Time Histories of Wave-in-Deck Loading on Jacket Decks

2006 ◽  
Author(s):  
Katrine van Raaij ◽  
Ove T. Gudmestad
Keyword(s):  
Time Variation ◽  
Structural Response ◽  
Engineering Practice ◽  
Offshore Platforms ◽  
Wave Loading ◽  
Extreme Wave ◽  
Incoming Wave ◽  
Time Histories ◽  
The Difference

Most researchers agree that wave-in-deck loading is of dynamic nature and that the dynamic effects on the structural response are important. However, there exists no engineering practice for the determination of load time histories for waves hitting the decks of fixed offshore platforms. This applies to both the time variation and the magnitude of the loading. This paper presents the main recommendations for wave-in-deck loading with reference to wave tank experiments of a model of the Statfjord A Condeep platform subjected to extreme wave loading. The recommendations for loading from these tests comprise time variation as well as magnitude. These recommendations are used as a basis to suggest a simplified method to estimate wave-in-deck loading on jacket platform decks, for which, to the difference from Condeep platforms, the wave height amplification due to the interaction between the incoming wave and the structure (Swan et al., 1997) is negligible. The resulting ‘recipe’ for wave-in-deck time histories on North Sea jacket platforms is compared to relevant results previously reported in the literature. The method is categorised as a ‘global’ approach, that is, one uses an effective deck area as opposed to a detailed deck model. The method is suggested to be applicable for analyses where a ‘rough but reasonable’ estimate for wave-in-deck loading is sufficient.

scholarly journals STRUCTURAL BEHAVIOUR OF FULLY COUPLED SPAR–MOORING SYSTEM UNDER EXTREME WAVE LOADING

2014 ◽  
Vol 19 (Supplement_1) ◽  
pp. S69-S77 ◽  
Author(s):  
A. B. M. Saiful Islam ◽  
Mohammed Jameel ◽  
Suhail Ahmad ◽  
Mohd Zamin Jumaat ◽  
V. John Kurian
Keyword(s):  
Response Time ◽  
Deep Water ◽  
Mooring Line ◽  
Mooring System ◽  
Wave Loading ◽  
Extreme Wave ◽  
Spar Platform ◽  
Mooring Lines ◽  
Time Histories ◽  
Fully Coupled

Floating spar platform has been proven to be an economical and efficient type of offshore oil and gas exploration structure in deep and ultra-deep seas. Associated nonlinearities, coupled action, damping effect and extreme sea environments may modify its structural responses. In this study, fully coupled spar–mooring system is modelled integrating mooring lines with the cylindrical spar hull. Rigid beam element simulates large cylindrical spar hull and catenary mooring lines are configured by hybrid beam elements. Nonlinear finite element analysis is performed under extreme wave loading at severe deep sea. Morison's equation has been used to calculate the wave forces. Spar responses and mooring line tensions have been evaluated. Though the maximum mooring line tensions are larger at severe sea-state, it becomes regular after one hour of wave loading. The response time histories in surge, heave, pitch and the maximum mooring tension gradually decreases even after attaining steady state. It is because of damping due to heavier and longer mooring lines in coupled spar–mooring system under deep water conditions. The relatively lesser values of response time histories in surge, heave, pitch and the maximum mooring tension under extreme wave loading shows the suitability of a spar platform for deep water harsh and uncertain environmental conditions.

An Efficient Technique for Derivation of the Kurtosis of Offshore Structural Response Due to Random Morison Wave Loading

2004 ◽  
Author(s):  
G. Najafian ◽  
R. Burrows ◽  
R. G. Tickell
Keyword(s):  
Structural Response ◽  
Computational Effort ◽  
Complex Structures ◽  
Structural Elements ◽  
Wave Loading ◽  
Structural Behaviour ◽  
Evaluation Procedures ◽  
Probabilistic Description ◽  
Non Gaussian

