bluuebunny/crossref_metadata_2025 huggingface dataset:
Environmental Characterization of Ash From the Combustion of Wood and Tires for Beneficial Use in Florida
Authors: Tolaymat Thabet , Townsend Timothy
Published: January 2009

Non-hazardous industrial solid wastes are frequently proposed for beneficial use rather than being disposed in MSW landfills. An example of such an industrial waste is waste-to-energy (WTE) ash. Proposed beneficial use projects for WTE ash often involve some form of land application. Prior to the land application of any solid waste, the possible risk to human health and the environment should be assessed. The Florida Department of Environmental Protection (FDEP) has developed a beneficial use guidance document that provides WTE ash generators with the testing requirements that must be demonstrated before a particular beneficial use scenario is determined appropriate (FDEP 2001). For WTE ash to be deemed safe for land application, the risk associated with two separate pathways should be assessed: direct human exposure and the contamination of groundwater via leaching. While organic pollutants (e.g. dioxins) might be a concern, heavy metals are typically the pollutants that most limit the potential for reuse; heavy metals are the focus of the discussion in this paper.
Ways to Improve the Efficiency of Waste to Energy Plants for the Production of Electricity, Heat and Reusable Materials
Authors: Zwahr Heiner
Published: January 2009

Up to now the emissions of waste-to-energy plants have been of major concern for the operators of waste incineration plants and the public. In Germany the emission standards for waste incineration plants have been very strict for more than 10 years, more stringent than for coal fired power plants, for example. Now the member states of the European Union are following suit with the same standards in accordance with European directive 2000/76/EC on the incineration of waste. Within a couple of years all European waste incineration plants will have to comply with the emission limits of directive 2000/76/EC. There is also legislation in the pipeline restricting landfilling of untreated waste. In view of the discussions about CO2 reductions the efficiency of today’s Waste to Energy (WTE) plants should be improved, even though — or rather because — waste is regarded to some extent as “green power”. With the same goal in mind the recovery rate of reusable materials from the incineration of waste or flue gas treatment should be improved. This will make it possible to reduce the amount of CO2 generated by the production of these materials from natural resources and to conserve natural resources.
Recycling and Waste-to-Energy: On-Going Compatibility Success
Authors: Kiser Jonathan V. L.
Published: January 2009

This paper will discuss findings from the 2002 nationwide survey that was aimed at determining how well recycling and waste-to-energy are working together. It represents a ten-year update to the original research completed for the Integrated Waste Services Association in Washington. The 2002 survey confirmed not only that recycling and waste-to-energy are compatible, but also provided solid reasons why the two technologies perform better together than separately. This paper highlights these reasons and also features select compatibility case studies from communities around the United States.
Development of Structural Steel With Superior Resistance Against Fatigue Crack Growth: Part II
Authors: Konda Noboru , Arimochi Kazushige , Hirota Kazuhiro , Watanabe Eiichi , Tada Masuo , Kitada Hiroshige , Fukui Tsutomu , Yamamoto Motomichi , Kho Yunbo , Yajima Hiroshi
Published: January 2009

The fatigue crack problems that broke out at the end of the twentieth century were fatigue crack properties in hull structures. This motivated research on a lot of technologies against fatigue fracture. It was clarified that the detection of fatigue crack initiation in complex welded structures like hulls is quite difficult, and that the crack length at recognition is mostly long compared to mechanical parts. From these research results, not only stress reduction at critical areas by improvement in design but also newly developed materials with excellent resistance to fatigue crack growth has been desirable for structural integrity. The newly developed structural steel, in which fatigue crack growth resistance is controlled by microstructures, will be introduced in this report. Various fatigue properties of the base steel plates in air and in synthetic sea water are compared. And the fatigue life extension effects by FCA is observed in fatigue tests of welded joints and welded structural models.
Testing of Segment Specimens and Full Scale Pipes for the Assessment of Fracture During Reeling Installation
Authors: Wa¨stberg Stig
Published: January 2009

This Paper describes the testing of Segment Specimens and Full Scale Pipes carried out at DNV within the Joint Industry Project “Fracture Control for Installation Methods Introducing Cyclic Plastic Strain – Development of Guidelines for Reeling of Pipelines”. The JIP was a cooperation between DNV, TWI and Sintef. A total of 24 full thickness Segment Specimens, with cracks/notches introduced in the Base Metal, Fusion Line Root and Fusion Line Cap, were tested. The specimens were loaded both monotonically and cyclically, simulating reeling installation. Two Full Scale Pipes were subjected to a bending loading program simulating a reeling installation. Each pipe contained three test welds and cracks/notches were introduced both at the 6 o’clock and the 12 o’clock positions, i.e. six cracks/notches in each pipe. In one pipe the cracks/notches were introduced in the Weld Metal and in the other in the Fusion Line from the Cap side. After the loading program all the cracks/notches were broken open and the stable crack growth were measured and compared to predictions based on fracture mechanics principals (essentially following BS 7910-1999). A method for adjusting the analysis procedure, in order to obtain good agreement between the predictions and the experimental observations, is suggested. The JIP also included Materials Testing and FEM Analyses. A Guideline Document was developed which is currently being used by the project participants and it is the intention to issue a DNV Recommended Practice in support of the DNV Offshore Standard OS-F101 “Submarine Pipeline Systems – 2000” based on the experience gained and feed back received from the participants. The Guideline document is described in another paper (OMAE2004-51061) at the conference.
Wave Slamming Forces on Horizontal Circular Cylinders in Intertidal Zone
Authors: Hariprasad V. , Neelamani S. , Sundaravadivelu R.
Published: January 2009

