Kim
Published: November 2011

Increasing use of deep-water dredging and mining vehicles has been anticipated for resource collection, engineering construction and environmental protection. Existing deep-dredging or mining equipment can be classified as i) diver-assisted dredging tools, ii) surface-floating dredgers with deep-dredging capability and iii) submersible dredgers. Diver assisted dredging tools have limited capacity and involve human risk. Surface floating dredgers can work to a specific dredging depth controlled by their ladder length, but modification is limited by their large size and significant cost. Submersible dredgers are deployed for sub-sea operations and are the focus of this research. Submersible crawlers and walkers work in a submerged terrain-contact condition and depend on their apparent weight and ground reactions to counteract the excavation forces. Crawlers are inefficient in negotiating difficult sub-sea terrain and walking submersibles are slow moving over long-distances. Considering the constraints of dredging depth, negotiation of uneven terrain, slow motion, interchange ability of excavation or transport sub-system components and station keeping during operation, a new type of submersible dredger or miner was conceived. In working mode, it imitates a walking motion by spuds that are also used for station keeping during dredging. For longdistance travel, the vehicle can swim by means of vector thrusters. The vector thrusters also help in position-keeping and motion-control during swimming. To offset higher forces generated during excavation of hard materials, spuds, variable buoyancy tanks and control planes are included as secondary station-keeping devices. The paper describes the general arrangement and the distinguished sub-systems of the conceptualised vehicle. Special attention was given to working and swimming locomotion and the methods of station keeping during operation. Investigations about the station-keeping, propulsion and controlling conditions of the vehicle are in progress. Experiments to measure the cutting forces from the cutter design are described. It is expected that the new design will significantly contribute to the evolution of existing deep-dredging equipment with improved efficiency, increased mobility and location control while minimising larger environmental disturbances.
Suction Pile Foundations: Experience in the Mediterranean Offshore and Installation Feedback
Authors: Bughi Sabrina , Parker Eric
Published: November 2011

Suction piles are widely used in deepwater engineering both for anchoring and as foundation systems. In the first case the piles serve as anchor points for mooring systems in alternative to more standard drag anchors or piles. More recently, however, they have been used as structure foundations. In this role suction piles are a competitive alternative to the more traditional solutions of driven piles or mudmats, for platform jackets, subsea systems and subsea equipment protection structures. This solution provides cost savings in fabrication and required installation equipment. Furthermore, the foundations are relatively easy and rapid to install and can be positioned with high precision by controlled and simple marine operations, and they can be removed for reuse. This paper describes the use of steel suction piles for deepwater subsea Manifolds, Tie-in Spool Bases and Subsea Control Distribution Assemblies, in the West Delta Deep Marine (WDDM) and Rosetta concessions offshore Egypt. Most of the structures were supported by a single suction pile foundation; pile diameters ranged from 4 m to 8 m and penetrations from 8 m to 12 m. One of the larger units was supported by a “quad” foundation frame with four suction piles. Soils in the area are very soft, normally consolidated clays typical of deepwater conditions. Design is complicated by seismicity of the area, which required the foundations to resist significant horizontal dynamic loads in addition to the normal vertical operating loads. The solution adopted utilized an internal top plate in contact with the soil allowing full development of base bearing capacity. As the pile skin friction in these soils is very low, the increased end bearing leads to significant savings on foundation weight and cost. The paper discusses the main aspects of foundation design, covering the installation process with expected self weight penetration and the required suction to achieve the target design penetration, the retrieval operation for repositioning in case the final inclination is out of tolerance, the assessment of the bearing capacity and the stability under the combined vertical, horizontal and overturning loads during operation and earthquake conditions. Seismic design was based on a nonlinear dynamic analysis. In some cases the seismic loads were comparable to the ultimate foundation capacity and the final acceptance criteria utilized a Performance Based Design philosophy. In this approach the foundation is considered acceptable if the deformation experienced by the structure, during and after the seismic event, does not jeopardize structural integrity.
On the Propagation Buckling and Effects in Ultra-Long Deep Subsea Pipelines
Authors: Khalilpasha Hossein , Albermani Faris
Published: November 2011

