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1
Content available Risk assessment approaches for offshore structures
Shouman M., Ghoneim N. I., El-Khatib M.
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
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2021
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Vol. 15 No. 2
401--406
EN
Risk assessment and management was established as a scientific field some 30–40 years ago. Principles and methods were developed for how to conceptualize, assess, and manage risk. These principles and methods still represent largely the foundation of this field today, but many advances have been made, linked to both the theoretical platform and practical models and procedures. The purpose of the thesis is to perform a review of these advances, with a special focus on the fundamental ideas and thinking on which these are based. We have looked for trends in perspectives and approaches, and we reflect on where further development of the risk field is needed and should be encouraged. The present study is written for readers with different types of background, not only for experts on risk. However, there is a conflict between the cost impact and safety aspect. E&P managers as well as government supervisor authorities are constantly faced with decisions to be made regarding of safety. In order to ensure comparability and to set priorities application of QRA is a useful tool to justify choices made with regard to personnel safety, environmental protection, asset damage and business reputation, it is recommended to apply the systematic cause analysis method and develop the risk management models which contains an integral approach toward the health, safety and environmental aspect.
2
Content available Bioactive ceramic coating solution for offshore floating wind farms
Sanz D. S.., García S., Trueba L., Trueba A.
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
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2021
|
Vol. 15 No. 2
407--412
EN
Biofouling is a natural phenomenon that consists of the accumulation of living organisms on an artificial surface submerged or in contact with water like Offshore platforms. This study highlights the need for offshore floating wind farms structures to consider the choice of material used in offshore applications to minimize microbial-associated and corrosion problems. For this purpose, differences in the total of seawater biofouling attached on two coated paints and three ceramic coatings in carbon steel for offshore structures were evaluated and compared. All ceramic coatings were made of incorporating, by electrophoretic deposition, active ceramic particles against biofouling as copper, silver, zinc and titanium. This experiment consisted of testing ceramic coatings and conventional paints in a real environment with high biological activity and at the same time in a shallow marine environment for a period of 1 year, which provided positive comparisons with the standard system (ASTM-D3623) for using in protecting offshore marine structures.
3
Content available Spectral response of stationary jack-up platforms loaded by sea waves and wind using perturbation method
Rozmarynowski Bogdan, Jesien Wojciech
Polish Maritime Research
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2021
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nr 4
53--62
EN
The paper addresses non-linear vibrations of offshore jack-up drilling platforms loaded by sea waves and wind in their stationary condition using the perturbation method. Non-linearity of dynamic equations of motion for fixed offshore platforms yields from two factors. The first is load excitation generating non-linear velocity coupling in a dynamic system. This coupling is inherent in the modified Morison equation, involving the excitation function in the form of the sum of the inertial and velocity forces of sea waves, taking into account relative wave–structure kinematics. Moreover, the wind acting on the exciting side causes similar effects. The second source is the subsoil‒structure interaction problem, modelled by a system of springs and dashpots that yields stochastic non-linearity of the dynamic system. The matrix equations of structural motion in FEM terms are set up. The perturbation method is adopted to determine the mechanical response of the system, making it possible to determine response spectra of the first and the second approximations for displacements and internal forces of the platform. The paper is the continuation of research detailed in the paper [1]. It is assumed, that the fluctuation parts of the dynamic loading forces are in line with the direction of sea wave propagation. Sea current and lift forces effects are neglected in this study. A numerical example refers to structural data of the Baltic drilling platform in the stationary configuration, i.e. when three legs support the deck above the seawater level.
4
Content available Structural assessment of the hull response of an fpso unit to dropped objects: a case study
Ozguc Ozgur
Polish Maritime Research
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2019
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nr 4
39--46
EN
Offshore structures are exposed to the risk of damage caused by various types of extreme and accidental events, such as fire, explosion, collision, and dropped objects. These events cause structural damage in the impact area, including yielding of materials, local buckling, and in some cases local failure and penetration. The structural response of an FPSO hull subjected to events involving dropped objects is investigated in this study, and non-linear finite element analyses are carried out using an explicit dynamic code written LS-DYNA software. The scenarios involving dropped objects are based on the impact from the fall of a container and rigid mechanical equipment. Impact analyses of the dropped objects demonstrated that even though some structural members were permanently deformed by drop loads, no failure took place in accordance with the plastic strain criteria, as per NORSOK standards. The findings and insights derived from the present study may be informative in the safe design of floating offshore structures.
