bluuebunny/crossref_metadata_2025_split huggingface dataset:
Installing Disconnectable Turrets and Offloading Buoys
Authors: Green Brian Kevin , McClure Keith 
Published: October 2008

Abstract
Cost and time pressures on installation and field operation, and health and safety concerns are encouraging new methods of subsea connection that reduce the cost and complexity of pile and buoy installation, yet also provide on-going operational benefits. This paper reports on how installing disconnectable turrets and offloading buoys is made quicker and easier, using subsea mooring connectors based on ball and taper technology, within the primary mooring lines.
The use of FPSOs with STP (disconnectable submersible turret production) or BTL (bulk turret loading) buoys has created a demanding environment for chain and shackle installations resulting in increased time, equipment and vessel costs. Subsea mooring connectors enable installation of piles without the need to use large vessels and no requirement for diving operations, resulting in a safer operation. Mooring pile installation and mooring line installation can be carried out in different campaigns and from different vessels.
Subsea connectors reduce the number and size of tugs required to facilitate hook-up of STP and BTL buoys; tugs with minimal bollard pull are used to manoeuvre the buoy to facilitate hook-up of the last mooring lines. No diver intervention is required to carry out the subsea connections. Safety concerns that arise from making up connections on the back deck of installation vessels are avoided. Moreover, disconnectable turrets and offloading buoys can be installed later in the project cycle; and with simpler mooring line arrangements, thus avoiding damage to other structures in the field and the environment such as coral reefs, during tow out.
In a recent development, subsea connectors featuring an on-board CCTV have been used to remotely find and connect a mid water arch buoy, providing easy retrieval without the need to search for a floating rope, ROVs and diver intervention. The connector systems allow an operator to abandon turrets in the event of tropical storms or temporary abandonment, retrieving them later once the vessel is back on location.
The paper will also touch on the implications of subsea mooring connectors on subsea field architecture with particular reference to the more efficient installation of Mid Water Arch Buoys.

Introduction
Installing disconnectable turrets and offloading buoys has traditionally relied on chain and shackles methods of mooring. However this approach can be costly in terms of the numbers and types of vessels needed for pile installation and buoy tow-out and connection. In addition the surface connection of the chains under-tension, can pose a significant health and safety hazard.
Analytical Determination of Ship Motions and Mooring Forces
Authors: Bomze Herman 
Published: October 2008

ABSTRACT
This paper describes a computer program which calculates the three translator motions heave, surge and sway - and the three rotary motions - roll, pitch and yaw - of a ship, represented by a rectangular block, moored in regular waves of given height and period approaching from an arbitrary direction. Accelerations, velocities and displacements and the forces in up to 30 non-linear mooring lines or breasting dolphins are printed out at successive small time intervals during passage of the waves, using first order linear wave theory and the Froude-Krylov hypothesis. The ship is represented as a rectangular block of equivalent displacement and is partitioned into a number of elements by equally-spaced planes parallel to its length, width and height dimensions. The Froude-Krylov hypothesis and the Airy Theory are used to calculate inertia, pressure and drag forces. The six degrees of freedom of the floating rigid body are represented by a system of six equations of motion which take into account all the forces acting on the body at a given instant, including hydrodynamic forces, forces in the moorings and external forces due to tornado, wind or current. A solution for the simultaneous accelerations in the six degrees of freedom is obtained by Newmark's "beta" method, from which velocities, displacements and mooring forces follow directly. The latest set of mooring forces is used to recalculate the accelerations until convergence is obtained to a predetermined tolerance, usually after only a few cycles.

INTRODUCTION
From the time man first went to sea in ships, naval architects have been concerned with the motions of a ship in a seaway. Their concern stemmed from considerations of safety of the vessel and its cargo, speed, passenger comfort and economy of propulsive power. Only relatively recently has the civil engineer become interested in the problem of ship motions. His concern was aroused by the need to locate ship berths in ever increasing water depth which brought with it increased exposure to ocean. waves. Although the design of mooring facilities tends to be governed by berthing impacts, exposed locations require that the designer also examine the forces on the ship and on the mooring structures induced by waves which may arrive while the ship is still moored at its berth rather than underway in the relative safety of the open sea.
The interaction between the flow of water around a floating body and the motions of that body is so complex that in the past greater reliance had to be placed on model tests rather than on mathematical analysis. While confirming model tests will continue to be required, the mathematics for the solution of the ship motion and mooring forces problem has made sufficient progress to provide a reasonable basis for the design or mooring facilities.
Wilson (1959) showed that a fairly accurate solution for ship motions in a monochromatic head or beam sea could be obtained by making assumptions which simplify the problem considerably.
On the Structural Design of Tubular Joints
Authors: Visser W. 
Published: October 2008