This paper considers buckling propagation in ultra-long deep subsea pipelines. Experimental investigation of buckle propagation in ultra-deep pipelines was conducted to verify the analytical solutions proposed by the authors in a previous paper [1]. A series of experiments were designed and conducted to calibrate the equations and verify the analytical and numerical results. The tests include tensile coupon tests, ring squash tests and buckle propagation tests on intact and dented Aluminum pipes with three different D/t ratios. The results are in good agreement with the proposed analytical solution.
Shipboard Measurement of Ocean Waves
Authors: Fu Thomas C. , Fullerton Anne M. , Hackett Erin E. , Merrill Craig
Published: November 2011

Over the past several years a number of techniques have been utilized for the measurement of ocean waves from shipboard platforms. These systems have ranged from commercial off the shelf (COTS) navigation radar and Light Detection and Ranging (LIDAR) systems to specially developed in-house instrumentation systems. Most of these systems have been utilized to measure the directional wave spectra around the ship. More recently, the Naval Surface Warfare Center, Carderock Division (NSWCCD) and others have begun to utilize these techniques for shipboard measurement of individual ship generated waves as well as open ocean waves. NSWCCD has used a number of these methods on various Office of Naval Research (ONR) and Naval Sea Systems (NAVSEA) sponsored field tests. These field tests were performed on a variety of naval platforms over a range of sizes, including some fixed platforms, for various sea states. While each of these tests has had individual measurement goals and objectives, the series of tests has also provided an environment for testing and developing new instrumentation and exploring their capabilities. As a result of these efforts, instrumentation has grown in sophistication from qualitative video-based observations of the wave field around an underway vessel to laser and radar based imaging and ranging measurements of free surface dynamics. This work has led to higher fidelity data, as well as data that were previously unobtainable. In this paper we provide an overview of these systems and techniques and summarize the basic capabilities of each method by providing measurement examples/applications. These systems include a shipboard array of ultrasonic distance sensors for measuring directional wave spectra, a COTS wave radar system, and a COTS scanning LIDAR system. While not intending to be exhaustive, this paper seeks to highlight the insights gained from the recent applications of these techniques, as well as the difficulties and issues associated with shipboard measurements such as ship motion and logistical constraints.
Industry Developed Guidelines and Standards for Ageing and Life Extension
Authors: Selnes Per Otto , Ersdal Gerhard
Published: November 2011

A large number of the Norwegian gas and oil production facilities have exceeded their initial design life but the respective fields are still producing substantial levels of hydrocarbons. In order to ensure technical and operational integrity of these ageing facilities, the Norwegian oil industry Association (OLF) has initiated a project to establish the necessary standards and guidelines for assessing and ensuring safe life extensions. This paper presents this project and the headlines of these standards and guidelines.
Environmental Research for Assessing the Impacts of Mining Seafloor Massive Sulfides in Japan
Authors: Toyohara Tetsuhiko , Okamoto Nobuyuki , Kawai Takahiro , Kodama Takayoshi , Shibasaki Hiroshi
Published: November 2011

In Japan, the Ministry of Economy, Trade and Industry (METI) commenced a research and development (R&D) project on seafloor massive sulfide (SMS) deposits in Japan’s exclusive economic zone (EEZ) in the 2008 fiscal year. The project defines the plan for the commercialization of SMS within 10 years. Japan Oil, Gas and Metals National Corporation (JOGMEC) conducted the research under contract to METI. SMS deposits are widely distributed in the sea area surrounding Japan and are expected to become domestic metal resources. Since the SMS fields include hydrothermal ecosystems, which often host dense endemic animal communities, an adequate environmental impact assessment (EIA) and a conservation strategy to protect biodiversity are required for sustainable development. We outline an environmental framework that is intended to contribute to a global standard for assessing the environmental impacts of SMS exploration and mining.
35 Year Old Jackets Removed as a Single Piece
Authors: van Hoof Jochum C. G. , de Bruin Ruben
Published: November 2011