Wave forces on slender horizontal and vertical cylinders are normally estimated using Morison equation (1950). When a cylinder is near the free surface, it experiences the slamming force. Wave slamming on horizontal cylinders of any ocean structure is crucial to its design. API Recommended Practice 2A-WSD (2000) recommends slamming coefficient Cs equal to π for circular cross sectional cylinders near the still water level. The shape of the member (circular, rectangular or square) is also expected to alter the values of Cs. The horizontal cylinders in the inter tidal zone for Port craft jetties are subjected not only to slamming force in the vertical direction but also to berthing force in the horizontal direction. If two cylinders are kept in close spacing, then the load on both cylinders will differ compared to force on a single cylinder. The effect of tidal variation on slamming forces needs thorough investigation. The comparison of single circular cylinder and twin circular cylinder with a clear spacing equal to diameter of cylinder in regular waves is discussed in this paper.
Numerical Prediction of the Effects of Oceanic Flow Characters on the Evolution of CO2 Eniched Plumes
Authors: Chen Baixin , Song Yongchen , Nishio Masahiro , Akai Makato
Published: January 2009

The near-field dynamics of CO2 rich plume draw attention of assessment of the local impacts of CO2 ocean sequestration on natural oceanic environment. In this study, we attempt to predict numerically the role of ocean flow characters, including the current profile and the turbulent intensity, and of the injection parameters, including the injection rate and initial droplet diameters, on the evolution of liquid CO2 (LCO2) droplet and CO2 enriched seawater plumes. The numerical model we used in this study is a two-phase large-eddy simulation model. From numerical experiments we found: 1). The plume height (both LCO2 plume and CO2 enriched seawater plume) is insensitive to ocean currents and turbulent intensity but do sensitive to initial droplet diameter. For releasing rates of 0.6kg/sec, the estimated plume heights at initial droplet diameters of 8.0 and 5.0 millimeter are approximately 170 and 80 meters for different oceanic flows. 2). The physics of CO2 enriched seawater plume, for instance CO2 concentration distribution and local largest concentration, however, are governed sensitively by seawater flow characters and alternatively by injection rate and initial droplet diameter. 3). Strong turbulence enhanced the dispersion and mixing of droplets and CO2 enriched seawater with fresh seawater to produce an improved CO2 concentration distribution.
Design and Testing of Large Diameter Composite Reinforced Pressure Vessels for Offshore Gas Applications
Authors: Wolodko John , Zimmerman Tom , Stephen Gary , Cano Greg , Fawley Norman
Published: January 2009

Bulk transportation of compressed natural gas is becoming a viable and flexible option for moving stranded gas reserves to existing or remote markets. One such technology that is currently being developed for this application is the Gas Transport Module (GTM™). Gas Transport Modules are large diameter, high pressure, fiber reinforced composite/steel pressure vessels intended for the mobile transport of natural gas on a variety of carriers including ships, barges, trucks and trains. The purpose of this paper is to discuss recent work concerning the design and testing of these large diameter, composite pressure vessels. The advantages of the proposed hybrid composite/steel design for offshore use are discussed. An overview of current standards development, specialized analysis methods and testing requirements is also provided.
Coupled Motion Analysis of a Semisubmersible Platform in Campos Basin
Authors: Roveri Francisco Edward , Rodrigues Marcos Vinicius , Jacob Breno Pinheiro
Published: January 2009

