bluuebunny/crossref_metadata_2025_split huggingface dataset:
Special Offshore Piledriving Test
Authors: de Sitter Wolter R. 
Published: October 2008

ABSTRACT
Predictions of the bearing capacity of foundation piles generally are based upon soils investigations on site and in the laboratory. In addition, load tests on completed piles have been performed. These provide the checks on prediction methods and experimental validation of established design methods. Actual load tests on large offshore piles however, are very few and tests on piles with bearing capacities of 20 to 40 MN (4.500 to 9.000 kips) would lead to prohibitive costs. Hence an increasing importance is attached to the significance of the Soil Resistance during Driving (SRD) as a yardstick for - or at least a check on - the ultimate static bearing capacity. The SRD may be determined by dynamic measurement of strains and accelerations in the pile and also by post-analysis of blow-counts. On a test site in the Netherlands a 84" O.D. batter pile (6:1) was driven by a Hydroblok type HBM 4000 hammer to 70 m penetration. The pile was instrumented to determine SRD. Accelerations were determined by a new strain difference technique as an alternative to conventional accelerometers. An extensive soils investigation on site and in the laboratory was included in the test program.
Post-analysis of blow-count lead to values close to the static bearing capacity at successive levels predicted according to the Cone Penetration Test (CPT)-method. The SRD obtained by measurements proved to be a lower bound for the predicted static bearing capacity (80%).
Offshore field evidence from the driving of anchor piles in the Eastern Scheldt show the same correlation between SRD Obtained by post-analysis of blow counts and predicted static bearing capacity on the basis of Cone Penetration Tests, except in cases where the CPT's indicated extremely high values for cone resistance and local skin friction.

INTRODUCTION
The delivery procedure for two Hydroblok HEM 4000 hammers included an endurance driving test. The opportunity to gather information of a more general nature on the behaviour of the interaction between soil, pile and hammer generated sufficient international support of the industry, certifying authorities and scientific organisations to include soils investigations and instrumentation of the pile in the test program. In this paper some of the results and additional field evidence are presented. The methods used to obtain SRD values and static bearing capacity are summarized and discussed. Data on the test programme and additional field evidence are introduced, followed by a summary of the results and conclusions from comparisons of SRD values and predicted bearing capacities. The objective of the paper is to contribute to the development of methods to determine axial bearing capacity of piles during the actual driving process. Controlled pile-driving presents the opportunity to collect fairly accurate information on the soils during driving. The problem needing the most attention in the future is the interpretation of this information with respect to the in service behaviour of the piles during the lifetime of the construction.
A Retrospective Assessment Of Fatigue Damage Suffered By West Sole Platform W. E.
Authors: Cannell Christopher , Starsmore Neil 
Published: October 2008

ABSTRACT
In September 1978, at the end of its 12-year operational life, the platform WE was removed from the West Sole field in the North Sea for detailed examination and further research investigation.
This paper presents the results of a retrospective spectral fatigue analysis carried out on the platform, with the aim of assessing the extent of the fatigue damage incurred during its exposure to the North Sea environment.
The structural model is constructed using results from dimensional surveys, observed marine growth and actual foundation conditions. Environmental data recorded on the platform is used as a basis for wind and wave loading calculations.
Stress response spectra are calculated for eight inspection points at the end of each structural element for each sea state considered. The total damage due to all sea states is accumulated using Miner's Rule and appropriate stress concentration factors and SN-curves.
A comparison is made between the fatigue lives obtained using unidirectional data recorded on the platform and directional data obtained from other sources.
The effect on fatigue lives of some joints due to variation of some important parameters is investigated.
When completed, the study will allow an objective assessment of the viability of the latest methods used by designers to predict the fatigue lives of offshore steel structures.