Heerema Marine Contractors (HMC) have removed and will be removing various platforms from the North Sea. For these projects Heerema has developed an unconventional method to remove and transport jackets: Jackets are lifted as one single piece and transported to the recycling yard whilst being suspended from both cranes of the Heavy Lift Vessel (HLV) Thialf. Two purpose built structures at the stern restrain the jackets from horizontal motions during transport. In summer 2010 three eight-legged jackets were removed and transported using this method (see Figure 1). The jackets weighed approximately 5,000 metric tonnes each and stood in 70–80m of water. The jacket removal resulted in load cases that were never considered during jacket design. Jacket strength appeared very marginal when cutting the jacket into several sections, but by lifting the jacket as one single section, all members remained connected and ensured a stable structure. Other benefits were reduction of the offshore project duration, the subsea cutting scope and the required vessel spread. Risk on weather downtime was reduced and safety improved by preventing back loading operations in an offshore environment. The transport distance with the jacket suspended from both Thialf cranes ranged from 200–300 nautical miles (1 1/2–2 1/2 days sailing). The final cuts and the jacket lifting required relatively low sea states. The wave climate for transport was determined with the assumption of a preceding weather sensitive operation, which is different to a transport that assumes a start at a random time. Model tests for these design sea states have been performed to accurately assess the Thialf dynamic behavior at its shallow transit draught. Additional analyses were performed to confirm the vessel-jacket dynamic interaction. During transport the so called ‘restraints’ gripped around the jacket corner legs, restraining the structure horizontally and preventing side loads on the cranes. During the three transports, motions have been measured and dynamic behavior corresponded well with the analyses. Removing and transporting these jackets as a single piece was a unique operation. The method worked well and resulted in a predictable, safe and time efficient jacket removal. This paper will address the removal method, including structural aspects, model tests and full scale verification.
Refining an Eddy Viscosity Model for Two-Dimensional Breaking Waves in Deep Water: Experiments
Authors: Tian Zhigang , Choi Wooyoung , Perlin Marc
Published: November 2011

This paper presents an experimental study of breaking waves in deep water, as part of the effort to further develop an eddy viscosity model for wave breaking, originally proposed by Tian, Perlin & Choi (2010, J. Fluid Mech. 655, 217–257). In the previous work, the wave breaking time, location, and breaking strength were required a priori for numerical simulations. It is our intention to make further refinement so that the improved eddy viscosity model automatically predicts wave breaking onset, determines local wave parameters at breaking onset, and forecasts post-breaking time and length scales to estimate the magnitude of the eddy viscosity. As the first part of the further development, we conducted wave breaking experiments, in which breaking wave groups are generated using both wave energy focusing and modulational instability. Surface elevations as a function of time are measured and surface profiles as a function of space during active breaking events are captured. Local wave parameters at wave breaking onset (pre-breaking parameters) are defined and determined, as well as the post-breaking time and length scales. Correlations among the parameters at breaking onset and the post-breaking scales are identified. Similarities and differences of the two types of breaking wave groups are provided and discussed.
Numerical Analysis of a Novel Method for Subsea Equipment Installation
Authors: Rateiro Felipe , Fucatu Carlos H. , Neves Cassiano R. , dos Santos Melquisedec F. , Tannuri Eduardo A.
Published: November 2011

This paper and the companion paper OMAE2010-49946 (de Mello et al., 2011) present the experimental and numerical results of the analyses of a novel method for subsea equipment installation. The conventional procedure, which is usually used, may lead to dynamic amplifications, depending on the launching cable stiffness and length. In the proposed method the equipment is lowered using two tug boats in a Y configuration. Trough the control of their relative position and also of the cable length it is possible to diminish the tension amplification.
Efficient System Reliability Analysis by Finite Element Structural Models
Authors: Gaspar Bruno , Naess Arvid , Leira Bernt J. , Guedes Soares C.
Published: November 2011