5
Content available Spectral dynamic analysis of a stationary jack-up platform
Rozmarynowski Bogdan
Polish Maritime Research
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2019
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nr 1
40--48
EN
The paper refers to the dynamic short-term response analysis of the Baltic steel drilling platform (see Fig.2) in a random sea-state represented by one-dimensional wave spectrum proposed by Striekalov and Massel, which is recommended for the Baltic Sea area. The Baltic drilling platform is a jack-up type platform for the exploration and exploitation of oil under the Baltic Sea. The presented analysis deals with the stationary phase of the platform life when its legs are fixed in the sea bottom. The submerged elements of jack-up platforms are relatively slender, thus to assess the in-line wave forces a modified Morison equation is justified. The application of frequency transfer functions to offshore vibration systems leads to structural response spectra whose input is defined by the wave elevation and wind velocity spectra. The analysis can be applied also to support structures for offshore wind turbines.
6
Content available Hybrid finite element method development for offshore structures’ calculation with the implementation of industry standards
Łubiński Jacek, Olszewski Henryk
Polish Maritime Research
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2019
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nr 4
90--100
EN
In the design process of offshore steel structures, it is typical to employ commercial calculation codes in which simulation and evaluation of results are performed on the basis of the available standards (e.g. API, DNV, Lloyds). The modeling and solution rely on finite element methods and cover the simulation of the structure’s properties along with the influence of the marine environment – sea currents, wave and wind loading, as well as the influence of vibrations, buoyancy and accompanying mass of water. Both commercial and open source mathematical modeling software which is available nowadays allows for cost effective and flexible implementation of advanced models for offshore industrial structures with high level of credibility and safety. The models can be built to suit task-specific requirements and evaluated on the basis of the selected criterial system best suited to the needs of the customer. Examples of methodology for environmental and structural model development are presented, along with simulation results covering a wide scope of data, ranging from stress and deformation to resonant characteristics and issues of technological feasibility.
7
Content available Selected problems of sensitivity and reliability of a jack-up platform
Rozmarynowski B., Mikulski T.
Polish Maritime Research
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2018
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nr 1
77--84
EN
The paper deals with sensitivity and reliability applications to numerical studies of an off-shore platform model. Structural parameters and sea conditions are referred to the Baltic jack-up drilling platform. The sudy aims at the influence of particular basic variables on static and dynamic response as well as the probability of failure due to water waves and wind loads. The paper presents the sensitivity approach to a generalized eigenvalue problem and evaluation of the performace functions. The first order time-invariant problems of structural reliability analysis are under concern.
8
Content available Influence of pitting corrosion on fatigue and corrosion fatigue of ship and offshore structures. Part II: load - pit - crack interaction
Jakubowski M.
Polish Maritime Research
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2015
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nr 3
57--66
EN
In the paper has been discussed influence of stresses on general corrosion rate and corrosion pit nucleation rate and growth , whose presence has been questioned by some authors but accepted by most of them. Influence of roughness of pit walls on fatigue life of a plate suffering pit corrosion and presence of the so called „ non-damaging” pits which never lead to initiation of fatigue crack, has been presented. Possibility of prediction of pit-to-crack transition moment by two different ways, i.e. considering a pit a stress concentrator or an equivalent crack, has been analyzed. Also, influence of statistical distribution of depth of corrosion pits as well as anticorrosion protection on fatigue and corrosion fatigue has been described.
9
Content available remote Technology of Welding Large-Sized Rings of Offshore Structures
Saperski M.
Biuletyn Instytutu Spawalnictwa w Gliwicach
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2015
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Vol. 59, No. 6
46--51
EN
The article presents practically proven technology for making single large-sized rings used in offshore structures and made of high strength steel rectangular segments (100 mm x 120 mm). The study also presents formal and documentationrelated requirements as well as issues concerning quality assurance.
PL
Przedstawiono sprawdzoną w praktyce technologię wytwarzania w produkcji jednostkowej wielkogabarytowych pierścieni dla konstrukcji offshore, wykonanych z segmentów profili prostokątnych o przekroju 100 x 120 mm, ze stali o podwyższonej wytrzymałości. Omówiono również wymagania formalne, dokumentacyjne i zagadnienia zapewnienia jakości.
