bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Computer Program To Analyze Suction Effects
Authors: Christensen N.H. , Haahr Frands 
Published: October 2008

ABSTRACT
An algorithm was developed to evaluate the pull-out capacity or resistance of open-bottom or closed cylinders under water and embedded in the sea floor, with full account of suction effects. The basic mechanics are very simple, but the combinations of geometry, soil conditions and failure modes are legion.
The method provides for easy parameter studies and thus for an optimal use of the suction effects in the design of small offshore platforms, submersible CPT-rigs, suction anchors for mooring buoys, etc. It works as a small 'expert system' and needs very little computing power.

INTRODUCTION
Attempts to analyse the installation procedure and the pull-out capacities for suction piles showed so many variations that it became advantageous to use a computer.
It was first required to analyse the pulling resistance of the three hollow foundation piles, open at bottom level, of a monotower offshore platform. For these piles, shorttime vertical tension (pull-out) forces are of particular interest. These forces are generated by a ship's impact or waves and vortex shedding on the superstructure.
The methods used in the program are presently being compared with conventional small-scale model tests as well as small-scale centrifuge tests. Lately also field tests on a larger pile model are planned.
There are various failure modes both for sand and for clay. These mechanisms will be mentioned as well as the main parameters which control the magnitude of the suction effect. The capability of the program will be visualized through the analysis of two structures for which the suction effects are essential.

PROBLEM INPUT
In addition to geometry, weight and shear strengths, certain assumptions concerning the suction effects are required. Various types of analysis may be used; of these the processing of test data will not be discussed.
Geometry parameters : The geometry parameters_ are defined on Fig 1. The vertical dimensions are the water depth, the total pile height, the penetration measured on the outer side of the pile, and the height of the soil plug in- side the pile.
For the horizontal pile section the data are the total (convex) circumscribed area and pe- rimeter, and the interior area and perimeter. Basically these numbers are assumed to re- present an exterior and an interior circler i.e. 'equivalent' circles if the pile section is of another shape.
Weight parameters : The total as well as the buoyant weight of the pile proper are required. The difference between these two values would show for instance whether the construction had any empty watertight com- partments.
Also the unit weight of water, and the atmospheric pressure expressed in the chosen unit system are required if any consistent unit system Is to be allowed, or if the analysis of centrifuge model tests is of interest.
Slope Angle Studies From Multibeam Sonar Data on Three Seamounts in Central Indian Basin
Authors: Kodagali V.N. 
Published: October 2008

Abstract:
Slope angles are powerful morphometric tools. Slope angle studies in manganese nodule areas using the Multi Beam Sonar (MBS) data is useful to the mining geologist. A technique to convert depth grid generated from MBS data to slope angle values data is presented here. The slope angle grid can be used to create the slope angle map. Morphology of three seamounts from Central Indian Basin and the slope angle data on them are described. The seamounts are of the heights 1000-1200 m and occupy area up to 300 sq kms. The maximum slope angle around the seamounts is 38° with average being 10°. Over 80% of the area around the seamounts will be unmineable because of higher slope angles.

Introduction
Study of slopes and surface processes has been integral part of the geomorphological studies since the second World War. Slopes provide a basis on which by successive combination into larger units, general geomorphology of an area can be reconstructed. It is an important aspect in establishing relationship between geomorphology and other factors of environment. Just as the study of slopes forms a basis for geomorphological study on land, it can also be effectively carried out on seafloor data. Submarine geomorphology is challenging because of inability to observe things first hand 1 " However, slope angle studies on seafloor data have evoked considerable interest in the last decade. 2, 3,4,. Slope angle maps along with accurate depth contour map are essential for deep sea mining geologist to evaluate the resources and to eliminate unfavorable areas for mining. The path of the mine head has to be predetermined for which a detailed bathymetric and slope angle map of the area is a prerequisite. This study describes the technique for developing slope angle maps from the Multi beam sonar data.

