bluuebunny/crossref_metadata_2025 huggingface dataset:
A Reliability Based Fatigue Damage Theory for Safe Design
Authors: Nash C. D.
Published: November 2009

A reasonably safe reliability approach to a fatigue damage theory can be based on the fact that, in most cases involving the public safety, the designer can accept only very low probabilities of failure by fatigue. Thus we must be almost exclusively concerned with the lower left-hand tails of the associated distribution functions. An approach to damage theory is presented based on this concept and its possible utility reviewed. The Weibull distribution is utilized with three parameters. Suggestions are made as to needed fatigue testing.
Energy Losses due to Limit-Cycle Behavior of a Large Tanker Under Automatic Steering Control
Authors: Reid R. E. , Youhanaie M.
Published: November 2009

The problem of limit-cycle behavior of a 250,000-dwt tanker in full-load and ballast conditions under automatic steering control in calm water is addressed. The approach presented involves digital computer time domain simulation studies of the yaw-sway-surge-rudder coupled motions of the ship emanating from nonlinearities in the steering system. It is shown that the amplitude of limit cycle in yaw remains, in general, within acceptable limits for open-seas navigation for a fairly wide range of autopilot bandwidths. Propulsion losses resulting from limit-cycle behavior in calm water are shown also to be, in general, small relative to the losses experienced in some conditions in waves. It is shown, however, that whereas increasing bandwidth reduces limit-cycle behavior in calm water, it can be expected to increase propulsion losses in heavy weather. The problem this poses in. design of steering gear controls and autopilot for this type of ship is discussed.
The Trans-Alaska Pipeline System Synthetically Insulated Workpad—An Evaluation of Present Conditions
Authors: Clarke E. S. , Krzewinski T. G. , Metz M. C.
Published: November 2009

The purpose of the insulated workpad study, described in the following paper, was twofold. First, the owners of the Trans-Alaska Pipeline System (TAPS) needed an evaluation of present conditions of the insulated pad to determine the feasibility of plans by builders of the Alaska Natural Gas Transportation System (ANGTS) to reuse the TAPS workpad for parallel construction. Secondly, since the integrity of the elevated support system used by TAPS in insulated workpad areas was dependent on the insulation maintaining a shallow active layer, it was important for Alyeska (the operator of TAPS) to be assured that the insulated pad was performing as designed. The fieldwork undertaken for the study included test pitting and probing to determine the depth of thaw, sampling the insulation, and installing thermistors for long-term temperature monitoring. The insulation samples were tested for several parameters. Total performance of the workpad was better than expected, although several types of problems were encountered. Most were related to construction practices or postconstruction activity.
Energy Recovery From Refuse in the Kiel District Heating Station
Authors: Feindler K. S. , Grimm H.
Published: November 2009

The Kiel resource recovery facility proves that dependable waste disposal service can be combined with efficient energy recovery. During the first 8 yr of continuous operation, approximately 870,000 t of refuse were processed. By combusting this refuse, 1.9 million t of steam were generated for the commercial sale of district heat. Besides eliminating the need for conventional disposal by landfilling, the city avoided having to import 37 million gal of foreign oil. The facility’s key design aspects are outlined, but special emphasis is placed on the presentation and discussion of operating results. Extensive multi-year statistics are used to discuss both general and specific operating parameters. Particular consideration is given to energy conservation, environmental protection and economics.
Buckling of Risers in Tension due to Internal Pressure: Nonmovable Boundaries
Authors: Bernitsas M. M. , Kokkinis T.
Published: November 2009

Open-ended tubular columns may buckle globally as Euler columns due to the action of internal fluid pressure even while they are in tension along their entire length. Hydraulic columns, marine drilling and production risers are, therefore, prone to such static instability. This paper explains this phenomenon, defines the critical riser length for which this instability may occur and provides graphs with values of the critical length which can readily be used for design purposes. Risers with nonmovable boundaries are considered; namely, hinged-hinged, clamped-hinged, hinged-clamped and clamped-clamped risers.
Simple Models to Evaluate Dynamic Guyed Tower Response
Authors: Morrison D. G. , Will S. A.
Published: November 2009

The Guyed Tower is a system designed for use in relatively deep waters (more than 1000 ft (300m)). A model is described that mimics the response of the tower. This model calculates the response by a single degree of freedom (SDOF). The properties of the simple model are derived from stiffness, mass and hydrodynamic properties of more detailed models. The simple model is used to evaluate different mooring system configurations, and to determine the influence of dynamic mooring system properties on overall dynamic tower response.
Energy Losses Related to Automatic Steering of Ships in Waves—Part II: Performance of Controllers Designed to a New Criterion
Authors: Reid R. E. , Mears B. C. , Griffin D. E.
Published: November 2009