INTRODUCTION
Fatigue is responsible for the failure of a great many engineering structures, and is not just a peculiarity given to offshore oil and gas production platforms. The main features of fatigue damage are:cyclic loadingtime
These can be found in a variety of engineering environments, including offshore oil platforms, which are subject to large amplitude variations in loading, due to wave action, and are usually deployed for a great length of time. Combined with a degradation of the ability of steel to withstand fatigue loads, this means that fatigue life prediction is of primary interest to the offshore designer.
For shallow water production platforms, the primary design loads are given by an extreme static load, as represented by the "design wave". This was, for example, the 100 year wave, arrived at by the extrapolation of climatic field data, and which is then applied to the structure to give the maximum horizontal shear force/overturning moment at the mud line. Any prediction of fatigue life was then based upon the design load, but scaled to fit the sea states anticipated for the service life.
The fatigue analysis was deliberately kept simple, since it was considered that during the service life of the structure the chances of failure due to overload were greater than the chances of failure due to fatigue.
North Sea structures had, to a large extent, inherited this design procedure from the Gulf of Mexico, and such was the case for the platforms deployed on BP's West Sole gas fields Indeed, platform WE was the first platform to be installed in the North Sea for the exploitation of the natural reserves.
Fatigue Strength Of Overlapping Tubular N-Joints
Authors: Ohtake Fumio , Sakamoto Suguru , Nakazato Takuzo , Minoshima Tsugio 
Published: October 2008

ABSTRACT
The main objective of this study is to obtain the quantitative guidance for the fatigue design of saddle type tubular joints with overlapping braces on the chord surface. Systematically planned sixty-one specimens were totally tested under the completely reversed sine wave axial load (R =-1). All of them were isolated N-joints with a chord of 318.5mm in outer diameter. The specimens were classified into 13 groups in accordance with the parameters D/T, d/D, T/t and g/d, where D and T are outer diameter and wall thickness of the chord, d and t are outer diameter and wall thickness of the braces and g is gap or lap length of the braces on the chord surface, and another group of joints with in-plane gusset plate reinforcement. Materials used were mild steel with the specified ultimate strength of ?u ?402 N/mm2 and high tensile strength steel with ?u ? 784 N/mm2 (equivalent of ASTM A514 Grade F steel). The cycle range repeated for each group was N = 103 ~ 2 × 106.
Characteristics of the test results were :The joints with a gusset plate reinforcement are inferior to those with a small positive gap length in the fatigue strength.By overlapping the braces on the chord surface, a fatigue life to failure of the joints is increased about 10 times as long as that of conventional gap-joints or joints with a gusset plate.The use of a high tensile strength steel in overlapping-joints has adequate effects on longevities of the joint fatigue life.

INTRODUCTION
Steel tubular structures in offshore are generally characterized by the direct welding of brace members upon the chord wall. In such connections, the stress concentration is so severe that the static and dynamic strength of the joints is much decreased. The problem is mainly caused by the matter that the axial forces of the braces directly act on the chord wall in the out-of-plane direction. In general, because the compressive and tensional forces act from the braces upon the chord wall and the sum of the vertical component forces to the chord is not so large, the joint strength is expected to be remarkably improved by direct cancellation of the vertical component forces among the braces, without passing through the chord wall.
Overlapping of the braces is one of the methods for improving the joint strength by the above effect. It is known that those joints, that is, overlapping-joints give their connections sufficient efficiencies under the statical load. The empirical formulae for the prediction of static strength of these joints have already been established on the basis of numbers of previous test results.1,2
While it is also expected that the use of these joints may increase the fatigue strength of tubular structures, enough fatigue tests for the joint have not been conducted. The researches on the fatigue strength of these joints have been deferred by the technical difficulty of the edge preparation of the braces for their complicated cutting lines.
Dynamic Analysis Models of the Tension Leg Platform
Authors: Jefferys E. Richard , Patel Minoo H. 
Published: October 2008

Abstract
Tension leg platf9rms are designed with natural periods of oscillation which are well separated from the dominant wave excitation frequencies so that displacements remain acceptably small even in severe weather conditions. However, the results presented in this paper show that the tensioned tethers can resonate at periods close to those of wave excitation if the platform is deployed in deep water where its economic advantages are held to be greatest. Analysis which ignores the tether dynamics gives good estimates of the wave induced motion amplitudes of the platform but can be seriously in error when predicting the dynamic tether stresses. An additional uncertainty is associated with interactions between the varying longitudinal tether tensions and lateral platform dynamics which can lead to a Mathieu type of instability. A simple energy balance approach is presented in this paper to quantify the effects of linear and square law damping on the severity of this instability. It is demonstrated that the effect of nonlinear square law damping is to impose an upper bound on the otherwise unstable oscillations. An algebraic expression for this upper bound is derived by consideration of an extreme 'worst case' situation.