This work describes the generation of numerical models for the coupled analysis of a semisubmersible platform to be installed in Campos Basin, and presents the results, in terms of platform motions, of a set of analyses under fatigue environmental loading cases. The coupled model comprises the hull, the mooring lines, and all risers connected to the platform. The model includes also a FSHR (Free Standing Hybrid Riser) system to be connected to the platform; this system is composed by a rigid riser, an air can and a flexible jumper. A set of environmental loading cases appropriate for fatigue analyses is defined, in terms of current profile, irregular bi-directional seastate, and wind. For each loading case, nonlinear time-domain dynamic analyses are performed employing the Prosim program. This program is based in a coupled formulation that incorporates, in a single code and data structure, a hydrodynamic model to represent the hull, and a finite element model to rigorously represent the structural/hydrodynamic behavior of the lines. At every time step of the time integration of the equations of motion representing the hull, a series of nonlinear dynamic analysis of the lines is performed following a subcycling procedure. The results of the coupled analysis are expressed as time histories of platform motions. The next step is to proceed to the treatment of these time series, in order to determine, for each loading case: a) The frequency spectra of each motion component; and b) Representative statistical values in terms of static offsets, first and second-order motions (standard deviations and periods for low-frequency and wave-frequency motions). The platform motions that result from the coupled analyses presented in this work can be employed to perform the detailed structural analysis of the FSHR system, by employing an isolated model of the riser in a specialized program.
Investigation of the Flow Around Two Circular Cylinders Employing the Spectral Element Method With Modal Decomposition
Authors: Carmo Bruno Souza , Meneghini Julio Romano , Jabardo Paulo Jose Saiz , Saltara Fa´bio
Published: January 2009

Flow induced vibrations play an important role in the process of fatigue in cylindrical elements of offshore platforms. One of the main sources of vibration is due to vortex shedding. Such vortices are originated from the separation of the boundary layer and the low-pressure regions cause the hydrodynamic forces to oscillate. This kind of vibration is known in literature as vortex-induced vibration (VIV), and it has some points that are not well understood yet. When a circular cross section is considered, the point of separation changes with the Reynolds number, increasing the complexity of the phenomena. Additionally, when two bluff bodies are disposed near each other, the vortices shed by one of them can reach the other, interfering with the vortex formation close to the later, and constituting another source of vibration. This work is an effort to provide a better comprehension of the vortex-induced vibration phenomena in a flow around groups of cylinders. In this paper, a detailed computational study of the flow around two rigid cylinders in a tandem arrangement is carried out. The spectral/hp element method is used in the simulations, with a modal decomposition in the span direction. The three-dimensional structures in the wake are analysed, and the level of synchronization of the flow along the span is verified for a gap of five diameters between the cylinders.
Coupled Nonlinear Barge Motions: Part II — Deterministic Models, Stochastic Models and Stability Analysis
Authors: Yim Solomon C. , Nakhata Tongchate , Huang Erick T.
Published: January 2009

A computationally efficient quasi-two-degree-of-freedom (Q2DOF) stochastic model and a stability analysis of barges in random seas are presented in this paper. Based on the deterministic 2DOF coupled Roll-Heave model with high-degree polynomial approximation of restoring forces and moments developed in Part I, an attempt is made to further reduce the DOF of the model for efficient stochastic stability analysis by decoupling the heave effects on roll motion, resulting in a one-degree-of-freedom (1DOF) roll-only model. Using the Markov assumption, stochastic differential equations governing the evolution of probability densities of roll-heave and roll responses for the two low-DOF models are derived via the Fokker-Planck formulation. Numerical results of roll responses for the 2DOF and 1DOF models, using direct simulation in the time domain and the path integral solution technique in the probability domain, are compared to determine the effects of neglecting the influence of heave on roll motion and assess the relative computational efforts required. It is observed that the 1DOF model is computationally very efficient and the 2DOF model response predictions are quite accurate. However, the nonlinear roll-heave coupling is found to be significant and needs to be directly taken into account rendering the 1DOF roll-only model inadequate for practical use. The 2DOF model is impractical for long-duration real time response computation due to the insurmountable computational effort required. By taking advantage of the observed strong correlation between measured heave and wave elevation in the experimental results, an accurate and efficient Q2DOF model is developed by expressing the heave response in the 2DOF model as a function of wave elevation, thus reducing the effective DOF to unity. This Q2DOF model is essential as it reduces the computational effort by a factor of 10−5 compared to that of the 2DOF model, thus making practical stochastic analysis possible. A stochastic stability analysis of the barge under operational and survival sea states specified by the US Navy is presented using the Q2DOF model based on first passage time formulation.
Environmental Contour Lines for Design Purposes: Why and When?
Authors: Haver Sverre , Kleiven Gudmund
Published: January 2009

Methods of prediction of structural loads corresponding to a required target annual exceedance probability are reviewed. Particular attention is given to utilization of environmental contour lines for such a purpose. This approach is based on using short term methods for predicting adequate estimates of the q-probability response. The environmental contour line approach is a very convenient approach if complicated structural problems are considered. For such problems one will often have to involve numerical time domain analyses or model tests to reveal the short term probabilistic structure of the response maxima, making a full long term response analysis impossible for most practical problems.
Effect of Wave Induced Loading and Line Loading in Fully Stochastic Fatigue Assessment for West Africa FPSO
Authors: Park T. H. , Lee J. H. , Cho J. W. , Shin H. S.
Published: January 2009