In principle, the reliability of complex structural systems can be accurately predicted through Monte Carlo simulation. This method has several attractive features for structural system reliability, the most important being that the system failure criterion is usually relatively easy to check almost irrespective of the complexity of the system. However, the computational cost involved in the simulation may be prohibitive for highly reliable structural systems. In this study a new Monte Carlo based method recently proposed for system reliability estimation that aims at reducing the computational cost is applied. It has been shown that the method provides good estimates for the system failure probability with reduced computational cost. By a numerical example the usefulness and efficiency of the method to estimate the reliability of a system represented by a nonlinear finite element structural model is demonstrated. To reduce the computational cost involved in the nonlinear finite element analysis the method is combined with a response surface model.
Engineering Critical Assessment of Embedded Flaws in a Pipeline Using a Probabilistic Approach: A Case Study
Authors: Zhou Daowu , Mirzaee-Sisan Ali
Published: November 2011

A probabilistic engineering critical assessment of embedded flaws in a pipeline was carried out as a case study using the limit state function based on both finite element analysis and the failure assessment diagram. The response surface model was used in determining the finite element analysis based limit state function in order to reduce the number of finite element analysis runs. The first order reliability method and second order reliability method were used to determine the probability of failure. This research work highlights the advantage of using specific limit state function for engineering critical assessment of embedded flaws.
Uniform Flow Past a Rotary Oscillating Circular Cylinder
Authors: Du Lue Derek , Dalton Charles
Published: November 2011

In this paper, we study uniform flow past a rotary oscillating circular cylinder computationally. The objective is to determine the effect the oscillating rotation has on the lift and drag forces acting on the cylinder, on the wake structure, and on vortex shedding. A combination of finite-difference and spectral methods is used to calculate the three-dimensional incompressible unsteady Navier-Stokes equations in primitive variable form in nonorthogonal curvilinear coordinates. Wake turbulence is modeled by an LES technique. The Reynolds number considered is Re = 1.5×104, which is the same as that in the experimental study of Tokumaru & Dimotakis (1991), who suggested this technique as a means of reducing drag. We fix the forcing amplitude at the moderate value of Ω = 2 and vary the forcing frequency in a wide range to study its effect on the flow. The resonance phenomenon and drag reduction effect are carefully examined. The wake structure and vortex shedding process is visualized by means of computational streaklines. These results have a practical application in offshore engineering.
Integrated Analysis of Mooring and Riser Systems for FPSO’s in Harsh Shallow Water Environments
Authors: Martens M. , Whelan J. R. , Drobyshevski Y.
Published: November 2011

Shallow water mooring and riser systems for permanently turret moored FPSOs present significant design challenges. Many FPSOs, in particular in the South-East Asia region, are required to remain on-station in 100-year return period tropical revolving storm (typhoon) conditions. Extreme sea states combined with the restricted height of the water column generate large mooring loads and make it difficult to accommodate conventional riser configurations. Metocean conditions in such areas can be highly directional. This directionality can be exploited by undertaking an integrated mooring and riser design analysis. The critical interface between the mooring and riser systems is the turret offset and the associated turret heave. The conventional approach is to identify a single offset envelope for each design case, comprising the mooring system (intact or damaged) and FPSO condition (loaded or ballasted), which is then used in riser design. This paper presents a more developed approach, the integrated approach, which is based on conducting the mooring and riser analyses simultaneously for a common set of design cases. To exploit the directionality of the metocean conditions, an offset envelope for each governing metocean condition is calculated from time domain mooring simulations, followed by a parameterisation scheme. As a result, multiple turret offsets and associated metocean conditions and FPSO headings are identified which form a family of offsets for each compass octant of the environment. The integrated approach is applied to an example FPSO with an external turret supporting seven risers arranged in double wave tethered configuration. The drivers and advantages for selecting a particular riser configuration are discussed. It is shown how application of an integrated analysis approach leads to less conservative combinations for use in the riser design, and enables the development of a feasible riser system. An optimal mooring pattern, both leg make-up and orientation for riser layout, is also developed.
Wellhead Fatigue Analysis Method
Authors: Reina˚s Lorents , Ho̸rte Torfinn , Sæther Morten , Gryto̸yr Guttorm
Published: November 2011

