bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Study on the Force of Tidal Current Acting on a Multi-Tubular-Column Structure
Authors: Arita Yukio , Fujita Hideo , Tagaya Kozo 
Published: October 2008

Abstract
The various offshore structures for wildcatting or producing oil are often moored, sit on bottom or fixed on the sea bed, as required by the type of work, in waters where they are subjected to a violent tidal current.
Also, among the contruction projects of long spanned bridges in various countries to meet the demand of the recent development of traffic net work, there are cases where the bridge must be spanned across a rapid strait. In such cases, it is often inevitable to build the bridge piers amid the rapid tidal current of the strait, taking account of the present technology and the economy.
From the point of view of performing the design, production and installation, it has been found most advantages for the offshore structure or the structure of such a long spanned bridge to employ a multi-tubular column type structure.
For designing and building the multi-tubular column structure, the extent of an external force to act on the structure must be assumed. There are many external forces such as wind force wave force, seismic force, current force and so on. In this paper the current force, which comes into question on the occasion of the installation, will be discussed.
The force of tidal current acting on a single tubular column has been studied and reported several times in the past, but no studies have ever been made on the interference in the multi-tubular-column structure. Even if there would be any one, it should have been a small model experiment in a tank and that studying the interference only between two tubular columns.
In this study, a probable 6-tubularcolumn structure was used, and the force of tidal current acting on each column was obtained.
The experiment consisted of a small model test in a tank and a large model test in waters in the Hiroshima Bay. The force of tidal current to act on an actual tubular column structure has been able to be obtained by means of these tests.
The results of this experiment may be used as calculation standards in designing and constructing an actual structure.

Model Tests

I. Models used
Large Model Fig. 1 shows the outline of the large model. The six tubular columns are built into a jacket frame. The pipe columns have smooth surface without painting. Small Model The small model is shown in Fig. 2. The model is scaled down to 1/20 in horizontal section and to 1/10 in vertical section of the large model, respectively. It is made of plastic having smooth surface.
Behavior of Tubular Gusset-Plate Joints
Authors: Bouwkamp J.G. 
Published: October 2008

ABSTRACT
The paper evaluates the stress distribution of in-plane gusset plate joints under both static and cyclic fatigue-load conditions. The potential danger of the in-plane stiffness of the gusset plate in restraining the Poisson effect in the web member sections is illustrated. Under fatigue loading, tapered gusset plate joints in which diametrically opposite regions of the web member section are restrained fail at a lower number of load cycles than non-tapered gusset plate joints. Fatigue failure has been defined as the number of alternating load cycles at which a fatigue crack propagates through the thickness of the web member wall.
It is proposed to omit a penetration of the web member walls and to use either interior or exterior gusset plates. The improvement of both the stress condition and inherent fatigue life through thick-walled web-member sections near the end of the gusset plate is emphasized. The restraint of diametrically opposite regions of the same web member should be prevented.

INTRODUCTION
The rational design of welded truss joints built from circular tubes has been complicated by the radial flexibility of the chord wall or the restraining action of stiffening elements. Both effects cause severe stress concentrations. Under increasing static loads certain joints may nevertheless perform satisfactory because of a redistribution of the load transfer after initial yielding occurs. However, in connections subjected to repeatedly fluctuating loads serious stress concentrations invariably cause a premature fatigue failure. In order to improve the life expectancy of these joints, the designer should aim at reducing these stress concentrations. Although modern finite-element computer programs are presently available to assess the design, a basic understanding of the structural behavior of the joint as influenced by the flexibility and restraining effects of the several components is a primary requirement.
To reduce stress concentrations thicker walled or ring-stiffened column members, or inter welded branch members have been introduced. Also, gusset plates in the plane of the truss have been incorporated. The latter solution permits a substantial portion of the web member loads to be transferred through the gusset plate and reduces the force transfer through the potentially critical chord member wall. The structural danger in that case is no longer related to the radial flexibility of the chord member, but instead, to the concentrated force flow between the branch-member wall and gusset plate, and the excessive in-plane rigidity of the gusset. This latter effect causes a radial restraint of the branch-member walls and introduces secondary stress concentrations in the walls near the edge of the penetrating gusset plate. While the above direct force transfer and resulting primary stress concentrations are inherent with gusset-plate joints, the secondary stress concentrations can effectively be reduced by design modifications which reduce the in-plane stiffness of the gusset plates.
Finite Element Analysis of Complex Joints
Authors: Greimann L.F. , DeHart R.C. , Blackstone W.R. , Stewart B.F. , Scales R.E. 
Published: October 2008