ABSTRACT
Stresses in thin-walled tubular joints can be calculated with finite-element computer programs that employ 'thin-shell' elements. Such a program, designated SATE, has been developed specifically with the object of determining stress distributions in complex tubular joints as generally encountered in the offshore industry. The program has been applied t()_ several joint geometries and good agreement has been observed between experimental and calculated results. The program thus provides insight into the structural design of tubular joints.
Using the SATE program, the influence of changes in design of both unstuffy and stiffened tubular joints on the stress-concentration factor has been studied. In this context the current API recommendations for simple tubular joint design are discussed. Calculations have demonstrated that in the design of large tubular joints allowance should be made for membrane action rather than for bending of the chord and brace walls. Such an approach leads to joints of low stress concentration.

1. INTRODUCTION
The stress analysis problem of tubular joints in offshore structures has been studied extensively, both experimentally and analytically over the past ten- yearsl. Owing to the complexity of this problem it is still far from being solved. The stress concentration of a joint is a measure of its strength in particular its fatigue strength. Here, the application of the finite-element (f. e.) method for calculating the stress concentration in such linear elastic, thin-walled structures is becoming more and more common practice. Under the assumptions of the thin-shell theory2, the f. e. method indeed suits the purpose of tackling, at least in principle, the wide range of problems related to the connections between flat plates, cylinders and other structural components.
The SATE (§structural Analysis using Ihin-shel finite Elements) program has been developed specifically for determining stresses in complex tubular joints as generally encountered in the offshore industry. The program employs an element as described in ref. 3 following ideas of Herrmann4. In comparison with the Clough-element5, the incorporation of this element in a program is more complicated, but with the same number of unknowns more accurate stresses can be calculated. In the development of the SATE-program a considerable effort has been spent on making the program flexible and economical for both unsatisfied and stiffened tubular joints. The cost involved in solving a tubular joint problem are made up of the combination of input preparation and running of the computer. It would seem that high flexibility and minimum of input preparation are conflicting criteria, as long as the problem of writing a most efficient, general-purpose mesh generator has not been solved. Grete?s progratn6 is a first step in this direction. Some aspects of the SATE program are dealt with in section 2.
Applications of an Offset Floating Breakwater Configuration
Authors: Dailey James E. , Moore Walter L. , Sethness E. Douglas 
Published: October 2008

Abstract
Laboratory tests performed at The University_ of Texas at Austin have shown that a floating offset breakwater configuration can achieve wave transmission coefficients less than 0.2 in both regular and wind waves. The offset configuration consists of vertical reflecting surfaces separated by a distance which is one-half the wave length of incident design waves.
Experiments indicate that the offset break- water provides effective wave attenuation for angles of incidence up to 45 degrees. Therefore, many applications to wave-protection in confused seas are possible. Portability of the floating breakwater permits field adjustment to give the best results. Temporary protection can be provided to construction sites where offshore facilities may be fabricated or installed. Also, the offset configuration can be built into booms for oil slick collection and confinement in heavy seas.
Good motion characterize-tics of the offset configuration encourage many applications to floating structures. A model circular structure for possible use as an offshore supertanker terminal has been tested in the laboratory. An offset configuration is suggested for pipeline lay barges to reduce their down time in rough weather, particularly beam seas.

Introduction
Protection of coastal areas from wave action is commonly achieved by building massive rubble mound structures which are supported by the soil on the bottom. Properly designed, these structures can be effective and permanent, with relatively little maintenance expense. In deep water, however, the first cost becomes very high, inasmuch as the volume of material required increases roughly as the square of water depth.
To provide more economical wave protection in deep water areas, recent interest has focused on floating structures which could be fabricated at inshore locations and towed to the application site. Cost savings result from reduced material requirements and cons traction economies in sheltered areas. Floating structures also have the advantage of portability; they can be moved from one location to another as the need arises. Their main disadvantage is that sizeable mooring forces are often required to hold them in place. These forces may exceed the working capacity of mooring lines or the holding power of anchors, possibly causing a failure in the mooring system. Such a failure could result in heavy damage to or abstraction of the structure.
The offset configuration has been designed with the objective of reducing anchoring force a which are required to hold the floating breakwater in place. Reducing the anchoring forces also implies less structural motion and less wave transmission by wave regeneration. The offset breakwater design has been tested in both regular and wind waves, and it has an even effective in attenuating the heights of both types of waves. Laboratory tests are being continued to obtain experimental misstatements of anchoring force
The Replacement of a Major Brace on MGS Platform A,Submerged Structural COOK Inlet, Alaska
Authors: Hull T.L. 
Published: October 2008