Slope Angle Grid Generation
With the advent of multibeam system, the quality and the coverage of seafloor area have increased many fold. To generate a depth contour map from multibeam sonar data, the data from different survey lines is merged and a combined grid of depth values is generated. The technique developed for creating a slope angle grid from the depth values grid from HYDROSWEEP system Multibeam swath bathymetric system manufactured by M/s Krupp Atlas Elektronik, Germany (See references5,6 for technical details of the equipment) is briefly described here. The slope angle grid generated from this program can be used for preparing a slope angle map of area or slope profile across the area. The program is developed on EPR 1300 computer but with necessary modifications, it can be used on any computer. The program can also be adopted for land altitude data to create slope angle grids7
J-Tube Design for Flexible Umbilicals
Authors: Ronalds B.F. 
Published: October 2008

ABSTRACT
The design of J-tubes with one or more bends under functional loads is dictated by a single force TL, the cable tension at the bottom of the J-tube. This facilitates the analysis of J-tubes using standard beam theory or, for complex shapes, a simple computer model. J-tubes experience both pull-in and pull-out loads in practice, and the latter govern J-tube design because the force TLis maximized.

1. INTRODUCTION
Flexible umbilicals comprising power, signal and fluid lines have found increasing use offshore in the control of satellite wells and subsea isolation valves. They are frequently brought into Topsides through steel J-tubes pre-installed in the jacket. Previous papers [1] have predicted pull-in loads for single bend J-tubes, but addressed the installation of a steel flowline rather than a flexible umbilical. The load required to pull an umbilical through a multiple bend J-tube is appraised in the present work; however, the stress analysis of the J-tube itself is the primary concern. A design method is developed, critical loadings other than pull-in are identified, and an optimum J-tube support configuration is highlighted. Throughout, it is assumed that the umbilical behaves essentially as a cable. A limiting flexural stiffness for the umbilical, beyond which the approach is not applicable, is estimated.

2. J-TUBE OPERATIONS
J-tubes are subject to both pull-in and pull-out loads, as indicated in Fig. 1.
The primary function of the J-tube is to enable the umbilical to be installed by pulling it up from seabed through the J-tube. This is performed using a winch located above the J-tube, which draws a cable attached to the nose of the umbilical.
Prior to installing the umbilical, the interior of the J-tube is generally protected by a diaphragm or plug at each end. 'l'& prevents free inflow of water into the J-tube and retards corrosion. Depending on its design, the lower seal can be removed by pulling outward, or inward through the J-tube.
One form of proprietary rubber diaphragm is shown in Fig. 2. During fabrication, a messenger line is passed through the J-tube and attached to the diaphragm. In-situ, the umbilical can be connected to outer side of the diaphragm just prior to pull-in. Winching in the messenger line from Topsides first breaks the diaphragm, and then pulls in the umbilical.
Umbilical installation methods vary, depending on the Operator. Another commonly used method involves the J-tube messenger line being pulled out of the J-tube by a winch on the lay vessel. The cable is then connected to the umbilical nose on the vessel deck to enable umbilical pull-in.
A defective umbilical would be removed by pulling it out of the bottom of the J-tube. Additionally, the umbilical maybe pulled out in-service due to accidental snagging from anchors or trawling.
To summarize, the following operations should be addressed in J-tube design:umbilical pull-inbottom seal pull-in/pull-outumbilical/cable pull-out
Flanged Coupling Design for the Snorre TLP Risers
Authors: Sele A.B. , Kilebu Magne 
Published: October 2008

ABSTRACT
The flanged couplings adopted for the "Snorre" TLP risers are of a new and optimised configuration. The weight is comparable to that of a threaded coupling. So ia also the fatigue strength. The ultimate strength is equal to that of the tubular cross section of the riser joint. Make up and break out can be achieved rapidly and highly accurately with small and compact tools. In comparison threaded couplings of large diameters in particular require Iarge and cumbersome torque tools which achieve. a far lass precise prestress. It is believed that flanged couplings may provide the more optimal solution in many similar applications.

INTRODUCTION
The "Snorre" Tension Leg Platform stands in 320 meter water depth and is located in the Norwegian sector of the North Sea. It is operated by Saga Petroleum as. The design provides for 44 production risers of 9 5/S" diameter. There will also be an oil export riser of 20" diameter and a gas export riser of 10 3/4" diameter. Each riser string consists of 17 joints which are 51? long. Flangad couplings have bean provided for the couplings of the production risers in the splash zone as well as for the oil and gas export risers
The splash zone type couplings are provided in the most heavily loaded sections of the risers. The design loads are given in table 1. For the moat critical ultimate load combination the gross tubular cross section of the joint including the corrosion allowance is fully utilized. The flanges do as a consequence have an ultimate capacity in excess of that of the tubular cross section. The tubular cross section is also highly utilised in fatigue. As a consequence forged upset ends have been provided to accommodate the girth welds on the production risers and the gas export riser. On the oil export riser there are flush ends.
The compact flange concept which was adopted has also been used on shore in process pipework. In order to adapt this design concept to accommodate the design requirements laid down for the "Snorre" TLP, extensive non linear finite element analysis was performed. The general purpose non Iinaar finite element programme "Solvia" /1 / was used for this purpose.("Solvia" was previously known as "Adina".) The analytical results obtained ware verified with a comprehensive programme of full scale prototype tests which are described in more detail below.