Minimization of energy losses associated with the steering control of modern ship types is discussed on the basis of frequency-domain sensitivity analyses and time-domain simulation studies. A high-speed containership and large tankers in the full-load condition are analyzed. A new performance criterion for minimization of steering-related propulsion losses is presented, and controllers designed to it using linear quadratic Gaussian (LQG) techniques. In the case of the containership, the resulting controller is shown to have the potential to reduce the net losses related to steering below those of the uncontrolled ship through proper use of the rudder in some conditions. While this does not seem possible for the tankers, the results indicate that a controller designed to the new criterion results in lower losses than a controller based on a form of criterion to which new autopilots for tankers are presently being designed. The implications for both autopilot and steering gear servo-design based on these results are discussed.
Rotary Drill Bit/Rock Model With Cutter Offset
Authors: Umez-Eronini E. I.
Published: November 2009

A kinematic model of a roller cone bit is developed and integrated with a rock fracture description to simulate test data from a study on the effects of bit offset. The model predicted bit tooth patterns on the rock face similar to those in the experiment. Larger cutter offsets induced increased dragging action to the motion of the bit teeth. For a given bit-rock system, volume removal also increased with bit offset up to a limiting offset value beyond which lower drilling rates were predicted.
An LPG Pipeline Break Flow Model
Authors: Morrow T. B. , Bass R. L. , Lock J. A.
Published: November 2009

An LPG pipeline break flow model has been develped to evaluate the flammability hazards associated with a pipeline rupture. The model estimates the time-dependent flow rate of LPG from a pipeline rupture, the gravity spreading of the LPG vapor layer over the ground, and the dispersion of the vapor cloud downwind of the break location. Examples of model predictions are presented to illustrate the effects of pipeline isolation valve spacing, and shutdown reaction time on the flammable cloud boundaries that could result from a partial break in a propane pipeline.
Optimized Ejector-Diffuser Design Procedure for Natural Gas Vapor Recovery
Authors: Dutton J. C. , Carroll B. F.
Published: November 2009

A procedure for designing optimized ejector-diffuser systems for recovering natural gas vapor from oil storage tanks is presented. The system utilizes high pressure gas from the separator to entrain the ambient pressure gas from the tanks and then pumps the mixture to the sales line. The analysis predicts the minimum separator pressure and the optimum nozzle Mach number and ejector area ratio required to accomplish this task. The results of a parametric study suggest that this system is feasible and that the higher the required ejector compression ratio the more critical is the use of an optimized design.
Knocking From Valve Hammer in Triplex Pumps
Authors: Collier S. L.
Published: November 2009

This paper investigates valve hammer as opposed to water hammer in triplex pumps, both of which produce knocking under certain distinctly different hydraulic operations. The occurrence of water hammer is reviewed and the development of valve hammer is discussed and documented.
Practical Applications of a Versatile Geothermal Simulator
Authors: Nixon J. F.
Published: November 2009

Since 1976, the author has programmed, developed and applied a versatile two-dimensional geothermal simulator for many interesting applications in cold regions engineering. This paper concentrates on applications to problems which have not been hitherto easily solved by other available geothermal models. Some of the important capabilities of the HAL simulator are: (i) radial or cartesian coordinate options, (ii) convective ground water flow component, (iii) simple data entry, (iv) ability to specify internal “pipes,” or areas of specified temperature, (v) monthly surface temperature and snow cover inputs as boundary conditions. The first application involves a steel pile, embedded in warm permafrost. A circular cryogenic storage tank is studied next, and the effectiveness of an insulation layer is illustrated. The convection option in the program is invoked when studying the effects of ground water flow around a series of vertical freeze pipes. Finally, the thermal degradation beneath an Arctic lake is studied, and the subsequent refreezing and growth of a pingo has been simulated.
A Computer-Based Simulation of Ice-Breaking by Impact
Authors: Mansour A. , Seireg A.
Published: November 2009

A computer simulation is developed for investigating ice-breaking by impulsive loading based on a specially developed finite element code. The computer program is capable of dealing with the multitude of complex conditions encountered in simulating ice-breaking. It is able to simulate stress, strain and axisymmetric states under different dynamic loadings such as stress waves generated by explosives, time-dependent forces and displacements, or stresses produced by impact. Moreover, the code is capable of handling different types of materials, in order to idealize the interaction between layers of ice with different properties and between ice and water. Different theories of fracture are included to facilitate the adoption of the program to the simulation of various types of ice. The simulation is utilized to develop dimensionless relationships for predicting the necessary conditions for ice-breaking by impact.
An Acoustic System for Pipeline Profile Measurement
Authors: Van Calcar H.
Published: November 2009

This paper presents an acoustic position measurement system used for precise three-dimensional flowline profile measurement. The system measures several points along the flowline using the long-baseline measurement technique and augments this measurement with depth telemetry repeaters to maintain elevation accuracy throughout the changing installation geometry. The paper discusses both the measurement system and the performance enhancement features. The paper concludes with a discussion of the hardware configuration and the accuracy that can be expected when the technique is extended into deeper operating areas.
Laminated Rubber Articulated Joint for the Deep Water Gravity Tower
Authors: Sedillot F. , Stevenson A.
Published: November 2009