ABSTRACT
This paper explores the application of computerized finite element modeling techniques to the design of complex joints such as those used in semisubmersible drilling platforms. The structural complexity of such joints results in complex stress fields and a lack of suitable analytical methods has caused designers to rely heavily on intuition and simple "cook book" formulas. The advent of the computerized finite element technique fills the analytical void, but experience has shown that practical economic considerations apply certain limits here also. The joint analyst seldom has the time or money available to subdivide his finite element mesh until he has achieved convergence to the "exact solution. The purpose of this study was to develop guidelines for finite element mesh layouts which would yield stress field information adequate for the joint designer's needs.
Five typical joint designs were modeled by finite elements j three by manually laying out the mesh and two via an automatic mesh generation program recently developed at Southwest Research Institute. These finite element idealizations were analyzed using the computer program STARDYNE. The results are compared with experimental stress analyses of scale models performed at Southwest Research Institute. For the cases studied, it is concluded that the finite element method gives results which are within about 20 percent of the experimental results if the elements near cylinder intersections have an arc angle of about 15 degrees along the intersection line and a length of square root rt/2 normal to the intersection line.

INTRODUCTION
The design of the complex joints of offshore drilling rigs is a problem frequently encountered for which no simple solution is available. For example, in the case of large semisubmersible and fixed platforms in deep water, the joints are frequently stiffened with rings, gussets, bulkheads, and insert plates. This constitutes a relatively complex structure so that powerful analytical techniques must be used to produce an adequate design.
Selective reinforcement of a joint at critical regions is the objective of a typical joint design. Intuition and "cook book" methods play an important role in this process. However, too much reliance on these methods may prove dangerous. In general, most designers are well aware that, without detailed knowledge of the stress distribution in a complex joint, one may tend to stiffen an apparently weak area with a resulting increase in stresses in other areas of the joint.
Until recently the only effective means of determining stresses in a complex joint has been to place strain gages on scale models of a proposed structure and locate problem areas by a "cut-and-try" technique, an expensive procedure at best. In the last few years, however, the finite element method, coupled with the digital computer, has provided the structural analyst with a powerful and cost-effective tool to analyze these joints.
The Brunei Ship Loading System for LNG:Technology Accommodates Environment
Authors: Crowl Robert , Dowdell Thomas 
Published: October 2008

I. INTRODUCTION
It's certainly not news to anyone that a general Shortage of natural gas exists in the population centers of the world. All of the industrial countries, including the United states, the industrial countries of Europe, and especially Japan, are particularly thirsty for great volumes of natural gas. It is also no surprise to all of us that the great untapped quantities of gas are usually not found at the point of need or use. Instead, these valuable stores of energy are found in such places as the deserts of North Africa, the far North Slope of Alaska, the Islands of Southeast Asia, and deep in the heart of Australia.
Through the physics of cryogenics, it becomes feasible to gather the gas, shrink its size some 600 times by successive compression and cooling, to its liquid state at a temperature in the range of -260°F. With specially constructed super tankers, the valuable liquid can be taken to the energy-short areas of the world, returned to its gaseous form and put in the hands of the consumer, you and me. This paper presents a description of the Brunei LNG Ship Loading System, a very special solution to a problem brought about by this commercially new technique, cryogenic liquefaction of natural gas at Brunei on the Island of Borneo, and subsequent shipment of the liquid in LNG ships to Japan.
The Brunei LNG Project is a joint venture of Royal Dutch/Shell and Japan's Mitsubishi Shoij and the Brunei Government. Three Japanese terminals will receive the gas, Negishi in Yokohama, Sodeguara Chiba and Sembolu. Brunei LNG, which is the name of the joint venture, owns and operates the liquefaction plant, receiving its gas from the Brunei Shell Petroleum Company, Ltd. through offshore wells. Construction of the Brunei LNG production facility was the responsibility of the engineer/constructor team of Japan Gasoline (JGC) and Procon, Inc., a Division of Universal Oil Products (UOP). Project specifications and construction cognizance on behalf of Brunei LNG, were the responsibility of Shell Internationale Petroleum Maatschaapij (SIPM), The Hague, Holland. Subcontractor to the joint engineer/ constructor team for the LNG Ship Loading System was the Cosmodyne Division of Cordon International, Torrance, California.
Total plant output is expected to reach 5 million tons per annum in full production. The liquid will be carried to Japan in seven special LNG ships that have been contracted to be built for this project. The first ship, the GADINIA, 75,000 cubic meters capacity, has been completed and has made a number of deliveries already to Japan. Checkout of the logistics operation was made in early December 1972. The GADINIA departed Brunei December 9, 1972 to make its first delivery.
Concerns and Their Impact on Offshore Design and Operations: Were Hurricanes Ivan 2004 and Katrina and Rita 2005 100-Year Events or a Result of Moving Over a Warm Loop Current?
Authors: Schellin Thomas E. 
Published: October 2008

Abstract
The return of strong Gulf of Mexico hurricanes has resulted in a re-examination of the 100 year return periods over the Gulf oil leases. Hurricane Ivan in 2004 went through Atwater Valley, Mississippi Canyon, Viosca Knoll, and Main Pass. Hurricane Katrina in 2005 traveled across Lund, Atwater Valley, Mississippi Canyon, West Delta, South Pass, Main Pass and Breton Sound. Hurricane Rita in 2005 moved across Walker Ridge, Green Canyon, Vermilion, East Cameron, and West Cameron. Do these three devastating hurricanes change the 100 year recurrence values for these oil leases, or were they 200 or 300 year events? Are there more and stronger Gulf oil leases hurricanes over the leases closest to the warm loop current?
ESRI's ArcView Software was used to plot all of the hurricanes since 1900 which had maximum sustained winds greater than 99 knots. The area of the oil leases was defined as an area north of 25N and west of 85W. The software was lso used to find all of the tropical cyclones that have moved through the following oil leases: Atwater Valley, Mississippi Canyon, Walker Ridge, and East Cameron. The results of these plots were used to estimate the 100 year return period for each of these oil leases.
If you review the major hurricanes that have moved through the Gulf Oil leases since 1900, you will find that there have been 37 hurricanes which have caused maximum sustained winds of 100 knots or more. There have been 7 years when here was more than one major hurricane over the leases: 1909, 1915, 1916, 1975, 1985 and 2005. The highest observed maximum sustained wind over the Gulf oil leases as defined above was 165 knots during Hurricane Camille on August 17, 1969 as it tracked through Mississippi Canyon, Main Pass and Chandeleur Sound. The next highest observed maximum sustained wind of 155 knots was during Hurricane Allen on August 9, 1980 south of Alaminos Canyon and Keathley Canyon. Hurricane Katrina in 2005 and Hurricane Carla in 1961 both had maximum sustained winds of 150 knots. Hurricane Rita in 2005, Hurricane Beulah in 1967 and Hurricane Ethel in 1960 all had maximum sustained winds of 140 knots. In any year the Gulf of Mexico oil leases have a 36% chance of experiencing an intense hurricane with maximum sustained winds of 100 knots or more, since there have been 37 out of the last 104 years with hurricanes with winds of 100 knot or greater winds.
There seem to be more and stronger hurricanes over the oilleases closest to the warm loop current. The paper will give the 100 year values for maximum sustained winds based on 104 years [1900-2003] and 54 years [1950-2003] for Atwater Valley, Mississippi Canyon, Walker Ridge, and East Cameron. The author will then show how Hurricane Ivan in 2004, Hurricane Katrina in 2005 and Hurricane Rita in 2005 rate.
Underwater Imagery by Mapping Sonar
Authors: Haye Edward F. 
Published: October 2008

This will be a discussion of an instrument capable of sea floor mapping with sound waves in a similar fashion to which side looking radar maps the land with radio waves from an airplane.
The instrument used is a long range side scan sonar. One developed specifically for geologic mapping of the sea bottom. This particular instrument was developed by Institut Francais du Petrole; the French governmental petroleum research company. It is capable of producing imagery as far as 1/2 mile on each side of a fish towed behind a ship.
Figure 1 is a picture of a fish. It is 13 feet long and weighs 2000 pounds. In it are mounted transducers that emit sound and receive the echoes from the ocean floor. One pulse is emitted each second.
The frequency used is 37-1/2 kilocycles, well out of the range of petroleum seismic sources. Because a much higher frequency is used, the instrument is compatible with marine seismic techniques. The fish can be towed at speeds of up to 10 knots, although the slower speeds of seismic operations are more ideal.
Figure 2 shows the way in which sound is emitted and received. Sound is emitted in a vertical beam that is 1-1/2 degrees wide on each side of the fish. The vertical sweep can be adjusted from 10 to 30 degrees. In addition to being able to adjust the sweep angle, the look angle of the sweep can also be pointed downward or more horizontally to compensate for changes in water depths.
This particular instrument is unique among sonars in that its range is 750 meters, or approximately 1/2 mile. For geologic interpretation and mapping, the range of the sonar determines the amount of bottom that is mapped with one pass, i. e. the cost per unit area. The geologic interpretability of sonar records is a direct function of the amount of the bottom that is seen; that is its range.
Ideally, the fish is kept at a constant height above sea bottom that is, 50 meters, or 150 feet. The speed of the ship and the length of the towing cable determine the depth of the fish. By pulling the fish 150 feet above the bottom, a scan of 1500 feet of the bottom is obtained on each side, with a 1500 foot blank area beneath the fish.
The range of the instrument is sufficient to allow excellent interpretation from a traverse. Interpretational abilities are enhanced greatly by other information, such as simultaneous sparker profiles. For this reason, the side scan is almost always used in conjunction with some type of vertical profiling.
Disconnectable FPSO - Technology To Reduce Risk in GoM
Authors: Aanesland Vidar , Kaalstad Jens P. , Bech Arild , Holm Anders 
Published: October 2008

Abstract
The paper describes the Submerged Turret Production System (STP) and a state of the art disconnectable FPSO. The STP technology is well proven in the North Sea, South China Sea and other offshore arenas worldwide for both disconnectable FPSO's and for permanent mooring configuration. Lately it is being used for turret mooring of one of the worlds largest FPSOs located in Mexican waters in Gulf of Mexico on the PEMEX KuMaZa field. The FPSO is scheduled for first oil April 2007 and a short update of this project is presented.
The STP technology is built on the Submerged Turret Loading - STL technology used for Offshore Loading of Crude Oil, which is further developed for Discharge of Natural Gas and is the basis for the world's first Offshore LNG Receiving Terminal, Gulf Gateway - located in US Gulf of Mexico, Block WC 603. The paper presents this turret technology and how this technology can significantly reduce development risks in the Deep Water Fields in GoM and how it subsequently can have a positive impact on insurance premiums for the FPS/FPSO facility due to the ability to safeguard and sail away from Hurricanes.

Introduction
The ability to easily connect and disconnect a single point mooring and riser system in a safe way is attractive for a number of reasons. The most obvious reason in Gulf of Mexico is to be able to remove the vessel in case of a hurricane. The technology described, has been developed over a period of 15 years, starting in the North Sea with the STL loading system for shuttle tankers and the disconnectable STP mooring and riser system for FPSOs. Basically the technology is the same, utilizing a submerged buoy integrating riser buoy and turret in one compact module which all together is disconnected.
Resolving the K-2 Salt Structure in the Gulf of Mexico
Authors: O&apos;Brien John , Rodriguez Arnold , Sixta David , Davies Mark A. , Houghton Phillip 
Published: October 2008

Abstract
While depth imaging emerged in the 1990's as a major tool enabling subsalt exploration, imaging beneath salt bodies still remains a technically challenging task. Industry has had many major successes, but also some cases where imaging quality has been inadequate for the task at hand.
Following on the heels of the first applications of depth imaging, a number of additional technologies have been developed that provide further capabilities to image the Base of Salt and the subsalt section. These expand the toolkit available to the explorationist enabling us to image some additional salt bodies, but not necessarily all, which could not previously be imaged. Where multiple independent methods can be applied, they also provide a means of cross-checking our results and evaluating our confidence in the interpretation.
In this paper we present a case study from the K-2 subsalt field in the Gulf of Mexico where Kirchhoff Prestack Depth Migration failed to resolve the Base of Salt updip of the discovery well, leading to uncertainty in the updip extent of the field. This raises key questions about the strategy to use to appraise the field. To address this problem and to guide the appraisal drilling program we used three recently developed geophysical technologies:(a) Gravity Gradiometry,(b) Wave Equation Depth Migration, and(c) Reverse Time Migration.
We present the results provided by the three techniques to show how, in this case, they can overcome the problems encountered by Kirchhoff migration. We also show how they combine to provide a high confidence interpretation of the Base of Salt and provide direction for the appraisal drilling strategy.

K-2 Field
The K-2 Field is located in Green Canyon Block 562 in the deepwater Gulf of Mexico, some 180 miles south of New Orleans. This is a subsalt field, underlying a massive salt body with salt thickness in excess of 10,000 ft. Wells drilled to date have encountered up to 340 ft. of oil pay in Miocene age sands. Prestack depth migration has played a vital role in exploring K-2, providing excellent definition of the salt body and of the underlying sedimentary section in areas where the salt has a tabular morphology. In these areas we can image the Base of Salt, which occurs at a subsea depth of approximately 20,000 ft, and also the underlying sedimentary section down to a depth greater than 40,000 ft. This represents an outstanding subsalt imaging achievement.
While prestack depth migration has yielded some excellent imaging results, the technique is not without problems. In particular, the eastern flank of the K-2 salt has a steep face (~60°) while the salt top displays a prominent structural peak immediately west of this flank. Prestack depth migration using a Kirchhoff algorithm fails to image the Base of Salt and subsalt section in this area, resulting in an uncertainty in determining the updip extent of the K-2 Field.