The fatigue assessment for a caisson of the interface between a caisson and a FPSO hull has been performed based on the FMS (Fatigue Methodology Specification) [1]. Investigation is focused on the various loading effects including inertia loading due to ship motions from a site specific swell, sea and line loading from the submerged caisson connected to the side shell of FPSO. The fully stochastic method was used for estimating damage levels from wave loadings. The component-based method was used for line loading effects. The two kinds of results from each case were combined the variance and mean period combination. For the inertia loading, it is shown that a hull deforming due to vertical bending moment is the principal effect for a fatigue assessment. For the line loading, it is found that the loading effect due to the submerged piping system connected to the side shell of FPSO is not significant for the fatigue of the side shell supporting structure. In conclusion, the fatigue damage from the site-specific swell is dominant effect among overall fatigue damage components of FPSO in the specific site condition of West Africa.
A Comparison of Methods for Assessing the Lifetime Reliability of a Moored FPSO
Authors: Grime Andrew J. , Langley R. S.
Published: January 2009

Current design codes for floating offshore structures are based on measures of short-term reliability. That is, a design storm is selected via an extreme value analysis of the environmental conditions and the reliability of the vessel in that design storm is computed. Although this approach yields valuable information on the vessel motions, it does not produce a statistically rigorous assessment of the lifetime probability of failure. An alternative approach is to perform a long-term reliability analysis in which consideration is taken of all sea states potentially encountered by the vessel during the design life. Although permitted as a design approach in current design codes, the associated computational expense generally prevents its use in practice. A new efficient approach to long-term reliability analysis is presented here, the results of which are compared with a traditional short-term analysis for the surge motion of a representative moored FPSO in head seas. This serves to illustrate the failure probabilities actually embedded within current design code methods, and the way in which design methods might be adapted to achieve a specified target safety level.
Penguins Flowline Lateral Buckle Formation Analysis and Verification
Authors: Matheson Ian , Carr Malcolm , Peek Ralf , Saunders Paul , George Nigel
Published: January 2009

The Penguins pipeline is a 60 km PIP system designed to buckle laterally on the seabed. The pipeline has been laid in a snaked shape in order to initiate regular lateral buckles. However there is significant uncertainty over the buckle formation process and concern over the robustness of the snake lay approach. A detailed as-laid ROV survey was undertaken to define the geometry of the pipeline system. This has been supplemented by two high precision ROV surveys of the pipeline in the operating configuration. This paper outlines how the buckling uncertainty was addressed at the design stage, the as-laid stage, and finally compares the predictions with the actual observations of lateral buckles in the operating flowline.
Safety of Dynamic Positioning Operation on Mobile Offshore Drilling Units
Authors: Chen Haibo , Moan Torgeir , Verhoeven Harry
Published: January 2009

Safety of dynamic positioning operation on mobile offshore drilling units is characterized by two key parameters, namely, the resistance to loss of position, and the robustness of recovery. Both parameters should be evaluated in order to identify effective ways to further improve the safety. The failure modes, applicable frequencies, and probabilistic modeling for both loss of position and recovery are discussed in this paper. Influencing factors to the resistance and robustness parameters are identified respectively. The results contribute to the further development of the safety assessment methodology for DP operation on drilling units. Areas that need further development of modeling approach and analyses are pointed out.
Station-Keeping Tests of Moored Caisson in Strong Current
Authors: Chakrabarti Subrata K. , McBride Mark
Published: January 2009

A new suspension bridge is being built over the Tacoma Narrows, Washington. The bridge will be placed on a structure mounted on two large concrete caissons. The caissons are being constructed in a floating position by pouring concrete at site. During this construction period, the floating caissons are moored in place and will be subject to high currents in the Narrows at a range of drafts. In order to investigate the motions of the caisson and the mooring line loads, physical model tests were performed at a scale of 1:100 at HR Wallingford (HRW). The actual bottom contours of the Narrows near the construction site was duplicated in the model. The catenary mooring lines were highly nonlinear. The current forces and moments on the floating caisson included steady and oscillating components due to flow separation and vortex shedding. There is an existing bridge mounted on two piers in the vicinity of the new caissons, which introduced an appreciable flow interference effect. The tests were conducted in both the ebb and flood flow directions so that the effect of the shadowing of the caisson-pier pair could be studied in the tests. The recorded results of the elastic mooring tests were compared in terms of the maximum measured tensions with a time-domain dynamic motion simulation program, MOTSIM. The results of this comparison are presented in this paper.
Conditional Short-Crested Second Order Waves in Shallow Water and With Superimposed Current
Authors: Jensen Jo̸rgen Juncher
Published: January 2009

For bottom-supported offshore structures like oil drilling rigs and oil production platforms, a deterministic design wave approach is often applied using a regular non-linear Stokes’ wave. Thereby, the procedure accounts for non-linear effects in the wave loading but the randomness of the ocean waves is poorly represented, as the shape of the wave spectrum does not enter the wave kinematics. To overcome this problem and still keep the simplicity of a deterministic approach, Tromans, Anaturk and Hagemeijer (1991) suggested the use of a deterministic wave, defined as the expected linear Airy wave, given the value of the wave crest at a specific point in time or space. In the present paper a derivation of the expected second order short-crested wave riding on a uniform current is given. The analysis is based on the second order Sharma and Dean shallow water wave theory and the direction of the main wind direction can make any direction with the current. Numerical results showing the importance of the water depth, the directional spreading and the current on the conditional mean wave profile and the associated wave kinematics are presented. A discussion of the use of the conditional wave approach as design waves is given.
Building a Global Resource for Rapid Assessment of the Wave Climate
Authors: de Valk Cees , Groenewoud Peter , Hulst Sander , Klopman Gert
Published: January 2009

In order to provide rapid access to reliable wave and wind climate information worldwide, a resource has been created combining: • a global offshore wind- and wave data-base, currently containing calibrated and validated spectral wave data from a wave hindcast model as well data from several satellite microwave sensors; • a simple but effective numerical model to predict nearshore wave conditions from the offshore spectra; • analysis tools to extract various climate parameters from the data such as scatter tables, extreme value analysis and persistency; • a web interface giving instantaneous access to the most commonly needed information. The resource is primarily intended for use in planning and design of operations typically requiring five years of data, but it an also be used for the design of certain structures, as there are now 16 years of significant wave height data from satellite radar altimeter available. This paper describes the components of the system and discusses their merits and limitations. We also present some results of the validation of the global satellite wave and wind data, of the global and regional wave model hindcasts, and of the nearshore wave transformation employed to obtain wave climate at sheltered or shallow-water sites.
Structural Reliability Criteria for Control of Large-Scale Interconnected Marine Structures
Authors: Berntsen Per Ivar Barth , Leira Bernt J. , Aamo Ole Morten , So̸rensen Asgeir J.
Published: January 2009

In this paper, we develop a model of a futuristic fish farming structure, and study problems related to interconnected marine structures and strategies for configuration control with focus on structural reliability. Configuration control refers to positioning of individual modules or the entire structure as a whole. The structure is a chain of surface vessels, moored to the seabed via a spread mooring system connected to the front vessel. In this paper we design a control system that: 1) Ensures limited loading of the mooring system in order to avoid mooring cable failure and;2) Ensures positive strain in the connectors between vessels in order to avoid buckling effects due to variations in for instance the current. Control actuation is by means of a thruster mounted on the first module. The performance of the control system is demonstrated by simulations.
2D Experimental Study of Waves and Current Contribution to the Nearbed Velocities and Shear Stresses Field
Authors: Delgado Blanco M. R. , De Mulder T. , Willems M. , Banasiak R. , Verhoeven R. , Monbaliu J.
Published: January 2009

Most of what is known about flow under waves and currents has been deduced from numerical models and not always validated. Absence of accurate experimental and field data, including measurements within the boundary layer or in its vicinity, makes the observation and study of the interaction between steady and oscillatory flow together with model validation difficult. A series of 2D experiments has been done in a laboratory flume. Velocity profiles obtained under different conditions have been analyzed. In addition, a simple 1DV model for turbulent boundary layer simulation has been used. Computed near bed velocities and roughness length are compared with experimental results. By means of three methods based on experimental and numerical results, variations of friction forces as a result of the interaction between the oscillatory and the steady components are evaluated.
Operational and Start-Up Experiences for First Arctic Offshore Island Facility: BP Northstar Project
Authors: Summers Steven M.
Published: January 2009

An overview of unique challenges associated with operating offshore facilities in an Arctic environment is discussed using the BP Northstar development as the topic. Northstar is located 6 miles offshore in the Beaufort Sea of Alaska. This paper briefly addresses challenges faced by developments of this type in environmentally sensitive areas as well as unusual construction and operating issues which do not arise in traditional offshore designs. This paper would be of interest to those who are considering or are engaged in similar cold region offshore developments.
Development of Natural Gas Liquefaction FPSO
Authors: Masanobu Sotaro , Kato Shunji , Nakamura Arata , Sakamoto Takashi , Yoshikawa Toshio , Sakamoto Atsushi , Uetani Hideo , Kawazuishi Kenichi , Sao Kunihisa
Published: January 2009