The Deep Water Gravity Tower is an articulated structure resting on a fixed base through an articulated joint which is composed of curved laminated rubber pads, made from alternate layers of rubber and metallic shims. The paper first outlines the main design concept with the articulated joint. Some analysis is then provided of the response to imposed rotation and vertical load. This includes a brief description of the results of a finite element analysis. The paper then reviews the tests performed on laminated rubber during 1980 and 1981 to assess the feasibility of the articulation: fatigue tests; environmental tests (effect of sea water, temperature, pressure).
Analysis of Tubular Connections Using a Thin Cylinder Approximation—Part I
Authors: Pattillo P. D.
Published: November 2009

In the first part of this two-part study, approximate equations for determining the stress state in an interference fit connection are derived. The relations presented are based on a thin cylinder approximation and include the possibility of both elastic and plastic material behavior. Comparisons of the accuracy of the results to previous elastic and finite element analyses are presented, resulting in the conclusion that the thin cylinder model provides a useful, yet simple tool for determining bearing pressure over the majority of the engaged thread region.
Ice Action on Two Cylindrical Structures
Authors: Kato K. , Sodhi D. S.
Published: November 2009

Ice action on two cylindrical structures, located side by side, has been investigated in a small-scale experimental study to determine the interference effects on the ice forces generated during ice structure interaction. The proximity of the two structures changes the mode of ice failure, the magnitude and direction of ice forces on the individual structure, and the dominant frequency of ice force variations. Interference effects were determined by comparing the experimental results of tests at different structure spacings.
Wave-Island Interactions About Circular Artificial Islands
Authors: Niedzwecki J. M.
Published: November 2009

The behavior of waves interacting with islands has gained renewed interest with the construction of exploratory drilling islands in the Arctic. This paper focuses upon the behavior of waves incident upon axisymmetric islands characterized by circular contours which vary with water depth. The island profiles of Arthur and Pocinki, which have closed form solutions, and a single tier conical island are examined. A new dimensionless formulation of Arthur’s ray theory and an extremely accurate numerical procedure to evaluate the ray integrals are presented. It is shown that each island profile leads to a distinct wave pattern about the island. These wave patterns are presented in figures which portray the wave capture and wave breaking about circular islands. It is intended that the methodology presented be used to initially assess trends and to evaluate the need for more refined analyses.
Investigation of API 8 Round Casing Connection Performance—Part III: Sealability and Torque
Authors: Asbill W. T. , Pattillo P. D. , Rogers W. M.
Published: November 2009

The performance of the API LT&C 8 Round casing connection is investigated using 7-in.-29-lb/ft pipe size. Part I showed that the finite element method was applicable for analysis using both a threaded and an unthreaded model. Part II investigated the effects of various thread tapers and external loads on connection hoop stresses. It also evaluated maximum assembly interference based on an assumed criteria. Part III addresses connection sealability based on contact pressure. Geometric end effects are found to be significant in the unthreaded model. Sealability in the middle portion predicted by hand equations is shown to be reasonable. The threaded model shows that tension reduces sealability by disengaging thread stab flanks. Assembly forces are analyzed and, along with the test results, are used to find an equation for torque. The effects of thread taper variations, tension, and pressure on torque are shown.
Stiffness and Energy Dissipation Characteristics of Guyed Tower With Dynamic Mooring Properties
Authors: Morrison D. G.
Published: November 2009

A simple model for a complex system is presented that contains the essential properties of the guyed tower. The dynamic response to wave load of a guyed tower is represented by a single degree of freedom model. Tower response, with different wave heights and hydrodynamic coefficients, using statically and dynamically determined mooring properties were calculated for a specific tower in 1100 ft (335 m) of water. The importance of this study lies in a good modeling of the cable forces, including the hysteretic effects of line damping, and in identifying cases where the quasi-static model may fail.
Selection and Evaluation of High-Strength Steel for Hutton TLP Tension Leg Elements
Authors: Salama M. M. , Tetlow J. H.
Published: November 2009

The development of the tension leg platform (TLP) for the Hutton Field in the North Sea represents the first application of this deepwater concept. The use of vertical tension legs as the mooring system is the most novel part of the TLP design. One of the unique features of the tension legs is the use of 92.5-mm (3.64-in.) thick tubulars forged from 3 1/2 percent Ni-Cr-Mo-V high-strength steel (795 MPa (115.3 ksi) minimum yield strength) as mooring elements. Because of the importance of these elements to the survival of the TLP, the chemical composition and the steelmaking procedure were critically examined and optimized. In addition, extensive evaluation of the corrosion fatigue behavior of the steel was undertaken. This paper discusses the basis for the steel selection and specification, the results of the rigorous corrosion fatigue test program, and the assessment of the variation of properties along the length and through the thickness of full-size components. These results illustrate the suitability of the proposed high-strength steel for the mooring system application and establish confidence in both steelmaking and quality control procedures.
Dynamic Motions of Marine Pipelines on the Ocean Bottom
Authors: Healey A. J. , Seo Y. G. T.
Published: November 2009