ABSTRACT
This paper describes the replacement of an underwater brace which had been torn from MGS Platform A in Cook Inlet, Alaska. The damage apparently occurred during abnormal winter ice conditions and was detected during a subsequent underwater inspection of the platform. The replacement operation, consisting of the underwater placement and structural attachment of a six foot diameter, sixty-five foot long brace between the platform legs, was conducted in an environment where thirty foot tides and twelve fps currents are not unusual. Diver operations are normally possible only during twenty minute slack tide periods that occur every six hours. Diver"activities are further hampered by the lack of visibility resulting from a heavy sediment load in the swift currents and low water temperatures.
A bolted connection, reinforced with grout, was used to attach the replacement brace to the structure. The extensive underwater work included: trimming the remaining stubs of the original brace to expose the undamaged vertical gusset plates, placing the brace and providing a temporary attachment, drilling twenty-four 1-1/2 inch bolt holes in each of the gusset plates, installation of bolts, sealing the gap between the replacement brace and the trimmed stubs of the original brace, placing reinforcing bars across each joint and grouting the connections. Most diver activities could be conducted from inside the replacement brace, independently of the tidal current, by providing access tubes at either end of the replacement brace for diver communication with the surface.
The brace was replaced within one hundred days after the damage was detected at a cost of about $500,000. Installation was completed in three weeks.

INTRODUCTION
Cook Inlet is a tidal estuary on the southern coast of Alaska. Middle Ground Shoal Platform A, owned by the Shell/Arco/Socal group, is the first drilling/production platform installed in Cook Inlet, Alaska. The platform site, Figure 1, is between the East and West Forelands in about ninety feet water depth and is exposed to severe tidal ranges up to about thirty feet. Swift tiday currents, particularly through the constriction caused by the Forelands, are normal and can exceed seven knots.' The current abates only during short slack tide periods which occur about every six hours as the tidal flow reverses. This period of relatively still flow averages about twenty minutes.
During winter months the Inlet is' covered with ice which may exceed several feet in thickness. 2 Ice stamukhi, tens of feet in thickness,3 can be formed as layers of ice are frozen together on the beaches and subsequently broken loose by receding high tides. The ice, driven by the tidal current, applies considerable force to the Inlet platforms and represents the major design load.
New Radioelectric Pi Lot Aid For Harbor Entrance
Authors: Laurent Pierre 
Published: October 2008

A new oil terminal is being built at ANTIFER, north of Le Havre. This harbour is intended to accomodate ships up to 300,000 tons. It has been found necessary to equip this harbour with a modern system allowing ships to be guided with a great accuracy, from the entrance of the channel to their berth.
An original guidance system has been developed. It is mainly composed of a radiolocation device, of a position data processing center for the generation of the parameters required for the pilot, and of a light portable equipment allowing a convenient display of these parameters.
The flexibility of the techniques used to answer the particular requirements of the ANTIFER terminal makes possible their adaptation to the numerous cases of harbour entrance areas.

CONNING SYSTEM FOR HARBOUR ENTRANCE CHANNELS

Introduction
The solution of the problem set by the guidance of ships in harbour entrance channels obliges to inform permanently the pilot of the Tnstantaneous value of. Some parameters as well as their sign and their evolution tendency.
It is therefore necessary, during the whole trip of the ship from her approach at the entrance of the channel towards her berthing, or vice versa, to select the necessary data, and to process them in real time so as to determine the parameters. These parameters are then retransmitted to the ship and displayed for use to the pilot in a direct and convenient form.
The system has to be prevented from any risk of error or misfunctioning; it has to be equipped in particular with self-testing devices and tests processes ready to be operated at any time.
Such a system is under way of realization for the French harbour of ANTIFER near Le Havre.

I.ANTIFER HARBOUR
ANTIFER harbour, a new oil terminal located at about 20 kilometres northwards of Le Havre, is mainly intended to harbour ships up to 300,000 tons.
Figure 1 shows the scheme of the portuary facilities, of the access channel with the waiting zone.
Material Properties of Submarine Mississippi Delta Sediments Under Simulated Wave Loadings
Authors: Esrig Melvin I. , Ladd Richard S. , Bea Robert G. 
Published: October 2008

ABSTRACT
Specimens of Mississippi delta sediments were subjected to simulated wave loadings in triaxial testing equipment. About 100 stress cycles of a sinusoidal form were applied under undrained conditions at about 3 cycles per minute.
Decreases in the normalized modulus (modulus Es/undrained shear strength Su) with changes in normalized stress excursion (applied excursion g/stress at failure gf) and number of cycles gf loading are shown and quantified. The applicability and limitations of these data to the analysis of submarine slope stability is discussed and recommendations for future studies are provided.