Natural gas is abundant and is cleaner than petroleum. Therefore, demand for natural gas is expected to grow significantly. However, the means of transporting natural gas is presently limited to pipelines and LNG tankers, thereby making its wider use unlikely. There are substantial numbers of known gas reservoirs that are difficult to develop utilizing current transportation means because of constraints such as the scale of gas fields, water depth, distance to shore, and distance from markets. A new, economical, reliable development technique or transportation means is required for developing such gas reservoirs. Ministry of Economy, Trade and Industry (METI), Japan National Oil Corporation (JNOC) and private corporations have jointly investigated the Natural Gas Liquefaction Floating Production, Storage and Offloading (NGL-FPSOs) units to effectively develop gas reservoirs by converting the gas into NGL. This paper presents the background on NGL-FPSO development and findings on its application.
Simplified Model for Evaluation of Fatigue From Vortex Induced Vibrations of Marine Risers
Authors: Baarholm Gro Sagli , Larsen Carl M. , Lie Halvor , Mo̸rk Kim , Meling Trond Stokka
Published: January 2009

This paper presents a novel approach for approximate calculation of the fatigue damage from vortex-induced vibrations (VIV) of marine risers. The method is based on experience from a large number of laboratory tests with models of full-length risers, large-scale tests and also full-scale measurements. The method is intended to provide a conservative result and be used for screening purposes at the early design stage. The model is in particular aimed at predicting fatigue for risers that respond at very high mode orders (above 10), but may as well yield valid results for lower mode numbers. The model will, however, not be adequate for free span pipelines or other structures that normally will respond at first and second mode. The riser will be defined in terms of some key parameters like length, weight, tension, hydrodynamic diameter and stress diameter. A current profile perpendicular to the riser in one plane must be known. The program will apply a simple model for calculation of eigenfrequencies and mode shapes, and these are sorted into in-line (IL) and cross-flow (CF) bins. An effective current velocity and excitation length can be defined from the profile and will be applied to identify the dominating cross-flow response frequency and the total displacement rms value. The dominating in-line response frequency is taken as twice the cross-flow frequency, and inline response rms is taken as a given portion of the cross-flow rms value. A set of contributing modes is defined from an assumed frequency bandwidth that reflects observed bandwidths, but also modal composition for cases with discrete frequency response. A simple mode superposition technique is then used to find the set of modes that gives the identified rms values. Bending stresses will be found directly from the curvature of the mode shapes. Fatigue damage will be found from stress rms values, user defined stress concentration factor and given SN curves. The model has been implemented in a simple computer program and verified by comparing results to measurements. The ambition has not been to obtain an exact match between computed results and observations, but to verify that the model gives reasonable but conservative results in almost all cases. However, an unrealistic over prediction of the fatigue damage is not desired. The results are promising, but the need for more information from measurements and response analyses with programs like VIVANA and SHEAR7 is still obvious.
A Research on Characteristics of Responses of a Floating Structure in Tsunami
Authors: Masuda Koichi , Ikoma Tomoki , Uchida Maki , Takeda Akira
Published: January 2009

The objective of present paper are to establish the practical numerical analysis system for responses of motions and mooring forces on a floating structure induced by Tsunami and to clarify the characteristics of responses on floating bodies in tsunami. In the present analysis system, the initial tsunami profile is evaluated by Mansinha-Smylie’s Method and propagating tsunami profiles are calculated by linear long wave theory and also the tsunami exciting forces on floating body are computed by the numerical wave tank based on VOF method [5] and then the motions and mooring tether forces due to Tsunami on floating body are predicted by the convolution integral method. The usefulness of present system is confirmed by comparing with the experimental results on Tsunami exciting forces on floating bodies. The responses of floating body due to tsunami using fault models of Tokai and Tonankai earthquakes are computed by using the present simulation system so that the characteristics of responses on floating bodies are examined and are clarified.
Survey and Inspection Management for FPSOs
Authors: Biasotto Paulo , Rouhan Antoine
Published: January 2009

Survey and inspection campaigns are important inputs in the Asset Integrity Management System (AIM) of FPSOs and other floating offshore facilities. Considering that the unit shall stay at site during the whole life of the field where the disconnection or the removal of the mooring system are not planned, a comprehensive methodology for the survey and inspection of the unit during this period shall be provided and subject to review based on the results of the scheduled inspections. So further than subjected to class and statutory requirements, inspection and survey plans shall reflect the required availability and durability of the unit regarding the field life. Among the several degradation mechanisms covered by the inspection and survey plans, fatigue is an important issue to check carefully. Risk Based Inspection Methodology has been adopted in several projects and is an important tool to establish rational inspection campaign for structural components, mainly for those located in areas where access is critical and operational constraints are an important parameter. The aim of this paper is to present the methodology to establish inspection and survey plans, combining RBI analysis and the industry expertise. The several steps to achieve the final inspection campaign are described based on the experience on new-built but also converted FPSOs.
Numerical Analysis for Hydrodynamic Motions of Floating Structure Using MPS Method
Authors: Maeda Hisaaki , Nishimoto Kazuo , Masuda Koich , Asanuma Takayuki , Tsukamoto Marcio Michiharu , Ikoma Tomoki
Published: January 2009