Nonlinear wave loading leads to non-Gaussian offshore structural response so that higher-order statistical moments, such as kurtosis, are often necessary for its probabilistic description. The existing models for determination of these moments are computationally very demanding. Consequently, the distributed wave loading on the structure is idealised by a relatively small number of nodal loads, requiring care and experience in the representation of the continuous loading on (complex) structures with many structural elements. These shortcomings are successfully overcome by an approximate approach, as described herein, offering a dramatic reduction in computational effort so that the distributed loading can be idealised more realistically by a large number of nodal loads. The effectiveness of the proposed procedures, which have arisen from a UK EPSRC-sponsored project, are demonstrated by applying them to a test structure under different environmental conditions. With these improved tools, designers can now consider incorporation of more robust and precise probabilistic analysis into their evaluation procedures for structural behaviour, without facing onerous computational effort.

Effect of Wave Loading on the Seismic Behavior of a Typical Fixed Jacket-Type Platform

2008 ◽  
Author(s):  
Z. Omrani ◽  
A. R. M. Gharabaghi ◽  
S. R. Hosseini ◽  
S. Nouri
Keyword(s):  
Seismic Behavior ◽  
Nonlinear Response ◽  
Offshore Platforms ◽  
Wave Loading ◽  
Response Characteristics ◽  
Finite Element Software ◽  
Structure Response ◽  
Wave Characteristics ◽  
Damping Characteristics ◽  
Time Histories

Design of fixed offshore platforms to resist earthquakes involves many of the same problems and issues as other onshore structures. However, there are some important differences that the most important one is the presence of seawater. It influences the mass, stiffness, damping and strength characteristics of the platform, which can have important effects on the structure response characteristics. The entrained water inside the platform elements and the water that is accelerated by the motions of the structure, have very important effects on the mass and damping characteristics of the platform. The presence of other environmental loads, particularly waves can also influence the response of these structures. In this paper, the nonlinear response of a typical jacket type platform, which has been installed in Persian Gulf, under wave and earthquake loadings are studied. The structure is modeled by ANSYS, finite element software. Time histories of different earthquake loadings are applied. Wave characteristics are based on local information. These loadings are applied separately and simultaneously. Moreover, they are applied in the same direction and different directions. The results are compared with each other and the most sever cases are extracted.

Detection of Jacket Member Severance Using Structural Instrumentation

2008 ◽  
Author(s):  
Stuart D. Killbourn
Keyword(s):  
Finite Element Modelling ◽  
Continuous Monitoring ◽  
Structural Integrity ◽  
Structural Response ◽  
Offshore Platforms ◽  
Wave Loading ◽  
Repair Work ◽  
Element Modelling ◽  
Water Line ◽  
Failure Event

Fixed-jacket offshore platforms are susceptible to damage below the water line which may be difficult to observe except by underwater inspections that can be up to several years apart. An instrumentation system installed at deck-level can be used to detect the severance of a jacket member by continuous monitoring of the structural response due to ambient wave loading. Data is presented during a brace failure event that occurred on a North-Sea platform and also for subsequent repair work. The observed changes in structural response are compared to those predicted by finite-element modelling. The ability of this method to detect jacket member failure within hours of severance is an important factor in assessing the risks to personnel as well as maintaining structural integrity. In the case of this jacket member failure, the provisions made by the platform operator meant that the incident was anticipated, planned for and ultimately managed in a way that enabled production at the platform to continue without interruption.

FRACTIONAL DETERMINATIONS OF URINARY 17-KETOSTEROIDS IN HYPEREMESIS GRAVIDARUM

1962 ◽  
Vol 41 (1) ◽  
pp. 123-128 ◽  
Author(s):  
Pentti A. Järvinen ◽  
Sykkö Pesonen ◽  
Pirkko Väänänen
Keyword(s):  
Hyperemesis Gravidarum ◽  
First Trimester ◽  
Control Group ◽  
Before And After ◽  
Daily Urine ◽  
First Trimester Of Pregnancy ◽  
The Difference