INTRODUCTION
Submarine landslides, which have severely damaged several offshore structures (1) in portions of the Mississippi delta, are known to have occurred in areas where the average inclination of the underwater ground surface is as flat as 1:125 (about 1/2 degree). The application to this problem of concepts of-soil mechanics that do not consider the interaction of the soil and the fluid above the sliding mass have never been able to provide a convincing explanation for the cause of these landslides. (2) Rational explanations have been provided when the response of the submarine soils to the hydrodynamic pressures produced by storm waves were considered in the analyses.(3) Storm waves apply transient pressures to the sea floor which, at a given point, may be considered as varying approximately sinusoidally in time. The frequencies of the long waves during major storms may reach 3 to 6 cycles per minute and the repeated, cyclic stress, applied by these waves to the sea bottom may continue for several hours. An understanding of the response of submarine soils (i.e., their variations in modulus and strength) as a result of these transient pressures is needed for inclusion in stability and deformation analyses.
Deterioration of soil strength and other physical properties as a result of repeated loading is a phenomenon which is considered routinely in earthquake analyses, vehicle mobility analyses and now in the analysis of submarine landslide potential. Presented in this paper are some of the results of a laboratory study using triaxial testing equipment of the response of Mississippi delta sediments to sinusoidally varying cyclic loadings of 3 cycles per minute. Alterations in soil modulus with increasing cycles of stressing and increases in cumulative strain during testing are reported and are related to alterations in soil strength. The data have been " normalized" to permit generalization and use in finite element and other models.

MATERIALS AND TEST PROCEDURES
The material used in this investigation was recovered in 300 to 400 ft of water as " undisturbed" tube samples from the landslide area in South Pass Block 70. Three zones are identified withinthe soil profile; Zone I is termed the " crust" zone; Zone II the " slide" zone, and Zone III the " deformed" zone.
Analysis of Simulataneous Wave Force and Water Particle Velocity Measurements
Authors: Kim Young Yuel , Hibbard H.C. 
Published: October 2008

ABSTRACT
A constant drag coefficient of 0.61 was calculated over a Reynolds number range of 2×105 to 8×105 from simultaneous measurements of-wave-induced velocities and forces. The average inertia coefficient was 1. 20. The constant drag coefficient found for a Reynolds number as low as 2×105 allows a simulation of design wave force with a smaller scale space frame structure.
The drag (inertia) coefficients were determined from drag (inertia11y) dominant portions of individual wave cycles. The measured wave force power spectrum agrees well with that calculated from measured velocities with average drag and inertia coefficients.

INTRODUCTION
The objective of this study was to establish the feasibility of measuring wave forces on a small-scale structure that could be scaled up to typical design loads on a conventional jacket-type offshore platform. It is essential to show that a supercritical flow condition (typified by constant drag coefficient) occurs over the entire structure to make such scaling possible. It is not possible, however, with existing wave-force data to show at what Reynolds number this supercritica1 condition begins, because the water-particle velocity must be inferred from the surface wave elevation. By measuring both the wave force and the particle velocity, one can remove the uncertainty due to wave theory and possible steady ocean currents affecting the calculated drag coefficient.
When unambiguous data that can be scaled up to typical design loads are obtained from a smaller scale test structure, they can be used to calibrate present-day design wave-force calculations [4]. Currently used design force calculations for a space-frame structure are based on wave-force measurements on a single pile, typically the wave-force data collected by Chevron during Hurricane Carla [2,3,9]. Design waves are assumed to be smooth and long crested (two-dimensional). Actual waves, however, are neither. The spatial distribution of particle velocities calculated for idealized design waves can be different from those for real, random waves. For the same average velocities, the drag forces on structural members are subject to random variation due to turbulence. The net result of these effects can be randomly varying force vectors over the space of a structure. Because of the changing directions of force vectors, not all of the wave forces are additive. The actual structural load in real waves may be different from when the forces are assumed in the same direction over the entire structural space, as in present design wave-force calculations.

Scaling Wave Forces
In order to simulate one physical system with another of different size, the two systems are required to be geometrically similar. In addition to geometrical similarity, certain dimensionless physical parameters must be preserved so that the experimental results of one system can be applied to another. Such parameters can be found by dimensional analysis of the governing equations for the physical system under consideration.