SYMPOSIUM. FIXED OFFSHORE STRUCTURES: THE NEW CODE OF PRACTICE BS 6235 . ICE, LONDON 15 NOVEMBER 1982. STEEL STRUCTURES AND ASSOCIATED SEA OP -ERATIONS.

1983 ◽  
Vol 74 (3) ◽  
pp. 573-576
Author(s):  
NR FIELDER ◽  
PL STUART ◽  
JD HARRISON ◽  
JG HICKS ◽  
RE JENNINGS ◽  
...  
Keyword(s):  
Steel Structures ◽  
Offshore Structures ◽  
Code Of Practice

scholarly journals Hybrid Finite Element Method Development for Offshore Structures’ Calculation with the Implementation of Industry Standards

2019 ◽  
Vol 26 (4) ◽  
pp. 90-100
Author(s):  
Jacek Łubiński ◽  
Henryk Olszewski
Keyword(s):  
Finite Element ◽  
Method Development ◽  
Structural Model ◽  
Model Development ◽  
Steel Structures ◽  
Cost Effective ◽  
Offshore Structures ◽  
Wind Loading ◽  
Hybrid Finite Element Method ◽  
Industry Standards

Abstract 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.

scholarly journals ON STANDARDIZATION OF LABORATORY SOIL TESTING IN OFFSHORE GEOTECHNICAL SURVEY

Gruntovedenie ◽  
2021 ◽  
Vol 1 (16) ◽  
pp. 16-52
Author(s):  
E.A. Voznesensky ◽  
◽  
A.S. Loktev ◽  
M.S. Nikitin ◽  
◽  
...  
Keyword(s):  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Offshore Structures ◽  
Soil Testing ◽  
National Standard ◽  
Gas Industry ◽  
Code Of Practice ◽  
Complete Section ◽  
Testing Practice ◽  
Russian Soil

Issues of laboratory soil studies standardization in offshore geotechnical survey are discussed in connection with the end of expertise of two new regulative documents – new edition of the Code of practice and Russian national standard developed on the basis of international ISO standard. Since these documents of different level belong also to different categories (geotechnical survey and oil and gas industry), the authors analyze their interrelation and consistency, from one hand, and the preparedness of Russian soil testing practice to implementation of the new standard which results from harmonization with international ones, from the other. Complete section of the standard draft related to soil laboratory testing is presented, preceded by commentary on some important issues regarding the implementation of its specific methodic statements. It is concluded that the new national GOST draft «Petroleum and natural gas industries. Specific requirements for offshore structures. Marine soil investigations» developed on ISO basis will be a useful document supported in general by Russian normative base but expanding a possible range of voluntary methods into well time-tested foreign approaches. This documents can be considered to be a toolkit annex to the Code of practice describing testing approaches beyond the scope of typical tasks

Applications of Probabilistic Fracture Mechanics to Offshore Structures

1988 ◽  
Vol 41 (2) ◽  
pp. 61-84 ◽  
Author(s):  
Finn Kirkemo
Keyword(s):  
Fracture Mechanics ◽  
Model Updating ◽  
Fatigue Cracks ◽  
Limit State ◽  
Steel Structures ◽  
Local Stress ