bluuebunny/crossref_metadata_2025_split huggingface dataset:
BX Flange Analysis: Significance of Gasket on Load Capability of a Subsea Connection
Authors: Chang R.T. , Fisher E.A. , Hall G. 
Published: October 2008

ABSTRACT
In this paper, the results of finite element analyses of API BX swivel flanges are presented. The interactions between the flange, the gasket, and the bolt preload are studied and illustrated. Two analytical approaches are explained, one with gasket in the model and the other without. The assumptions made in the analysis are scrutinized. Four failure criteria of a flange connection are identified and discussed for the subsea applications. Based on the comparison between the two models, the significance of gasket inclusion on the load carrying capacity is concluded. For the subsea applications, including the gasket in the analysis gives a more conservative yet realistic prediction than the model without gasket.

INTRODUCTION
Finite element analysis (FEA) has been utilized to determine the load capabilities of flange connections (Refs. 1 & 2). However, most of them were performed without a gasket being included in the FEA model. A Joint Industry Project (JIP) Study 'Swivel Flange Design Practice Development' was sponsored by eight companies and awarded to Cameron Offshore Engineering (COE). The original objective of the study was to determine the load carrying capacity of seventeen swivel flanges so that they may be implemented into the API 17D Specification. As a side-study, the effect of including the gasket in the finite e1ement mathematical model was also investigated. The reason for the side-study was the discovery that the load carrying capacity disclosed by the model with a gasket was lower than the API published data.
Four criteria selected to define the load capabilities of the swivel flanges are:the allowable stresses in the flange and hub bodies,the allowable stress in the bolt,the pressure leakage, andthe hub face separation.
The first three requirements are general for any pressure containing equipment. For subsea connections, the flange face-to-face contact must he maintained so that no seal fretting will occur due to the cyclic loading, It was also found that the load carrying capacity defined by the hub face separation criteria is the most conservative among four.
The finite element model with gasket being included is an elasto-plastic, large displacement, non-linear analysis. There are three load paths through the gasket and the flange face, It was found that the load required to seat the gasket is 40% to 60% of the bolt preload. This significantly reduces the load remaining at the flange contact face. The inclusion of the gasket in the FEA model is the source of the discrepancies between the current study and API PRAC 86-21 (Ref. 3).

TECHNICAL APPROACH TO FLANGE ANALYSIS

Traditional Flange Analysis Approach vs ABAQUS CAXA
Flange connections are axisymmetric in geometry. The makeup load, the pressure load, and the tension are all axisymmetric, only the bending moment is not, In the past, the bending moment was included in the axisysmmetric model by the equivalent tension modeling scheme, that is only valid for one sectional plane.
Sand and Gravel Resources on the Atlantic Continental Shelf: A New Look
Authors: Amato R.V. 
Published: October 2008

ABSTRACT
Sand and gravel maps of the U.S. Atlantic Continental Shelf were recently compiled at a scale of 1:1,000,000 by the Minerals Management Service. The maps cover the North, Mid-, and South Atlantic, and South Florida areas. They show deposits of sand, gravel, silt, and clay as well as differences in mineral content, from carbonate-rich sediments in the South Florida area to quartz-rich sediments north of Cape Hatteras. Sand and gravel volumes were calculated for each of the map areas and include identified and undiscovered resource categories.
The North Atlantic map area contains the greatest thicknesses of sand and gravel-most is concentrated on Georges Bank and Nantucket Shoals. Most of the deposits are of glacial origin and have an average thickness of 15 m. The North Atlantic contains about 1.6×1012m3 of sand and gravel. The area shown on the Mid-Atlantic map lies south of the maximum glacial advance and received large volumes of sand and gravel from meltwater streams. Sand covers most of the Mid-Atlantic Shelf with an average thickness of 6 m and an estimated volume of 4. 0×1011m3. Sand in the South Atlantic map area is richer in carbonate in the southward direction. The South Atlantic is estimated to have 3. 7×1011m3 of sand with an average thickness of 5 m. Sand in the South Florida offshore area is limited to the wider shelf areas from Cape Canaveral to Miami and around the Florida Keys. The sand is predominantly carbonate and averages 4 m in thickness. A volume of 6.3 × 10 10m3 of sand is estimated for this area. Total sand and gravel resources for the entire Atlantic Continnntal Shelf are estimated at 2.4×1012m3. The need for sand and gravel is expected to increase significantly in the next century as the United States rebuilds its infrastructure and onshore deposits are depleted. Offshore sand and gravel may have to be used to meet these needs.