This paper describes a dynamic model of a pipeline portion exposed to wave and current forces for the purpose of assessing on bottom stability. When an exposed span is marginally stable, and trenching not possible, some motion in the presence of an extreme wave may be tolerable. Analysis of a particular case shows that a few feet of movement would occur with a 100-yr wave. The final configuration after passage of one wave is given by the analytical model and it is predicted that a moderate residual stress would be induced. It is concluded that this kind of analysis—on a case by case basis—could be used to assess risk of pipeline damage due to storm-induced movement.
Initiation of Propagating Buckles From Local Pipeline Damages
Authors: Kyriakides S. , Babcock C. D. , Elyada D.
Published: November 2009

The paper deals with the subject of initiation of a propagating buckle in an offshore pipeline. If the external pressure is high enough, then a propagating buckle can be initiated by locally denting the pipe. Such a buckle will propagate at any pressure above the propagation pressure of the pipe. The pressure at which a local geometric imperfection transforms itself into a propagating buckle is known as the initiation pressure. This pressure depends on the geometric characteristics of the damage. The paper restricts itself to a parametric study of damages produced by point, knife and plate indentors. It is found that the geometry of these types of damages can be well represented by the ratio of minimum diameter: maximum diameter of the most damaged section.
In-Plane Ice Structure Vibration Analysis by Two-Dimensional Elastic Wave Theory
Authors: Luk C. H.
Published: November 2009

This paper presents a theoretical analysis of an in-plane ice sheet vibration problem due to a circular cylindrical structure moving in the plane of an infinite ice sheet, and computes the ice forces exerted on the structure as the motion occurs. The basic equations are derived from two-dimensional elastic wave theory for a plane stress or plane strain problem. The ice material is treated as a homogeneous, isotropic and linear elastic solid. The resulting initial and boundary value problems are described by two wave equations. One equation governs the ice motion associated with longitudinal wave propagation, and the other governs propagation of transverse waves. The equations are subject to 1) either a fixed or a frictionless boundary condition at the ice structure interface, and 2) a radiation condition at large distance from the structure to ensure the existence of only outward traveling elastic waves. The governing equations are then solved by 1) Fourier transforms, or 2) Laplace transforms, depending on the problem. Closed-form solutions are obtained in terms of Bessel functions. Plots are provided for estimating the ice added mass, the damping, and the unit function response for a circular cylindrical structure vibrating in the horizontal plane of an infinite ice sheet.
Hydrodynamic Coefficients of a Mooring Tower
Authors: Chakrabarti S. , Cotter D.
Published: November 2009

Wave tank tests have been performed on an articulated tower in order to determine the hydrodynamic coefficients associated with the tower. The tower was a uniform diameter rigid cylinder and incorporated a localized load sensing device. It was tested in three different phases: 1) fixed in regular waves, 2) mechanically oscillated in still water, and 3) free to move in the direction of regular waves. Thus, different forms of the Morison equation could be compared. The forces on the small load sensing segment were measured and the coefficients were correlated with local values of KC and Re. It is found that the data for the hydrodynamic coefficients for fixed cylinders in waves and mechanically oscillated cylinders in still water are reasonably applicable to articulated cylinders in waves.
The Motions of Adjacent Floating Structures in Oblique Waves
Authors: Kodan N.
Published: November 2009

This paper describes the theory on the effects of hydrodynamic interaction between two parallel slender structures in oblique waves. The method is based on the two-dimensional diffraction theory including the interaction effect. According to Ohkusu’s theory, the sectional interaction effects on the added mass, damping coefficient and wave exciting force are evaluated by analyzing incoming waves generated by the oscillatory motion of corresponding sections. Numerical results of the wave exciting force and moment and motions for the case of a combination of a ship and a rectangular barge are presented and compared with the results from model experiments. The comparison shows good agreement. Finally, some attention is given to the relationship between the arrangement of the two structures and responses in irregular waves.
Long-Term Analysis of Wave Climate Using Short-Term Techniques
Authors: Sanchez-Arcilla A.
Published: November 2009

This paper proposes a number of theoretical probability distributions for variables of interest when planning operations at sea. Examples of such variables are: duration of storms, duration of calms, intensity of storm peaks, etc. The theoretical distributions are obtained by means of random process theory applied to the curve of evolution of Hs (significant wave height). The model is checked with six years of wave data recorded at the north coast of Spain.
Evaluation of Structural Steel Castings for the Hutton Tension Leg Platform
Authors: Ellis N. , Salama M. M. , Beggs D. V.
Published: November 2009