DESCRIPTION OF FLANGES
Drawings of the flange coupling for the production riser splash zone type joints are shown in figure. The flange coupling for the gas export riser is of an identical configuration. Drawings of the oil export riser coupling are shown in figure 2. To avoid special transition joints splash zone couplings and standard couplings are of an identical design. The flange faces are carefully profiled to give the desired stress distribution after prestressing. This is described in more detail in the relevant sectional below..
Composite Riser Tubes: Defect Tolerance Assessment and Nondestructive Testing
Authors: Sparks C.P. , Odru P. , Metivaud Guy , Le Floc&apos;h Christian 
Published: October 2008

ABSTRACT
The work presented in this paper was carried out as part of a Joint Industry Program to qualify composite tubes for use as TLP production/injection risers. The program included the study of the influence of different kinds of damage on tube performance and fatigue life, the assessment of NDT methods for detecting damage and its evolution, as well as ways of predicting the ultimate performance of severely fatigue tested tubes. The following oil companies supported the program: Agip, Chevron, Conoco, Elf Aquitaine, Shell IPM, Statoil.

BACKGROUND

Initial Development
The Institut Francais du Petrole (IFP) and Aerospatiale have been developing high performance composite tubes for oil industry applications for a number of years.
Initial work concentrated on exploring the possibilities of different fibers and on finding technical solutions for details such as the tube end piece connection and internal/external liners for assuring pressure tightness. A large number of small diameter tubes were then tested in tension, pressure, bending, fatigue, ageing and abrasion.
This preliminary work led to a design consisting of a filament wound tube with a hybrid structure, comprising circumferential layers and longitudinal layers (see Fig.1), reinforced with glass fibers and carbon fibers respectively, set in an epoxy resin matrix. The end piece design (see Fig.2) consisted of a conical steel insert, fitted with steel shell pieces, to which the composite was bonded.
There are many possible applications of composite materials to the offshore oil industry (see ref.1). The initial one considered by IFP/ Aerospatiale was 4" J.D. Kill & Choke lines of drilling risers. Several such tubes were built and tested and in 1983 six 15 m long tubes were successfully tested on a drilling riser in the North Sea. Composite TLP Risers
Since 1985 IFP/ Aerospatiale have concentrated on the development of larger diameter (9r) composite tubes for applications to production/injection risers of deepwater TLPs.
Work on the composite risers of the PLTB 1000 project (see ref.2) showed the potential benefits that could be gained from the principal characteristics of composites, which included high strength and low weight, as well as their elasticity and their excellent behavior in fatigue and corrosion. These promised to allow large reductions in riser top tensions and also the elimination of tensioners, leading to economic benefits.
In 1985 IFP mounted a joint industry program (JIP No.1), supported by seven major oil companies, with the object of building samples of composite risers for TLPs and subjecting them to thorough mechanical testing. The tubes were 9" ID, with a hybrid wall structure made up of glass fiber reinforced circumferential layers (total thickness 9.57mm) and carbon fiber reinforced longitudinal layers (7.28mm thick). A cross-section of the tube is shown on Fig.3, where the layered structure of the wall can be clearly seen.
Concrete TLP's in Water Depths Beyond 3,000 ft
Authors: Hannus H.G. , Engebretsen K.B. , Børresen R.H. 
Published: October 2008

Abstract
Concrete hull TLP's are established as a viable concept for field development in water depths up to 3,000 ft. The first platform is now under construction for the norwegian Heidrun field. However, as the water depth increases, the platform natural periods tend to increase, which also will increase the tether fatigue. Is there a limit for the concrete hull?
This paper describes a large size platform for Gulf of Mexico conditions at different water depths. A comparison is made with a steel hull alternative, under identical functional requirements. In particular, the tether extreme and fatigue responses are analyzed.
The results demonstrate that concrete hull platforms are competitive also beyond 3,000 ft. High natural periods can be acceptable for the tether system provided that the platform geometry gives low excitation at roll/pitch resonance as well as low responses at higher periods.