INTRODUCTION
A series of sand and gravel maps were compiled from old and new data at a scale of 1: 1,000,000 for the U. S. Atlantic Continental Shelf 1. Unlike other sand and gravel maps, they focus on standardizing data from many sources including compilation at one scale and use of standard grain sizes and mineral content. The maps also emphasize the potential of the specific resource or deposit for commercial uses. Sand and gravel volumes were calculated from the maps and core hole data to estimate the quantities of potential aggregate available for specific geographic areas--for instance, near major metropolitan centers. The areas covered by the maps are shown in Figure 1.
The Atlantic Continental Shelf is covered by a layer of unconsolidated rock and mineral particles of varying thickness ranging in size from silt to boulders. This layer has been subdivided into geologic units based on grain size and mineral content. Grain size classes are based on the Wentworth scale.
Disturbance and Recolonization Experiment in the Abyssal South Pacific Ocean (DISeOL): An Update*
Authors: Foell E.J. , Schriever Gerd , Bluhm Hartmut , Borowski Christian , Bussau Christian , Thiel Hjalmar 
Published: October 2008

ABSTRACT
The DISCOL study involving a long-term, large-scale, disturbance-recolonization experiment in the abyssal South Pacific Ocean was devised to achieve a better understanding of the rate, sequence, and direction of benthic community re-establishment after severe anthropogenic disturbance of the seabed similar to that expected to result from deep sea floor mining. The project is funded by the German government and has been in progress since February, 1989, when the experiment was initiated during a two-month cruise aboard FS SONNE. After site selection and baseline assessments, a circular area of the seabed was impacted using a specially designed disturber device and then examined during an ini tial post-impact sampling series. The DISCOL site was sampled again during a second cruise in September, 1989, about six months after the impact was created. A third cruise of the recently rebuilt and enlarged FS SONNE will again visit the site in January-February, 1992, in order to carry out another post-impact sampling series three years after the disturbance.
Bottom sediment and biota samples, photo/video images, and other data obtained during the first two cruises are continuing to be evaluated, but some initial results have become available and are summarized in this paper. Experimental studies on large scales have rarely been attempted or successfully carried out in the challenging deep-sea milieu, but are vital to understanding biological processes and evaluating impacts resulting from ocean mining and other future industrial incursions into this largest and least understood of marine environments.

INTRODUCTION
The DISCOL (disturbance-recolonization) experiment in a manganese nodule area of the southeastern Pacific Ocean is funded by the German Federal Ministry for Research and Technology and has been in progress since February, 1989, when a circular 10.8 km2 area of the sea floor at depths near 4150 m and located approximately 650 km southeast of the Galapagos Islands (Figure 1) was selected as the for a large-scale and long-term study.1,2 The site was divided into eight pre-shaped sectors, each consisting of a central and a peripheral region separated by a 350 m wide buffer zone. Five central and five peripheral sector regions, designated according to their compass position prefixed by a C or P respectively, were randomly selected for concentrated study (sectors labelled in Figure 1). After taking a series of pre-impact baseline samples (DISCOL 1/1) to serve as controls, the DISCOL Experimental Area (DEA) was intentionally disturbed with a specially designed eight meter wide "plow harrow" device during the later part of February and in early March of 1989. 3,4 The disturber device was towed across the DEA center a total of 78 times on diametric courses which resulted in a central region of densely clustered plow tracks surrounded by a less severely affected peripheral region as shown in Figure 2.
Jackup Rig Foundation Modelling
Authors: Murff J.D. , Prins M.D. , Dean E.T.R. , James R.G. , Schofield A.N. 
Published: October 2008

Abstract
Centrifuge tests of single jack-up legs on sand seabeds have been used to improve and extend an analytical model of jack-up foundation behavior previously proposed in a joint industry study (3). These enhancements are hased on the data analyzed to date and are still undergoing development. The modified analytical model was used to predict three leg experimental behavior after the model parameters were defined. The-se-predictions compared favorably although several deficiencies were noted. Of primary importance is the observation that the three leg models exhibit significant foundation rotational fixity in both loose and dense sand. These results are most relevant to competent soils where leg penetration is shallow, such as many sites in the Central North Sea.