The use of steel castings as major structural elements of the Hutton tension leg platform represents a relatively novel concept. In order to ensure that these castings would provide adequate service, an extensive testing program was undertaken to assess variations in chemical composition and mechanical properties of prototype castings. In addition, a rigorous acceptance procedure for production castings was developed. The results of these programs showed that steel castings possessed adequate strength and toughness. Also, a welding procedure was developed which consistently produced sound weld repair and satisfactory joints between cast and plate steel.
Analytic Determination of the Buckling Speed of Towed Slender Cylindrical Beams
Authors: Triantafyllou G. S. , Chryssostomidis C.
Published: November 2009

The buckling of submerged, towed slender cylindrical beams is investigated using analytic methods. The problem is formulated using the “slender body” approximation and conditions are sought for which the beam may be in equilibrium at a deflected position. The buckling modes are expressed in terms of generalized Airy functions, and determination of the critical towing speed for buckling is made by solving the resulting eigenvalve problem. The critical towing speed is obtained as a function of the bending stiffness, length-to-diameter ratio and hydrodynamic characteristics of the beam. It is concluded that a blunt tail-end with an increase in length-to-diameter ratio of the beam and externally imposed tension have a favorable effect on the buckling stability of the beam.
Underwater Tests on Corroded Steel Piles With the Thickness Measurement by Beam Alignment System
Authors: Singh A. , McClintock R.
Published: November 2009

An ultrasonic thickness measurement by beam alignment (TMBA) system developed by Southwest Research Institute was tested on underwater corroded steel piles at the Port Hueneme Harbor near Los Angeles, California. This ultrasonic system measures the thickness of steel piles by alignment of a focused ultrasonic transducer over a pit formed on the pile by corrosion. Tests conducted at the harbor demonstrated the ability of the system to measure the thickness of corrosion-pitted piles underwater at depths ranging from 0.3 m to 2.2 m (1 to 7 ft) below the water level. The tests also demonstrated that the system was successful in measuring the thickness of rough piles—that is, those with less corrosion—as well as pitted piles. Thus, the TMBA system is feasible as an overall approach to thickness measurement.
Requirements for a Nondestructive Inspection System for the Hutton Tension Leg Platform (TLP) Mooring System
Authors: Hein N. W. , Skilbeck F. , Herd B. P. , DeVries A. J.
Published: November 2009

The mooring system is one of the most critical and novel aspects of the Hutton tension leg platform (TLP) design. The tension lines of the TLP mooring system are subjected to severe fatigue loading conditions making the continuous assessment of their integrity an essential part of the production operation. To ensure that the mooring system is performing as designed and—more importantly—that no critical damage has been sustained, an in-situ nondestructive examination (NDE) system is being developed. The inspection system requirements to not only detect but also size possible defects in the mooring system’s heavy-walled components necessitates sophisticated ultrasonic transducers be developed. In addition, a variety of micro, mini, and supermini-computers are required to process the large amount of data required to accurately size defects in the body of the components and in the threaded connections. This paper outlines the inspection requirements for the tension legs. The various concepts considered for the in-situ inspection are also discussed. Additionally presented is the ultrasonic inspection concept being developed for this inspection system.
The Thermal and Structural Properties of a Hanna Basin Coal
Authors: Glass R. E.
Published: November 2009

In an effort to understand the cavity growth mechanisms occurring during an Underground Coal Gasification (UCG) test, a study of the thermomechanical effects has been initiated at Sandia National Laboratories. The first phase of this study has been the determination of the intrinsic thermal and structural properties of the Hanna Basin Coal that was utilized in a series of four UCG tests near the town of Hanna, Wyoming. The result of this study is a consistent set of thermal and structural properties of a Hanna Basin coal. This set has been used in a model that successfully simulated the growth of the cavity observed during the Hanna II UCG test.
Guidelines for Controlling Drill String Vibrations
Authors: Dareing D. W.
Published: November 2009

Bottom-hole assemblies control the vibration response of drill strings because they are much heavier and stiffer than drill pipe. The length of bottom-hole assemblies is also a factor and the present practice of determining drill collar length often leads to natural tuning with drill bit displacement frequencies. As a result, bottom-hole assemblies are unintentionally designed to vibrate. This paper explains the causes of severe drill string vibrations and gives guidelines for controlling them.
Cavitating and Structured Jets for Mechanical Bits to Increase Drilling Rate—Part II: Experimental Results
Authors: Johnson V. E. , Chahine G. L. , Lindenmuth W. T. , Conn A. F. , Frederick G. S. , Giacchino G. J.
Published: November 2009

Analyses of self-excited, resonating jets have been corroborated by laboratory experiments. These structured jets achieved cavitation at greater ambient pressures and showed enhanced erosivity in comparison to the nonstructured jets from conventional drill bit nozzles.
Well Test Analysis for Two-Phase Flow of Non-Newtonian Power-Law and Newtonian Fluids
Authors: Gencer C. S. , Ikoku C. U.
Published: November 2009