Re-completion and re-drilling of existing wells and introduction of new large drilling rig systems are elements that have led to renewed focus on the fatigue capacity for existing and new subsea wells. Due to lack of applicable codes and standards for such fatigue calculations, a unified analysis methodology has been developed and described in a Wellhead Fatigue Analysis Method Statement (MS). The intention of this work is to reflect the best practice in the industry and to provide an important contribution to well integrity management. The analysis methodology is limited to fatigue damage from dynamic riser loads present during subsea drilling and work over operations. The analysis procedure may be divided into three parts. i) A local response analysis that includes a detailed finite element model from wellhead datum and below. Interaction between the structural well components and soil structure interaction is properly accounted for. The main result from this analysis is the load-to-stress curve that describes the relationship between the riser loads at the wellhead datum and the stress at the fatigue hot spots. The analysis also provides the lower boundary conditions of the global load analysis model. ii) A global load analysis where the floating mobile drilling unit (MODU) motions and wave loads on the riser are taken into account. The results are time series or load histograms of the loads at wellhead datum, with focus on the bending moment, in all relevant environmental sea states. iii) Fatigue damage assessment, where a mapping of the loads with the relevant load to stress curve is carried out together with subsequent fatigue damage calculation. Appropriate S-N curve is applied together with wave scatter diagrams for the relevant operations and durations. The final result is the accumulated fatigue damage. With a unified analysis methodology in place particular attention is placed on a structured and specified analysis input and output. Results are suggested presented as a function of time and also as a function of key analysis input parameters that are associated with uncertainty. These are prerequisites from a well integrity management perspective in ensuring analysis results that are comparable. This paper presents the essence of the Wellhead Fatigue Analysis Method that was developed in cooperation between Statoil and DNV. Currently this analysis methodology is under extension and revision in the joint industry project (JIP) “Structural Well Integrity During Well Operations”. 11 operators participate in this JIP which also has structured cooperation with equipment suppliers, drilling companies and analysis houses. The aim is to form a wellhead analysis recommended practice document.
Structural Design of a Horizontal-Axis Tidal Current Turbine Composite Blade
Authors: Bir Gunjit S. , Lawson Michael J. , Li Ye
Published: November 2011

This paper describes the structural design of a tidal turbine composite blade. The structural design is preceded by two steps: hydrodynamic design and determination of extreme loads. The hydrodynamic design provides the chord and twist distributions along the blade length that result in optimal performance of the tidal turbine over its lifetime. The extreme loads, i.e. the extreme flap and edgewise loads that the blade would likely encounter over its lifetime, are associated with extreme tidal flow conditions and are obtained using a computational fluid dynamics (CFD) software. Given the blade external shape and the extreme loads, we use a laminate-theory-based structural design to determine the optimal layout of composite laminas such that the ultimate-strength and buckling-resistance criteria are satisfied at all points in the blade. The structural design approach allows for arbitrary specification of the chord, twist, and airfoil geometry along the blade and an arbitrary number of shear webs. In addition, certain fabrication criteria are imposed, for example, each composite laminate must be an integral multiple of its constituent ply thickness. In the present effort, the structural design uses only static extreme loads; dynamic-loads-based fatigue design will be addressed in the future. Following the blade design, we compute the distributed structural properties, i.e. flap stiffness, edgewise stiffness, torsion stiffness, mass, moments of inertia, elastic-axis offset, and center-of-mass offset along the blade. Such properties are required by hydro-elastic codes to model the tidal current turbine and to perform modal, stability, loads, and response analyses.
Safety Assessment of Cargo Containment Systems in LNG Carriers Under the Impact of Iceberg-Ship Collision
Authors: Kim Jae-Hyun , Oh Hoon-Kyu , Kim Doe-Hyun
Published: November 2011