Introduction
An independent leg jack-up rig (ILJU) can be idealized as a portal frame as shown schematically in Figure 1. The deck is relatively rigid and the legs act as simple beam columns. Horizontal loads induce swaying of the structure with the deck responding approximately as a single degree of freedom system. As such, the jack-up response is very sensitive to the degree of rotational 'fixity' of the spud can foundation. For a given static load, the deck-leg moment, a key response variable, can vary by a factor of two depending on the foundation fixity condition. Furthermore, the natural period of the structure can also vary by a factor of two. (A stiffer foundation reduces the moment and the natural period.) A more detailed discussion of these interrelationships is given in Refs. 2, 3, and 4. For economic reasons, a jack-up is typically operated near its maximum safe water depth. Therefore, the foundation stiffness assessment often strongly impacts rig selection. This issue has been particularly important in the Central North Sea where, at the outset, water depths dictate the use of larger rigs.
The spud can fixity is, of course, highly dependent on the nature of the seabed on which it rests. The importance of the foundation behavior has motivated considerable research in recent years, for example see Refs. 2, 3, and 4. While substantial progress has been made in quantifying spud can stiffness, there remains a high level of uncertainty in this process. The study reported herein is intended to extend previous work on this topic (2, 3), and to provide a progress report on an ongoing experimental program.
This paper reports the results of extensive centrifuge model tests on spud can foundations supported on uniform sand seabeds. The test conditions were varied to include a range of sand densities (loose, medium dense, and dense), spud can shapes (flat and conical), and load paths. Both single leg and three leg models were tested. The results have been interpreted in the context of a theoretical 'macroscopic' plasticity model where the total spud can response is idealized as an elastic, work-hardening plastic element. The work-hardening parameter in this case is taken to be the penetration depth of the spud can into the soil.
Control and Dynamics During Lift Installation of the Snorre TLP Concrete Foundation Templates
Authors: Lange F.C. , Hetland Steinar , Knudsen J. 
Published: October 2008

ABSTRACT
The paper describes installation aspects of the Snorre Concrete Foundation Templates (CFT'S). The method used to bring the CFT"S to the correct penetration is described as well as the use of the SSCV DB102 to control the CFT during this part of the operation. Results from the preparatory Dynamic Analysis are discussed to indicate the dynamics in the hoist arrangement during the phase where the SSCV is "flied" to the seabed via the hoist wires and CFT. Offshore measurements were performed on the hoist forces and CFT motions. Analysis of some of these measurements are compared with the anticipated responses. It is shown that the positioning requirements and the dynamics involved in such an operation are well controlled.

INTRODUCTION
In June 1991 the Semi-submersible Crane Vessel (SSCV) DB102 lift installed four Concrete Foundation Templates (CFT"S) at the Snorre Field in the Norwegian sector of the North Sea. The installation was performed by HeereMac v.o.f. (HeMc) under subcontract to Norwegian Contractors as. (NC). The operator of the field, Saga Petroleum as. had granted NC an EPCI contract for fabrication and installation of the CFPS.
Each CI?T had a weight of around 6000 tonnes and had to be dual crane lifted and lowered to a depth of 310 meters to function as suction anchors for the Snorre Tension Leg Platform (TLP) tethers. The application of the CFT's required accurate positioning on the seabed to within 0.5 m. It was also required that the penetration in the seabed was performed with sufficient control to avoid damaging the soil structure. For this reason the SSCV was used to control the rate of lowering and the inclination of the CFT during its initial penetration. To ensure positioning within the required tolerance the CFT was guided by the SSCV until a penetration of 4 meters in the seabed was reached, after which the rigging was disconnected and the CFT was brought farther down to 12 meters penetration. The first four meters took about three and a half hours during which the SSCV was "flied" to the soil by its crane system, which very much governed the dynamic characteristics of the combined SSCV/CFT system. To avoid soil collapse in this phase it was necessary to impose relatively strict weather limitations on the installation.
The CFT Lifts showed the first use of the Display, Logging and Simulation (DLS) system installed on the SSCV during the previous winter by which hookloads and SSCV motions could be monitored and stored. The DLS system enables actual display of relevant data and (ballast) simulation of, in particular, heavy lifts to ensure a safe operation (Refer also to Reference 1). In order to monitor the CFT motion during installation the CFT'S were equipped with a temporary acceleration package. This package was capable of logging and storing the acceleration of the CFT during the whole installation sequence but was not part of the instrumentation needed for the operation.
Response of Tension Leg Platform to Wave Drift Forces
Authors: Li Tousun , Kareem Ahsan 
Published: October 2008

ABSTRACT
The wave drift forces on tension leg platforms (TLP) are contributed by second-order potential and viscous wave load effects, the fluctuations in wave surface elevation and the influence of platform displaced position on the wave excitation. These forces are expressed in terms of in-phase and out-of-phase drift forces. In this study, computationally efficient time domain and frequency domain based schemes are developed to evaluate the TLP response to drift forces. These schemes retain the statistical relationship that exists among these drift forces and the first-order wave forces which is important for the combined response analysis. A parameter study is conducted to delineate the relative significance of different drift forces for several representative sea-states.