Introduction
In the last few years, concrete has been introduced as a construction material also for floating production platforms. The concrete hull TLP has been found feasible and economically attractive in water depths up to 3,000 ft, as demonstrated by Wilson /1/ and Lokken /2/. The tether system, that moors the platform, is typically designed for extreme storm condition, which also provides adequate fatigue life (assuming appropriate component design).
As the water depth increases, the fatigue life becomes more critical, as the tether stiffness decreases and the natural periods increase. In order to reduce the response at resonance, the natural periods can be reduced by increasing the tether stiffness. This means that the tether system is no longer designed for stress, but for stiffness (steel cross sectional area) " For Gulf of Mexico conditions, a practice is about to emerge, which claims that the natural periods in heave, roll and pitch should not exceed four (4) seconds.
This paper sets about to investigate the relevance of such a limit, which may be questioned on the basis that the tether responses are a function of the platform geometry. For comparison, a concrete and a steel hull are analyzed with identical tether system.

Design Basis
The environmental conditions for this study are based on published information, the extreme conditions presented in Table 1 are taken from Brewer /3/, while the fatigue conditions, the wave scatter diagram, is taken from Kinra and Marshall /4/. Three waterdepths are considered; 3,000 ft, 4,500 ft and 6,000 ft.
The platform requirements represent a large size Gulf of Mexico field. The topside mass, including payload and deck structure, is 30,000 tons (27,216 metric tonnes). This carrying capacity is defined for 3,000 ft (914 m), as the hull geometry is kept identical for larger water depths, the deck weight has to be reduced to allow for the increased tether weight. The total riser tension is 14,000 kips (62.3 MN). The riser tension is taken as independent of water depth (assumes that buoyancy is attached in very deep waters).
Reliability Analysis of the Behavior of Dropped Objects
Authors: Colwill A.D. , Ahilan A.V. 
Published: October 2008

ABSTRACT
Dropped objects, such as drill pipe, pose a potential hazard to sub-sea structures. A program has been developed to simulate the submerged trajectory of such objects, and verified against experimental data. A study was conducted to determine the design impact velocity of dropped tubulars, to aid in the column design for a floating structure. Initially the maximum attainable velocity was determined. Subsequent multiple drop simulations produced a quadratic surface of maximum impact velocity with respect to the initial drop parameters. The lack of a consistent definition for the 'design' velocity prompted the application of reliability techniques which established a relationship between impact velocity and probability of occurence.

INTRODUCTION
Small objects such as scaffolding bars may be dropped frequently with little consequence to sub-sea structures and equipment. However, occasional drops of larger objects such as drill pipe, containers and B.O.P. stacks pose potential greater risks, due to the likelihood of significant damage resulting from their impact.
Dropped tubulars, such as drill pipe/casing are particularly prone to rotational effects of hydrodynamic loading, and can turn horizontally upon entry into the water column. This can pose a significant threat to the columns and pontoons of floating offshore units where wall thickness may be reduced, as far as is feasible, to maximise topside capacity.
A study of the trajectory and maximum velocity of dropped objects aids in the design of column and pontoon configurations for floating structures. However. designing to the maximum impact velocityderived from a combination of conservative assumptions (due to a lack of better guidance) may lead to uneconomic solutions. Analyses employing multiple simulations and reliability techniques allow a more rational approach to be adopted, producing design velocities which can be associated with an acceptable probacility of occurence.

DROPPED ELEMENT TRAJECTORY ANALYSIS
Any object dropped off a platform, from the deck or during lifting operations, will undergo three distinct phases during its passage to the seabed.Falling in air.Entry into water, body partly submerged.travel through water co1umn.
The aerodynamic effects are generally small in comparison with the gravitational force on the body, therefore attention is focused on the motions of thedropped object during b) and c). A computer program has been developed for Dropped ELement Trajectory Analysis "DELTA", and utilised for the assessment of the likely maximum horizontal velocities from dropped drill pipe/casing.
The 2-D motion of the dropped object in the global system is modelled by differential equations relating lateral, vertical and translational forces. The dropped object is discretized into 20 segments, and integrations are conducted numerically. The forces and moments, computed in a local system, are updated every time step before transformation into a global system. A full description of the theory utilised in the model is presented by Luo & Davis (1992).