Arctic and sub-arctic regions of Russia are home to some of the large gas reservoirs, attracting numerous energy development projects. A ship-borne transportation system connecting these potential gas fields to gas terminals in Gulf of Mexico will likely be established. In this case, the integrity and safety of LNG cargo containment systems under impact of the iceberg-ship collision should be carefully considered at conceptual and detailed design phase. The collision impact by an undetected iceberg should be considered to be an accidental load. Thereby, plastic deformations of the hull structure may be accepted provided the LNG will not leak out. Till now, view points of the safety evaluation have been limited to structural hull deformations by the collision. They have not examined effects of vibratory acceleration induced by the impact on the structure of LNG containment systems, even though it seems rather rational in case of substructure such as LNG containment systems in independent type or membrane type LNG carriers. In this paper, the iceberg-ship collision scenario is established based on International Ice Patrol’s reports. The comparative safety assessment of cargo containment systems for independent type (spherical and SPB) and membrane type (Mark-III and NO96) LNG carriers is performed through a computational simulation and the related experimental research works.
Random Collocation Method (RCM)
Authors: Isshiki Hiroshi
Published: November 2011

Recently, young people do not show much interest on theory, and a lack of communication is occurring between the older and younger generations. This tells us that a much simpler numerical procedure directly related to the governing equations is strongly required and the effort answering the requirement should be continued. If there is a numerical procedure that is friendlier with theory, the distance between theory and calculation would be decreased much, and the interaction among people in both fields would become more active. When the geometry of the domain is simple, the traditional analytical method using function expansion is very convenient in many numerical problems. In many problems, it has given very useful solutions for various problems. However, its effectiveness is usually limited to simple geometries of the domain. In the past, a fusion of the analytical approach and computational one has not been pursued sufficiently. If it becomes possible, it may give a different paradigm for obtaining the numerical solution. In the present paper, a very simple and innovative idea named Random Collocation Method (RCM) is discussed on how to overcome the weak point of the traditional method by combining it with computational method. It is the purpose of the present paper to develop the simplest numerical method and to make the distance between the theory and numerical method as small as possible.
Pipeline Embedment Prediction Using As-Laid Data
Authors: Oliphant John , Yun Gi Jae
Published: November 2011

Pipe embedment defines the initial condition of the pipeline following installation and is fundamental to the calculation of both axial and lateral resistance of pipelines. However, the initial embedment depth of a pipeline is notoriously difficult to predict. The influence of cyclic loading during pipe-lay is known to significantly increase embedment. However, there is no known empirical work or data from which to model or predict the additional embedment associated with the dynamics of the pipelay operation. As-laid data from pipelines must be viewed as the best guide. Field survey embedment data are presented for a rigid pipeline installed in deep and shallow water clay sediments. These data are used to re-evaluate the models used for predicting the initial pipe embedment. Recommendations are given on the dynamic embedment factor required to account for the dynamic effects at the touchdown region during installation. The results demonstrate that the initial pipeline embedment is much more dependent on the dynamic installation loads and less on the stress concentration at touchdown.
ISO 19902 Tubular Members Including Damaged and Grouted Members
Authors: Frieze Paul A.
Published: November 2011

The background and basis of the ISO 19902 tubular member strength formulations is described. Many of the simpler provisions were initially based on the then existing API RP 2A LRFD formulations whilst others reflected changes already in the API system at the time but which had not yet been formally published. Some of the simpler provisions had been modified to reflect the requirements for international harmonization and some to improve correspondence with carefully screened test data. The new formulations, particularly those relating to pressure in combination with other actions/loads, were subject to final adjustment again through use of the screened database. In addition to strength requirements for typical intact structures, ISO 19902 saw the introduction of provisions for grouted and damaged members. Again the final forms of the equations were determined using the screened database. The criteria for screening the test results are discussed, to ensure consistency and relevance of the selected data. The process of selection of the equations for the characteristic values of the formulations, for both single acting and interacting forces, is described. Through comparison with the screened data, each of the formulations can be statistically quantified: the resulting characteristics are reported. At that time, improvements in tubular member effective length determinations had been realized. These were incorporated into the proposed recommendations. Their basis is explained.
Validation of Shiphandling Simulation Models
Authors: Berg Tor E. , Ringen Edvard
Published: November 2011