The authors started this research on estimation method of responses for floating structures using Computational Fluid Dynamics (CFD). This paper is first step, which has potential to be very valuable to the engineering community. The numerical method used in this study is the Moving Particle Semi-implicit (MPS) method 1) 2), which is based on particles and their interactions. MPS method that was developed recently is one of particle method. The particle number density is implicitly required to be constant to satisfy incompressibility. A semi-implicit algorithm is used to for two dimensional incompressible non-viscous flow analysis. The particles whose particle number densities are below a set point are considered as on the free surface. In this paper, first, the authors explain the outline of MPS method that Kshizuka et al. developed. You can see more details of this method by references. And the calculation test of column collapse problem is carried out to check our code that we developed. Second, the modeling of free surfaces is explained. And the authors proposed the way to skip irregular data of wave height. Validation of wave profiles was carried out comparing Stokes theory. Third, calculation results of floating body are showed. This method of calculating response of floating structure is by Koshizuka et al. 3). Finally, the authors show calculation results of wave exciting forces by MPS method comparing singular point distribution method (SDM).
Routes to Large Amplitude Motions of Mooring Systems Due to Slowly-Varying Drift
Authors: Matsuura Joa˜o Paulo J. , Bernitsas Michael M.
Published: January 2009

The effect of second-order slowly-varying wave drift (SVWD) forces on the horizontal plane motions of moored floating vessels has been studied for nearly 30 years. Large amplitude oscillations of moored vessels have been observed in the field or predicted numerically. Often, those have been incorrectly attributed to resonance or time-varying excitation from current/wind. In previous work, the authors have shown that resonance is only one of numerous interaction phenomena, and that large amplitude oscillations can be induced by SVWD forces or even time independent excitation. Currently, there is no mathematical theory to study stability and bifurcations of mooring systems subjected to nonautonomous spectral excitation. Thus, in this paper, bifurcation boundaries are approximated by analyzing simulation data from a grid of points in the design space. These boundaries are plotted in the catastrophe sets of the corresponding autonomous system, for which a design methodology has been developed at the University of Michigan since 1985. This approach has revealed a wealth of dynamics phenomena, characterized by static (pitchfork) and dynamic (Hopf) bifurcations. Interaction of SVWD forces with the Hopf bifurcations may result in motions with amplitudes 2–3 orders of magnitude larger than those due to resonance. On the other hand, in other cases the SVWD/Hopf interaction may reduce or even eliminate limit cycles.
Latest Findings in the Development of Rules for Design and Evaluation of Marine Pipelines in the Gulf of Mexico
Authors: Rommel Burbano B. N. , Said Ramirez S. , Leonel Lara M.
Published: January 2009

The paper presents the work carried out by the Instituto Mexicano del Petro´leo (IMP) during the last years, regarding the development of local rules for the design and reassessment of marine pipelines, taking into account environmental and operational conditions in the Gulf of Me´xico, as well as economic implications of these facilities within Mexican social and political fields. The costs for Petro´leos Mexicanos (Pemex) of a possible failure of a marine pipeline are also considered. The results will be incorporated in a Norm of Reference to Pemex being the first regulating national document in this area. This work is based in an extensive risk study of the marine pipelines and risers. The costs are evaluated regarding the failure consequences that could be present in the marine pipelines both during the installation phase as well as during the operation phase. The failure probabilities and the reliability indexes are determined according to the production and the type of product. Using structural reliability theory, a classification by service and safety (CSS) for the marine pipelines is obtained and from that the safety factors for design and evaluation for all the possible loads that may be present during both installation and operation. The methodology used is according to the state of the art and with international codes (API and DNV). The main advantage of the project is to better understand the behavior of the marine pipeline and risers taking into account the geotechnical and ocean characteristics of the Gulf of Me´xico and the costs that would represent for Pemex the possible failure of a structure of this type.
The Simplified Method for the Wave Loads Statistical Characteristics Estimation in Stationary Confused Seas
Authors: Davydov I. F. , Egorov G. V. , Kozlyakov V. V.
Published: January 2009

Practically relevant procedures of construction of the short-term and long-term distributions of wave loads and combined stresses at two- and three-dimensional waves is based on the rather cumbersome schemes of definition of the standards “σyi”, effective periods “Tyie” and correlation coefficients “ryiyi” of wave loads “yi”. These calculations can be made more visible and essentially simplified on the basis of the shape stability of the doubly-normalized amplitude-frequency (AFC) and mutual-frequency response characteristics (MFRC). All specific features of these characteristics are determined by their maximum values and frequencies of maxima. In the report the convenient formulae for estimation of σyi, Tyie and ryiyj are derived, and graphs of functions, determining them, for different wave loads are plotted. These relations allow to reveal major influencing factors and use them for construction of the short-term and long-term spectra of wave loads and stresses for full transport ships (CB > 0.75), including FPSO ships, for which non-linear and dynamic effects are expressed rather weakly.
A Composite Rigid Body Algorithm for Modeling and Simulation of an Underwater Vehicle Equipped With Manipulator Arms
Authors: Amir Hosseini Mohammad Khalaj , Banae Mohammad , Meghdari Ali
Published: January 2009