ABSTRACT The fractional determination of 17-ketosteroids in the daily urine was performed in nine cases of hyperemesis gravidarum and in four control cases, in the first trimester of pregnancy both before and after corticotrophin administration. The excretion of total 17-KS is similar in the two groups. Only in the hyperemesis group does the excretion of total 17-KS increase significantly after corticotrophin administration. The fractional determination reveals no difference between the two groups of patients with regard to the values of the fractions U (unidentified 17-KS), A (androsterone) and Rest (11-oxygenated 17-KS). The excretion of dehydroepiandrosterone is significantly higher in the hyperemesis group than in the control group. The excretion of androstanolone seems to be lower in the hyperemesis group than in the control group, but the difference is not statistically significant. The differences in the correlation between dehydroepiandrosterone and androstanolone in the two groups is significant. The high excretion of dehydroepiandrosterone and low excretion of androstanolone in cases of hyperemesis gravidarum is a sign of adrenal dysfunction.

THE SUBJECT FIELD OF INSTITUTIONAL EDUCATION: THE SENSE AND PROSPECTS OF DEVELOPMENT IN UKRAINE

2020 ◽  
pp. 25-38
Author(s):  
Irina Mordous
Keyword(s):  
Decisive Role ◽  
Subject Field ◽  
National Education ◽  
Progressive Development ◽  
Separate Area ◽  
Economic Transformations ◽  
The Difference ◽  
The Individual ◽  
Political Economic

The development of modern civilization attests to its decisive role in the progressive development of institutions. They identified the difference between Western civilization and the rest of the world. Confirmation of the institutional advantages of the West was its early industrialization. The genesis and formation of institutionalism in its ideological and conceptualmethodological orientation occurs as a process alternative to neoclassic in the context of world heterodoxia, which quickly spread in social science. Highlighting institutional education as a separate area of sociocultural activity is determined by the factor of differentiation of institutional theory as a whole. A feature of institutional education is its orientation toward the individual and his/her transformation into a personality. The content of institutional education is revealed through the analysis of the institution, which includes a set of established customs, traditions, ways of thinking, behavioral stereotypes of individuals and social groups. The dynamics of socio-political, economic transformations in Ukraine requires a review of the foundations of national education and determination of the prospects for its development in the 21st century in the context of institutionalism.

scholarly journals Possibility of Human Gender Recognition Using Raman Spectra of Teeth

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 3983
Author(s):  
Ozren Gamulin ◽  
Marko Škrabić ◽  
Kristina Serec ◽  
Matej Par ◽  
Marija Baković ◽  
...  
Keyword(s):  
Raman Spectra ◽  
Principal Component ◽  
Support Vector ◽  
Gender Recognition ◽  
Proof Of Concept ◽  
Male And Female ◽  
Tooth Type ◽  
Tooth Apex ◽  
The Difference

Gender determination of the human remains can be very challenging, especially in the case of incomplete ones. Herein, we report a proof-of-concept experiment where the possibility of gender recognition using Raman spectroscopy of teeth is investigated. Raman spectra were recorded from male and female molars and premolars on two distinct sites, tooth apex and anatomical neck. Recorded spectra were sorted into suitable datasets and initially analyzed with principal component analysis, which showed a distinction between spectra of male and female teeth. Then, reduced datasets with scores of the first 20 principal components were formed and two classification algorithms, support vector machine and artificial neural networks, were applied to form classification models for gender recognition. The obtained results showed that gender recognition with Raman spectra of teeth is possible but strongly depends both on the tooth type and spectrum recording site. The difference in classification accuracy between different tooth types and recording sites are discussed in terms of the molecular structure difference caused by the influence of masticatory loading or gender-dependent life events.