10
Content available Influence of pitting corrosion on fatigue and corrosion fatigue of ship structures. Part I Pitting corrosion of ship structures
Jakubowski M.
Polish Maritime Research
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2014
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nr 1
62--69
EN
The present paper is a literature survey focused on a specific kind of corrosion, i.e. pitting corrosion and its influence on fatigue of ship and offshore steels. Mechanisms of a shortand long-term pitting corrosion in marine environment have been described including pit nucleation and growth phases. Some models of pit growth versus time of exposure have been presented. Some factors which influence the pit growth rate have been discussed briefly.
11
Content available Podstawy budowy modelu niezawodnościowego elementów nośnych konstrukcji oceanotechnicznych
Rosochacki W.
Zeszyty Naukowe / Akademia Morska w Szczecinie
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2009
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nr 19 (91)
92-96
PL
W artykule podjęto temat podstaw budowy matematycznego modelu niezawodności elementów nośnych konstrukcji okrętowych probabilistycznie jednorodnych. W modelu uwzględniono trzy typy uszkodzeń: trwałe odkształcenie plastyczne, pęknięcia zmęczeniowe oraz utratę stateczności lokalnej. W szczególności zaproponowano i określono cechy i granice obszarów zdatności. Proponowany model uwzględnia zmiany właściwości elementu jako skutku działania obciążeń cyklicznych.
EN
The paper describes basis of the model for reliability analysis of probabilistically homogenous offshore structures bearings. Three types of damages were considered: permanent plastic strain, fatigue crack and local instability. Specifically, features and limits of ability areas were proposed and determined. In this article was also investigated the influence of variation of element properties as an effect of cyclic loading action.
12
Content available Finite element local analysis of wave slamming on offshore structure
Żyliński B.
Polish Maritime Research
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2009
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nr 1
8-12
EN
Offshore platforms are exposed to waves slamming event. Waves hitting the columns with a high velocity are in many cases the design criteria for column structure. This paper focuses on the analysis of wave slamming on floating platform column. Significant for wave slamming pressure is load history, which is usually based on model test. Wave slamming loads were defined on all four walls of column to assess the worst place. For south wall of column three positions exposed to slamming loads between elevation 21.000 (SWL) and elevation 35.500 were checked. Dynamic analysis has been performed with nonlinear FEM program ABAQUS /explicit. The steel was modeled as an elastic-plastic material with isotropic hardening.
13
Content available remote Konstrukcje "offshore" - klasyfikacja i wymagania.
Saperski J.
Biuletyn Instytutu Spawalnictwa w Gliwicach
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2007
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R. 51, nr 6
50-54
PL
Podano krótką charakterystykę konstrukcji "offsshore", do których należą różnego rodzaje platformy służące do wykonywania odwiertów, wydobywania, przeróbki i magazynowania ropy i gazu spod dna morskiego oraz statki wiertnicze, pływające magazyny i przetwórnie . Na przykładzie własnych doświadczeń omówiono specyfikę remontów platform eksploatowanych na Morzu Północnym, przeprowadzanych głównie w oparciu o norweskie normy Norsok.
EN
It has been characterized in short offshore structures which comprise platforms of different kinds designed for the manufacture of bore-holes, treatment and storage of oil and gas from under sea bottom as well drill ships, floating stores and processing plants. Basing on his own experience, the author discusses the specifies of repair of the platforms operating on the North Sea, carried out mainly according to the Norwegian Standards "Norsok".
14
Content available remote Natural frequencies of a multi-articulated tower immersed in still fluid
Uściłowska-Gajda A.
Vibrations in Physical Systems
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2002
|
Vol. 20
292--293
15
Content available remote Hydrodynamics of offshore structures under waves and current: fundamental theory, formulation of the problem and a case study
Mendes A. C.
Vibrations in Physical Systems
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2002
|
Vol. 20
34--57
EN
This lecture is devoted firstly to a statement of the physical properties of gravity waves that is followed by a review on Linear Theory of waves of small amplitude, together with the related basic equations. This material includes the calculation of water pressure and water-particle kinematics, and the establishment of mass, momentum and energy balances. On a second stage it will be given a comprehensive material concerning the methodologies applied to calculate the wave forces. In the present case we will be involved with the Morison model and the corresponding hydrodynamic coefficients, when predicting the wave forces exerted upon tubular structures. Finally, a case study will be presented, relating both theoretical and experimental results obtained with a physical model of an offshore jacket platform.
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