Analysis of injectivity and falloff test data is considered during two-phase flow of non-Newtonian and Newtonian fluids. The non-Newtonian fluids considered are power-law fluids. Two sets of relative permeability data representing preferentially water wet and oil wet systems are considered. The conditions under which saturation gradients develop are thoroughly investigated. The effects of finite radius skin region and rock compressibility on pressure response are also investigated. During two-phase flow of power-law and Newtonian fluids, saturation gradients do not develop under most practical conditions. Injectivity and falloff data can be analyzed using available techniques with appropriate definitions of dimensionless variables for two-phase flow. When saturation gradients exist, the response of this transition region is not interpretable by available methods.
An Efficient Procedure of Static Analysis of Long Ocean Mining Pipe
Authors: Tikhonov V. S. , Fisher A. S. , Zubarev V. K.
Published: November 2009

The paper develops an efficiency numerical algorithm for calculation of static characteristics of a long ocean mining pipe hanging from the ship. The algorithm is based on an asymptotic theory of ordinary differential equations, namely, on Tupchiev’s method of solution of singularly perturbed boundary-value problems. The developed algorithm is shown to be fairly universal, providing fast and highly accurate computation. Prospects of asymptotic methods for long ocean pipe motion modeling are noted. Examples are given of a pipe static analysis confirming an efficiency of the developed procedure.
Two-Dimensional Model of Coupled Heat and Moisture Transport in Frost-Heaving Soils
Authors: Guymon G. L. , Hromadka T. V. , Berg R. L.
Published: November 2009

A two-dimensional model of coupled heat and moisture flow in frost-heaving soils is developed based upon well known equations of heat and moisture flow in soils. Numerical solution is by the nodal domain integration method which includes the integrated finite difference and the Galerkin finite element methods. Solution of the phase change process is approximated by an isothermal approach and phenomenological equations are assumed for processes occurring in freezing or thawing zones. The model has been verified against experimental one-dimensional freezing soil column data and experimental two-dimensional soil thawing tank data as well as two-dimensional soil seepage data. The model has been applied to several simple but useful field problems such as roadway embankment freezing and frost heaving.
The Effects of Temperature, Stress and Salinity on the Creep of Frozen Saline Soil
Authors: Nixon M. S. , Pharr G. M.
Published: November 2009

Gravel of the Prudhoe Bay area of Alaska used in the construction of artificial islands has been examined in constant load creep experiments to determine the effects of temperature, stress, and salinity on its creep behavior in unconfined compression. Over the range of conditions studied, it is found that the creep behavior is strongly dependent on each of these variables. In addition, the ice content of the specimen, itself a strong function of temperature and salinity, is found to be an important strength-determining parameter.
The Bending of Spiral Strand and Armored Cables Close to Terminations
Authors: Raoof M. , Hobbs R. E.
Published: November 2009

The problem of the bending of a spiral strand or armored cable is addressed, with particular reference to the “free bending” situation where pulleys or other restraints are absent. The analysis, based on a study of the properties of the layers of wires which form the strand (or armor), treats the “free field” bending, remote from the termination. A parallel treatment of the situation close to a termination is summarized. In the former case, limiting values for the effective bending stiffness of the strand are presented; in the latter case an examination of the behavior of an outer layer of wires sliding (with known frictional characteristics) over an inner core has led to predictions of the strains and movements between the individual wires and the inner core (as a function of wire position in the strand) which are reported in the paper. The results offer an explanation of some experimental observations from fatigue tests on a large (39mm) strand under combined steady axial load and lateral movements causing bending adjacent to the restrained termination. In particular the observed wire failures close to the socket, not at the extreme fiber positions but at the neutral axis, can be explained in terms of the much larger slip on the interlayer contact points there.
Operational Characteristics of Electromechanical Cables
Authors: Gibson P. T.
Published: November 2009

During the past decade, there has been a proliferation of operational systems which include electromechanical (or electro-optical-mechanical) cables as vital system components. Examples of such systems include: 1) unmanned remote operated vehicles (ROVs) used for subsea exploration, inspection, recovery, or repair; 2) towed arrays or towed electronic packages used for subsea maping, exploration, or surveillance; 3) moored subsea systems used for surveillance or acquisition of environmental data; 4) tethered aerostats used for communication and surveillance; 5) data acquisition systems used in oil, gas, and geothermal wells. For each of these systems, the success of the mission is contingent upon the reliable operation of the electromechanical (EM) cable which provides the strength, power, and communications link. As the applications for EM cables have become more varied and as the operational conditions for these cables have become more demanding, there has been a corresponding increase in the sophistication of cable design and manufacturing methods. Most contemporary EM cables are highly complex machines which are designed specifically for the intended application. Unfortunately, the complexities and the operational idiosyncrasies of these cables are often misunderstood by the cable user with the result being less than optimum cable performance. As cable technology continues to advance, it becomes increasingly important that cable users devote ample engineering and monetary resources to the development of cables and cable handling systems which are required for critical applications. This paper discusses many of the operational characteristics of typical EM cables and highlights the important points which must be considered during cable design. Examples are given of how cable designs may be tailored to achieve specific performance goals in terms of cable strength, elasticity, torque and rotation characteristics, bending fatigue life, and twist tolerance. The paper also compares and contrasts the operational characteristics which are achievable with cables having metallic strength members versus cables having nonmetallic (typically Kevlar) strength members. The advantages and short-comings of these two basic classes of cables are described for various strength member configurations. A list of references is provided to assist the reader in further investigations into cable response to tension, bending, and twisting.
Hydrostatic Retesting of Existing Pipelines
Authors: Kiefner J. F. , Forte T. P.
Published: November 2009