I. INTRODUCTION
In addition to the wave forces at the typical wave frequencies in a sea-state, a compliant structure experiences slowly varying wave drift forces. These forces originate from various mechanisms involving the nonlinearity of the viscous drag term, nonlinearity in the potential forces, variations in free water surface elevation near TLP columns and the nonlinear feedback of the structural response to the wave loads. The tension leg platform has low natural frequencies in the compliant modes, i.e., motion in horizontal plane. The wave drift force at the difference frequency contributes significantly to its horizontal displacement. In view of the complexity ofloading and TLP response characteristics, an enhanced response prediction capacity with respect to the environmental loads promises to provide useful input to the reliable design of TLPs in deep water. This paper focuses on the computation of waveinduced drift forces and associatedplatform response utilizing computationally efficient schemes developed in this study.
Many researchers (e.g., de Boom et al, 1985) have described the drift forces on a TLP as a result of the second-order terms in the wave diffraction force. This force is often called potential drift force. Others (Finnigan et al., 1984 and Botelho et al .,1984, Salvensen et al., 1982) have focussed on the fact that the drag force on the TLP components can cause viscous drift force resulting from the nonlinearity in Morisonls drag force formulation. Normally the wave forces on a TLP are calculated at their undisplaced position. McIver (1976) and Rainey (1977) have emphasized that the wave effects on TLPs should be evaluated at their displaced position. In regular waves, by neglecting this effect one may underestimate response by a steady offset. In random wave conditions, this offset results in another form of drift force (Li, 1988, Li and Kareem, 1992c), which herein is called displacement feedback drift force. In this study, numerical scheme were developed, in both time and frequency domains, to describe the TLP response induced by different drift forces on TLP horizontal motion. It is noted that the total drift force is not a simple summation of the individual drift forces.
Development and First Use of the Jolliet TLWP Tendon Inspection System
Authors: Hein N.W. , Warren D.H. , Saffrhan R.W. 
Published: October 2008

Abstract
The development and installation of the Jolliet Tension Leg Well Platform (fLWP) included several innovative designs and novel equipment developments. One of these novel developments included the in-situ tendon inspection system. This system, based on the ultrasonic inspection method, was successfully developed and used offshore for the baseline inspection of the 12 TLWP tendons and length adjustment joint threads. This paper details the original design requirements, the development and field testing of the system, and the use of the system offshore in the Gulf of Mexico. Additionally, the results of the inspection, proving the value of the extra care in the on-land fabrication of the tendons, confirmed the high quality of these components since there were no reportable flaw indications detected in any of the inspected components.

Introduction
The Jolliet Field Tension Leg Well Platform (fLWP) currently holds the world's deepwater record for a petroleum production platform. 1,2 This platform is located approximately 170 miles southwest of New Orleans, Louisiana, in the Gulf of Mexico on Green Canyon Block 184. The platform is moored in a water depth of over 1760 feet.
The major system that provides for the functioning of the TLWP is the mooring system. The main components of the mooring system's 12 tendons are shown in Figure 1. Figures 2 and 3 present detail schematic drawings of the top and bottom connectors and the tendon pipe. These components are circurnferentially welded together to make up the required tow-out leg lengths of approximately 1685 feet. This leaves the top of the tendons approximately 68 feet below the water surface to the top of the tie-down porch. The 12 tendons are positioned in groups of three around each of the four corner columns. The detail design of the TLWP is discussed in Reference 3.
Previous papers have described the development of the novel tendon pipe materials and the fabrication of these tendons 4,5 The design and modelling requirements of the TLWP tendons were also previously discussed. 6 Based on this criteria, the specific requirements for the insitu tendon inspection system were described in Reference 7. A description of the preliminary tendon inspection system was presented in Reference 8.
This paper focuses on the development, onshore testing and deployment of the inspection system. The first offshore use of the system for inspecting all 12 TLWP tendons is also discussed, together with presenting actual testing results.