Introduction
The use of a tensioned leg platform(TLP) as an alternative to offshore oil production from fixed or catenary moored structures is receiving serious attention within the offshore industry. Research has advanced to the stage where plans have been announced to produce oil from a north sea field using a tension leg design.
A TLP possesses a combination of desirable characteristics as an offshore work platform. The absence of a fixed rigid structure from sea surfaceto sea bed, coupled with excellent station keeping characteristics, satisfy the two important demands of economyand practicality that are made on any offshore production system. A TLP exhibits wave induced heave roll and pitch motions which are much smaller than those of a conventional floating structure. Larger off station surge and sway motions can, however, result due to the low restoring stiffnesses in these directions. This feature serves as a positive advantage since horizontal wave loads are then not fully reacted by the surface platform.
Despite these obvious advantages, the compliant nature of a TLP does raise uncertainties regarding the detailed platform dynamics particularly for deep water applications. Field and Flogeland suggest a number of problem areas which have not yet been adequately resolved. Two of these are particularly important for the TLP and are concerned with the influence of the detailed dynamics of a realistic tether system on platform motions and tether stresses and the limiting effects of fluid damping on the size and occurrence of subharmonic resonance or instabilities.
The State Of Hawaii Manganese Nodule Program:Infrastructure And Other Studies
Authors: Keith Kent M. , Jenkins Raymond W. 
Published: October 2008

Abstract
The State of Hawaii is the only local jurisdiction in the United States with a Manganese Nodule Program. The goal of the Program is to attract to Hawaii a manganese nodule processing industry which is environmentally sound, socially acceptable, and economically beneficial to the people of Hawaii.. Program elements include industry interaction, public information, and impact assessment. The infrastructure study is designed to assess industry needs, the infrastructure available in Hawaii, and gaps which may need to be filled. Two manganese nodule mining consortia have already rated Hawaii as a prime contender as a processing site.

A Brief History Of The Program
The State of Hawaii Department of Planning and Economic Development (DPED) and the University of Hawaii have been interested in manganese nodules for the past ten years. One example of early intergovernmental cooperation was the convocation of a workshop on Manganese Nodule Deposits in the Pacific, ll held in Honolulu in October 1972.1 This workshop was sponsored by the DPED, the Hawaii Institute of Geophysics, the State Marine Affairs Coordinator, and the Office of the International Decade of Ocean Exploration.
The potential of a manganese nodule industry was pointed out in Hawaii and the Sea-1974, published by the DPED.2 In that report, the Governor's Advisory Committee on Science and Technology recommended that the DPED write a report which would look at the total mining industry system, investigate and evaluate alternative processes and sites which might be used by onshore manganese nodule processing plants, and discuss plans and processes with the major mining companies.
In 1975 the Legislature provided funding to begin 'a manganese nodule program designed to assess the potential of a nodule processing industry in Hawaii. A study group of consultants from the University of Hawaii was hired and research began in March, 1977. In September, 1977, while research was in progress, a representative of Kennecott Copper Corporation visited Hawaii and at a press conference rated the Island of Hawaii as a prime contender for a processing site.3 The study group report, The Feasibility and Potential Impact of Manganese Nodule Processing in Hawaii,4 was published in February, 1978.
In the Spring of 1978, representatives of Ocean Minerals Company (OMCO) visited the State, and in September announced that OMCO would build an Equipment Test Unit (ETU) at Campbell Industrial Park on Oahu. The plant was estimated to cost $4 million, and was expected to employ a dozen people for three to five years, processing 50 dry-weight metric tons of nodules per day at an annual operating cost of $1 million. The ETU was to be smaller than a pilot plant, since it was designed only to test the processing equipment. Plans for construction of this plant have been delayed indefinitely, due to the uncertainty of the international law of the sea. In the interim, OMCO has continued to refine the processing methodology which would be tested at an ETU.
Geotechnical Analysis Of A Submarine Slump, Eureka, California
Authors: Lee Homa J. , Edwards Brian D. , Field Michael E. 
Published: October 2008

Abstract
A large submarine slump covers more than 150 km2 of a gentle (1 W) slope offshore of Eureka, Calif. We have conducted a detailed geologic and geotechnical investigation of the slump and the surrounding area to delineate the geometry of the slump, determine its cause, and quantitatively evaluate the sediment properties that led to the failure. Our study included an effort to test procedures for using short-core samples in such an evaluation. Cyclic and static triaxial and one-dimensional consolidationtests were performed on gravity-core samples from both within and outside the slump; all samples showed some degree of overconsolidation. We used a normalizedstrength- parameter approach to estimate the strength at the failure surface below the level of sampling. A stability analysis based on a pseudo static infinite-slope model shows the slump probably to be earthquake induced. This analysis also gave values of the sedimentparameters leading to failure at the slump site and to stability at surrounding sites. Owing to the complex variation in sediment properties, subtle changes in properties may determine the stability or failure of thesediment mass.