An analytical model is presented for predicting hydrostatic retest intervals in liquid pipelines which are subjected to frequent large pressure cycles. The model utilizes pressure cycle history, hydrostatic test history, and fatigue crack growth rate data for the pipe material to calculate time to failure for the largest possible defect which could have survived a previous hydrostatic test. An example problem is described which shows the value of maximizing the margin between test pressure and operating pressure in order to achieve long time intervals between tests.
Optimum Design of Elastically Supported Gyroscopes for Ship Stabilization
Authors: Lee K.-N. , Seireg A.
Published: November 2009

The study reported in this paper deals with the development of a dynamic model for the analysis of elastically supported gyroscopic absorber systems for ship stabilization. The gryoscopes are mounted on elastically supported platforms at the fore and aft ends of the ship to minimize both the roll and pitch movements. Springs and dampers are also utilized between the gyroscope gimbal and the platform. Several design configurations of the absorber are considered. Optimal design procedures are utilized to find the system parameters for best performance in each case. The performance of the resulting optimum absorber shows that introducing the elastic spring and damper between the gimbal and platform has a significant effect on reducing the ship-roll action.
Anomalous Behavior of a Marine Gyrocompass
Authors: Reid R. E.
Published: November 2009

The kinematics of a gyrocompass configuration whereby the binnacle is pendulously mounted inside a set of gimbals, commonly installed on commercial marine vessels, is examined under vessel pitch and roll motions. The gimballing errors of this gyrocompass resulting from such motions are determined as a function of its geometry. It is shown that this design results in significantly greater errors than those resulting from the same configuration with one degree of freedom removed. This anomalous behavior is explained in terms of the compass geometry using approximate analytical techniques, the results of which compare well with experimental full-scale tests.
Control of Marine Structures
Authors: Jefferys E. R. , Mavrommatakis E.
Published: November 2009

Active control of the motion of marine structures may produce structural and operational savings over conventional passive designs. It is shown how equations of motion of typical marine structures, including those with frequency-dependent coefficients, may be rendered into a form compatible with modern controller design methods. Linear quadratic Gaussian control theory is summarized and applied to a simple example. The limitations of the theory are discussed and the effects of a force-limited actuator are quantified.
Comparisons of Theory With Model Test Data for Tensioned Buoyant Platforms
Authors: Lyons G. J. , Patel M. H.
Published: November 2009

This paper presents comparisons between the results of hydrodynamic analysis and two sets of model test data for the wave-induced motion response of tensioned buoyant platforms. The comparisons are presented with emphasis on the measured and predicted behavior of the tether elements. The two sets of data used are from (i) tests performed jointly by Heriot-Watt University and University College London at the National Maritime Institute (NMI) Ltd., and (ii) published data from tests at the Norwegian Hydrodynamics Laboratory. The hydrodynamic analysis used in the comparisons is described, together with the assumptions underlying its formulation and the manner in which the lateral dynamics of the tethers are accounted for. The analysis and test data show good agreement for surge motions although discrepancies are observed for the tether tension amplitude response at certain wave frequencies. The paper also presents detailed tether tension time histories from tests in regular long-crested waves at NMI. These data demostrate the problem of high-frequency tension oscillations (often called ringing) in tethers. Although this feature is not modeled by the hydrodynamic analysis, time history data are presented to enable interpretation of the underlying physical mechanism of this phenomenon.
A Study of Pile-Soil Interaction Behavior Under Static, Cyclic and Dynamic Lateral Loadings
Authors: Gao M. , Chin D. B. , Ma M. Y. , Sun R. G.
Published: November 2009

In this paper, the pile-soil interaction behavior of a large-sized steel pipe pile in soft silty clay along the downstream of the Yangtze River is analyzed and discussed through an in-situ experiment under lateral static, cyclic and dynamic loadings, along with the static and dynamic triaxial tests on soil samples in laboratory. In the analysis, the finite element method and other simplified methods are compared using different models of lateral soil stiffness. From the results of the tests as well as the analysis, a possible formulation of the p-y curves of the pile in soft clay under lateral loadings is suggested, and a simplified method of dynamic analysis taking into account of the pile-soil interaction is also proposed.
A Simple Model of Ice Segregation Using an Analytic Function to Model Heat and Soil-Water Flow
Authors: Hromadka T. V. , Guymon G. L.
Published: November 2009