This paper describes the need for improved methods for validating numerical models used in shiphandling simulators. Such models vary in complexity, from rather simplistic models used for initial shiphandling training at maritime training centers to high-quality models used in the study of advanced marine operations. High-quality simulation models are also used in investigations of maritime accidents such as collisions and groundings. The SIMMAN 2008 conference presented the results of benchmarking studies of simulation tools currently used by research institutes, universities and training centers around the world. Many of these tools employ models based on numerical calculations using methods based on potential or viscous fluid flow, experiments using scale ship models (free running or captive) or semi empirical expressions based on regression analysis of previous model tests. The organizers of SIMMAN 2008 made the hull characteristics of certain ship types available for a comparative study of simulation maneuvering models. The outcome of the benchmark study (using IMO standard maneuvers as case study maneuvers) showed that simulated results varied significantly. In the opinion of the authors, there is an urgent need for new validation studies. The first part of this paper discusses the concepts of simulation model fidelity, verification and validation and the present guidelines issued by ITTC for validation of maneuvering simulation models. The second part looks at the outcomes of the SIMMAN 2008 conference and describes MARINTEK’s contribution to the benchmark study. The use of real-world measurements in model validation is briefly discussed. The need for registration of actual test conditions, as well as the types of tests that should be included in a test scheme, are presented. Finally, the authors discuss validation requirements with respect to the actual application of the selected simulation model as an engineering tool that can be transferred to training simulators used by maritime training centers. It is assumed that simplified simulation models may reduce the quality of simulator based training for ship officers. It is believed that increased quality of simulator model will improve the transfer of training from simulators to real life operations and remove some of the uncertainties related to investigation of maritime accidents.
An Oil Spill and Response Activities Scenarios After the Fuel Tank Seepage in a Port: Haydarpasa Port Case Study
Authors: Koroglu Aysun , Kabdasli M. Sedat
Published: November 2011

Oil spills due to the marine related facilities have been accepted as human sourced catastrophes. The cleanup and recovery from oil spills are generally modeled with the help of numerical models. The type of oil spilled, the water temperature, the dominant winds and currents, and the types of shorelines involved are used as the key parameters of the oil spill modeling systems. The numerical studies are efficiently used to predict the fate of released oil and the containment methods. In this study, several scenarios for the recovery from the oil spill are modeled in Haydarpasa Port as a case study. Haydarpasa port, which is located on the Anatolian side of Bosporus in Istanbul, serves a hinterland for the most industrialized area of Turkey. Both the oil spill and the response activities scenarios are modeled using OILMAP™ Version 6.1. Surface Trajectory Model and the Stochastic Model for seepage from the fuel tank for varying spill duration periods and for the same environmental conditions. In this study, seepage from a fuel tank and the most efficient response activity in a port are modeled as an emergency plan in Haydarpasa port as a case study.
Reverse Simulation for Specifying the Source of Pollutants in Waters
Authors: Kitazawa Daisuke , Abe Satoshi , Hamba Fujihiro , Kato Shinsuke
Published: November 2011

Reverse simulation was carried out to specify the point source of pollutants in closed waters. If pollutants flow out into waters, their source must be specified as soon as possible to take a quick measure against the pollution problem. Actually, a wide variety of pollutants have been released into the aquatic environment, some with catastrophic consequences for aquatic life or man. Numerical simulation is one of the powerful tools to specify the point source of pollutants. An inverse trajectory analysis has been used in the case when an advective process of pollutants is dominant. However, the inverse trajectory analysis does not take the diffusion of pollutants into account. Several analytical techniques are applicable only to simple current fields. The present study proposes reverse simulation to specify the point source of pollutants. The basic equation of the reverse simulation is given by changing the positive time derivative term of the advection-diffusion equation of pollutants into a negative term. First, numerical simulation was executed in a forward direction. The results of water current velocities were preserved for the following reverse simulation. Assuming that the pollutants are subject to the surrounding water current and turbulence like a tracer, the advection and diffusion processes of the tracer could be solved for obtaining the initial condition of reverse simulation, and for the following comparison with the results of reverse simulation. The predicted result of water current velocities in the forward simulation was given to calculate the advection-diffusion equation of the tracer. One of the major problems of reverse simulation is the instability of numerical simulation. A Gaussian filter was used for the spatial distribution of the tracer or of the flux of the tracer to eliminate the numerical instability, and the optimum filter width was discussed. As a result, the instability of reverse simulation was suppressed by applying the Gaussian filter for the spatial distribution of the tracer. However, the concentration of the tracer was not condensed in comparison with the result of the tracer in the forward simulation. When the Gaussian filter was used for the special distribution of the flux of the tracer, the accuracy of the prediction of the point source was improved. This is because the high frequency variation was suppressed, keeping the low frequency variation. The concentration of the tracer was more condensed with smaller filter width in both cases. The future studies are to determine the filter width adequately and to modify the difference equation of the Gaussian filter.
Reliability Assessment of TLP Air-Gap in Nonlinear Waves
Authors: Bitner-Gregersen Elzbieta M.
Published: November 2011