First models for structural energy transmission decoupling in the high frequency regime under aerodynamic excitations

2021 ◽  
pp. 095440622110200
Author(s):  
G Mazzeo ◽  
MN Ichchou ◽  
G Petrone ◽  
O Bareille ◽  
S De Rosa ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Vibrational Energy ◽  
Complex Structure ◽  
Structural Response ◽  
Test Case ◽  
Analysis Model ◽  
Quick Method ◽  
Vibrational Velocity ◽  
Frequency Regime ◽  
The Difference

In the wind tunnel facility, a test structure is often used for measuring its vibrational response to the aerodynamic excitation. A support is needed to sustaining the structure and it is mandatory that this support does not influence the vibrational energy to be measured. To this aim, the maximum amount of energy decoupling between the structure and the support is desired. This work is focused around a quick method to estimate this decoupling by using simplified models for the Turbulent Boundary Layer (TBL) excitation and for the structural response. Specifically, the Equivalent Rain-on-the-roof excitation is invoked with a Statistical Energy Analysis model for the structure. Some simple design rules are proposed and based on little information leading to foresee the difference of vibrational velocity levels between the two structural systems. A simplified test-case is used for the first investigations and a complex structure is finally conceived thinking to vibroacoustic measurements in a large wind tunnel facility. Although some results are largely expected, the global approach is promising.

scholarly journals Influence of Erythrocytes on Direct Potentiometric Determination of Sodium and Potassium

1983 ◽  
Vol 20 (2) ◽  
pp. 116-120 ◽  
Author(s):  
P Bijster ◽  
H L Vader ◽  
C L J Vink
Keyword(s):  
Whole Blood ◽  
Potassium Concentration ◽  
Reference Electrode ◽  
Sodium Concentration ◽  
General Phenomenon ◽  
Liquid Junction ◽  
Direct Potentiometry ◽  
The Difference ◽  
Sodium And Potassium

We have shown that the sodium concentration in whole blood measured by direct potentiometry is higher than in plasma. The ‘erythrocyte-effect’, already described by Siggaard Andersen, is most pronounced for instruments equipped with a reference electrode with an open static liquid junction and is thus a general phenomenon. Instruments with a modified liquid junction show less interference. The same phenomenon appears for the determination of the potassium concentration, although the difference between whole blood and plasma, when measured with instruments equipped with a modified liquid junction, can be neglected in practice.

Method for the simultaneous quantification of n-hexane metabolites: application to n-hexane metabolism determination

1996 ◽  
Vol 15 (6) ◽  
pp. 497-503 ◽  
Author(s):  
T. Soriano ◽  
M. Menéndez ◽  
P. Sanz ◽  
M. Repetto
Keyword(s):  
Similar Pattern ◽  
Analytical Procedure ◽  
Daily Basis ◽  
Practical Application ◽  
Simultaneous Quantification ◽  
Exposed Workers ◽  
Before And After ◽  
Time Requirements ◽  
The Difference

1 The described analytical procedure permits the simultaneous determination of the main n-hexane meta bolites in urine. 2-Hexanone, 2-hexanol, 2, 5-hexanediol and 2, 5-hexanedione, were chosen to dose the rats used in this study. All urine samples were collected and analysed on a daily basis, before and after acidic hydrolysis (pH 0.1) by GC/MS. 2-Hexanone, 2, 5-dimethylfurane, γ-valerolac tone and 2, 5-hexanedione were determined before hydro lysis ; 2-hexanol and 2, 5-hexanediol, after hydrolysis; and 5-hydroxy-2-hexanone and 4, 5-dihydroxy-2-hexanone were calculated by the difference between γ-valerolactone and 2, 5-hexanedione with and without hydrolysis, respectively. 2 A metabolic scheme was proposed reflecting the biotransformations undergone by the four compounds assayed. We consider 2, 5-dimethylfurane as a 'true metabolite' because the quantities detected were always greater before hydrolysis. 3 It has been reported that human and rat n-hexane metabolism follow a similar pattern. Therefore, as a practical application and without increasing either sample or time requirements, the simultaneous quantifi cation of the different metabolites and their excretion profile could provide better information about the metabolic situation of exposed workers than the determi nation of 2, 5-hexanedione alone. According to our experimental results, 4, 5-dihydroxy-2-hexanone itself would be a good toxicity indicator.

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