For slowly moving freezing fronts in soil, the heat-transport equation may be approximated by the Laplacian of temperature. Consequently, potential theory may be assumed to apply and the temperature state can be approximated by an analytic function. The movement of freezing fronts may be approximated by a time-stepped solution of the phase-change problem, thus solving directly for heat flow across a freezing or thawing front. Moisture transport may approximated by using an exact solution of the moisture-transport equation assuming quasi-steady-state conditions, appropriate boundary conditions, and an exponential function relating unsaturated hydraulic conductivity (defined within the thawed zones) to pore water pressure (tension). This approach is used to develop a single model of ice segregation (frost-heave) in freezing soils. Applications to published and experimental one-dimension soil column freezing data show promising results.
Lateral and Hydraulic Pressure Characteristics of Submarine Optical Fiber Cable
Authors: Yabuta T. , Hoshino K. , Yoshizawa N.
Published: November 2009

On designing optical fiber cables, it is necessary to deal with the weakness of optical fibers, such as a small breaking elongation compared with metals and excess optical loss under both lateral and hydraulic pressure. This paper presents a structural design method for submarine optical fiber cables, based on the study of both lateral and hydraulic pressure characteristics. This paper also clarifies that a composite tension member increases the lateral and hydraulic pressure strength of the cable and can protect optical fibers from extremely large force during laying and recovery.
An Exact Solution for Pistonlike Leak-Off of Compressible Fluids
Authors: Dean R. H. , Advani S. H.
Published: November 2009

Exact solutions associated with the problem of a compressible or an incompressible fluid displacing a compressible reservoir fluid are derived. Simplified forms for the fluid leak-off coefficients, available in the literature, are deduced as special cases. Nondimensionalized expressions suitable for parameter sensitivity calculations and assumption validation are also presented.
A Review of Hydraulic Fracture Modeling—II: 3D Modeling and Vertical Growth in Layered Rock
Authors: Mendelsohn D. A.
Published: November 2009

This is Part II of a two-part paper which reviews in depth the modeling of the propagation of large hydraulic fractures in underground rock formations. Based on experimental observations reviewed in Part I the need for models of the growth of general-shaped planar hydraulic fractures has been demonstrated. Part II contains reviews of both coupled fluid/solid three-dimensional fracture models and some more basic two and three-dimensional problems in linear elastic fracture mechanics applicable to the growth of fractures in the vicinity of in-situ discontinuities (interfaces) in rock-type and/or tectonic stress. The latter is referred to as the vertical growth problem since hydraulic fractures are quite often oriented vertically with respect to horizontal layering or stratification. The state of current research in both overall modeling and basic vertical growth studies is assessed and recommendations for future research are made.
On the Fatigue Strength of Wires in Spiral Ropes
Authors: Gabriel K.
Published: November 2009

Spiral ropes of high load-bearing capacity are usually made of cold-drawn steel wires of high tensile strength. This material has been investigated by many researchers, not only to determine the mechanical properties of cold-drawn wires, but also to find out more about their stress-strain behavior under tensile loading and local three-dimensional stresses. It is now possible to determine load ranges for fatigue as a function of: surface conditions of the wire; the length of the wire; the diameter of the wire; local stresses resulting from damage to the wire surface; local stresses resulting from transverse pressure at points of contact where wires cross; friction between the wires produced by changes in stress; friction between the wires produced by changes in cable curvature; friction between wires and fittings or anchorage structures. Cables can be protected from corrosion due to environmental influences. If this is done the fatigue behavior of a twisted cable primarily depends on the addition of friction energy given to the material where strong contact forces cause three-dimensional stresses. A method of determining the fatigue strength of tension members made of cold-drawn wires is described using statistical methods, results of fatigue tests on short specimens, and precision measurements of the cold-drawn wire. It is possible to reach the material dependent fatigue limit of about 300 N/mm2 with a spiral rope by a welldone structural design and corrosion protection.
In-Line Forces on Vertical Cylinders in Deepwater Waves
Authors: Dawson T. H.
Published: November 2009

Laboratory measurements of the total in-line forces on a fixed vertical 2-in-dia cylinder in deep-water regular and random waves are given and compared with predictions from the Morison equation. Results show, for regular waves with heights ranging from 2 to 22 in. and frequencies ranging from 0.4 to 0.9 Hz that the Morison equation, with Stokes wave theory and constant drag and inertia coefficients of 1.2 and 1.8, respectively, provides good agreement with the measured maximum wave forces. The force variation over the entire wave cycle is also well represented. The linearized Morison equation, with linear wave theory and the same coefficients likewise provides close agreement with the measured rms wave forces for irregular random waves having approximate Bretschneider spectra and significant wave heights from 5 to 14 in. The success of the constant-coefficient approximation is attributed to a decreased dependence of the coefficients on dimensionless flow parameters as a result of the circular particle motions and large kinematic gradients of the deep-water waves.