The present study demonstrates effects of the CresT JIP (Cooperative Research on Extreme Seas and their impacT) findings regarding extreme and rogue waves through a simplified structure reliability analysis of a generic TLP structure defined by the project. The study demonstrates effects of wave nonlinearity beyond the second order, diffraction-radiation of incoming waves with the structure, spatial variations of crest statistics, a vertical displacement of the TLP system at the deck location as well as sea water level variations due to surge and tide. In order to account for these effects a stochastic model is suggested. Sensitivity studies are carried out to identify importance of analysed parameters and their stochastic behaviour to the failure probability. Uncertainties related to the analysis are identified and ranked given special attention to the effect of wave nonlinearities beyond the 2nd order. Recommendations for future research needs are suggested.
Towards the Navigational Safety Standard in Close Proximity Underway Lightering Maneuvers of Two Ships
Authors: Skejic Renato , Kirimoto Kensuke , Berg Tor E. , Pedersen Egil
Published: November 2011

The development of a generalized navigation safety standard for ships performing underway lightering maneuvers in close proximity has been considered from an operational viewpoint. In general, it is well known that the safety and efficiency of a maritime operation between two ships at close range represents a challenging and demanding task to mariners. The main reason is related to unfamiliar maneuvering behavior of the involved ships and consequently a poor decision-making process due to lack of knowledge and understanding of ship-to-ship interaction effects. Operational challenges in ship-to-ship lightering can be reduced through an increased knowledge and understanding of the hydrodynamic interaction effects. This paper discusses how to perform the lightering maneuver in the final approach phase until the lateral distances are reduced to the fender diameter. Visualization of ‘Collision Danger Zones’ due to hydrodynamic interaction is proposed to be introduced in a decision-support tool to assist the pilot/master to control the approach phase of the ship-to-ship operation and thus improve the overall operational safety.
Installation of a Submerged Buoy for Supporting Risers (BSR) System in Campos Basin Site
Authors: de Arau´jo Jairo Bastos , de Almeida Jose´ Carlos Lima , Fernandes Antonio Carlos
Published: November 2011

The BSR (Buoy for Supporting Risers) concept is composed by a submerged buoy anchored to the sea bottom by tethers and intended to support risers coming from the bottom (probably SCRs — Steel Catenary Risers) and going to the floating platform (probably with flexible jumpers). For the case under analysis here, the main dimensions of the BSR prototype are 27.2 m length × 27.2 m width × 5.0 m depth. The paper describes all final full scale installation step so that the BSR may be considered a suitable technology. The installation indeed was the great challenge of this design due the size of the hull. The present work also evaluates numerically and experimentally a specific new manner to install the BSR with the support of auxiliary mooring lines among with the four tethers connected to it. One of the installation premises was to make use of Anchor Handling Supply Vessels instead of Crane Vessels. After this numerical analysis, the work went on by performing model tests that simulates the operation in a deep water model basin using 1:40 scale. The model test anticipated several problems such as the chain stopper weakness in the operation and others as discussed in this paper. As a conclusion the work was devised the most important parameters during the system installation and suggested ways to improve the methodology. In November 2009 the BSR was installed in 500 m of water depth at Congro field location, Campos Basin, offshore Brazil. The tethers were adjusted in January 2010 and in March 2010 two risers were installed. Thenceforward the last edge of this knowledge was considered over passed.