Introduction
Slumping (defined as rotational movement along a discrete failure surface) is common to many continental margins of the world and can be an important mechanism of downslope sediment transport (Cook and others, 1981). With the expanded economic exploitation of offshore areas, mass transport of sediment by slumping and other means has become an important consideration in engineering design. Because of the hazard that such mass transport poses to engineering structures, a need exists both for identification of active or potential sediment failures and for quantitative assessment of the potential formovement.
Both a geologic and geotechnical (soil mechanics) approach to the study of submarine slumps is important for complete assessment. Interpretive sub bottom acoustic profiling and side-scan sonography are required for identification of zones of past and present instability, whereas measurements of sediment strength and other characteristics are needed to diagnose failure mechanisms and stability factors. From a combined approach, an understanding of submarine mass transport can be obtained.
Studies conducted in 1977 and 1978 by the U.s. Geological Survey identified several large areas of unstable sediment, including the one discussed herein, on the continental margin off northern California (Field and others, 1980). In 1979, a combined geologicgeotechnica 1 a na lysis of a large slump a nd the surrounding sea-floor west of Eureka, Calif. was conducted. The study was designed to evaluate the geometry of the slump, the mechanism of failure, and the relative stability of adjacent areas.
Wind Overturning Effects Obtained From Wind Tunnel Tests With Various Semisubmersible Models
Authors: Bjerregaard Egon T.D. , Sorensen Erik G. 
Published: October 2008

Abstract
General trends concerning the wind overturning forces and moments on semisubmersibles are drawn from the results of wind tunnel tests carried out with a number of different semisubmersibles, each in variousloading conditions.
In (1) it was demonstrated thaL for beam wind conditions large discrepances exists between the results from empirical calculation methods as outlined in rules and regulations and results obtained from wind tunnel tests. It was assumed that lift forces were the main reason for this lack of correlation.
The present paper deals primarily with combined heel/pitch for the most cirtical wind direction close to a diagonal direction. Some typical results obtained from wind tunnel tests are presented and the importance of the lift components is demonstrated.

Introduction
IE has now become a normal practice for many designers and owners of semisubmersibles to carry out wind tunnel tests in order to obtain as exact knowledge as possible to thawind forces and moments that have to be encountered.
It is realized that the empirical calculation methods outlined in rules and regulations cannot possibly cover every conceivable layout without leading to overpessimistic .windforces for many designs. Too conservative estimates of windforces will result in a number of consequences all of which will be on the detrimental side of the cost benefit of the semisubmersible. Tne windforces are important for decisions concerning:
Anchoring systems design. Dynamic positioning strategy. Intact and damaged stability calculations. Deck load carrying capacity In the various codes of practice for calculation of wind effects it is a common method to prescribe drag coefficients in non-dimensional form for different geometrical shapes. The wind force at a given wind velocity is then proportional to the wind speed squared, the shape coefficient and the projected area. The wind moment is the product of the wind force and the arm between the centre ofaction of the wind force and the centre of reaction. This method does not include lift forces. It could be characterized as a two-dimensional way of treating the problem.
Semisubmersibles are, however, three-dimensional bodies typically with front and side areas of almost equal size, and with a large extension in the wind direction. The wind-flow over the body will therefore create a pressure distribution resulting in both a drag and a lift force. Figure 1 illustrates how this flow pattern might look, and where pressure and suction are likely to occur.
The only way of obtaining exact knowledge of the sizes of the lift and drag forces and the resulting moments is by carrying out wind tunnel testswith a carefully scaled model of the semisubmersible. During the last 2-3 years a number of wind tunnel tests have been performed with various designs for different clients at out laboratory. For this presentation some typical results and common trends concerning the wind effects have been extracted from the wind tunnel test results.