In this paper modeling and simulation of an underwater vehicle equipped with manipulator arms, using Composite Rigid Body (CRB) algorithm will be discussed. Because of increasing need to Unmanned Underwater Vehicles (UUVs) in oil and gas projects in Persian Gulf, for doing operations such as inspection of offshore jackets, subsea pipelines and submarine cables and also pre installation survey and post laid survey of submarine pipelines and cables, design and construction of “SROV” was developed in Sharif University of Technology, and at design stage behavior of underwater vehicles was studied. In this paper, an efficient dynamic simulation algorithm is developed for an UUV equipped with m manipulators that each of them has N degrees of freedom. In addition to the effects of mobile base, the various hydrodynamic forces exerted on these systems in an underwater environment are also incorporated into the simulation. The effects modeled in this work are added mass, viscous drag, fluid acceleration, and buoyancy forces. For drag forces, the emphasis here is on the modeling of the pressure drag. Recent advances in underwater position and velocity sensing enable real-time centimeter-precision position measurements of underwater vehicles. With these advances in position sensing, our ability to precisely control the hovering and low-speed trajectory of an underwater vehicle is limited principally by our understanding of the vehicle’s dynamics and dynamics of the bladed thrusters commonly used to actuate dynamically-positioned marine vehicles. So the dynamics of thrusters, are developed, and an appropriate mapping matrix dependent on the position and orientation of the thrusters on the vehicle, is used to calculate resultant forces and moments of the thrusters on the center of gravity of the vehicle. It should be noted that hull-propeller and propeller-propeller interactions are considered in the modeling too. Finally the results of the simulations, for an underwater vehicle equipped with one 2 DOFs manipulator, are presented and discussed in details.
Risk Analysis of the Disaster Prevention Design Criteria for a Estuarine City: Shanghai
Authors: Liu Defu , Ma Li , Jing Kun
Published: January 2009

This paper proposes a method to estimate the hydrological disaster prevention design criteria for the estuarine city Shanghai, the biggest estuarine city in China. Considering the combined effect of Typhoon storm surge, flood peak from upper river Yangtze and astronomical spring tide, the Poisson-Gumbel Mixed Compound Extreme Distribution is adopted to predict the joint probability of storm surge and flood in the condition of spring tide. The stochastic simulation technique based on the Importance Sampling Procedure is also used to predict joint probability of storm surge, flood and spring tide. In comparison with the traditional method both of them give more reasonable design criteria for coastal defence of Shanghai.
Wave Amplification and Possible Deck Impact on Gravity Based Structure in 10-4 Probability Extreme Crest Heights
Authors: Stansberg Carl Trygve , Baarholm Rolf , Fokk Terje , Gudmestad Ove T. , Haver Sverre
Published: January 2009

Model tests with a Gravity-Based Structure (GBS) platform in extreme waves are presented. First, the background for the experiments is given, based on the analysis of a possible late life production scenario in the Statfjord field. The statistical approach applied in the specification of the wave conditions, and the laboratory reproduction is then described. This is focused on the generation of a statistical ensemble of 50 extreme crests sampled from random wave realisations. The model test set-up and instrumentation is described. Finally, results on deck impact loads and nonlinear wave amplification effects are presented and discussed.
Finite Element Residual Stress Analysis Applied to Offshore Studless Chain Links
Authors: Pacheco Pedro M. Calas Lopes , Kenedi Paulo Pedro , Jorge Jorge Carlos Ferreira , Savi Marcelo Amorim , dos Santos Hugo Gama
Published: January 2009

The increasing expansion of deepwater petroleum activities has resulted in new challenges to the design of mooring systems. The complex mooring systems load history, which consists in a combination of wind, waves and currents, could induce nucleation and propagation of cracks in mooring line components. The failure of a single element in a mooring line of an offshore oil exploitation platform can produce incalculable environment damage as well as human and material losses. Offshore mooring line components like chain links must be submitted to a mandatory proof test, dictated by offshore standards, where loads higher than operational loads are applied to the mechanical component, resulting in high levels of residual stresses. Nevertheless, its presence is not considered in traditional design methodologies. Therefore, it is fundamental to develop new and more precise methodologies for assessing the structural integrity of mooring components. In this article, a comparative study is developed considering different approaches: two bidimensional finite element models, two tridimensional finite element models and an analytic model. These analyses establish the drawbacks and goals of using simpler models in the prediction of studless chain links stress distributions and in their fatigue lives. The four finite element models consider large displacements, plasticity and contact phenomena. Moreover, a simple fatigue life analysis is presented, based on SN curve, considering the effect of residual stresses in studless chain links before operation, that is, with loads caused by the proof test.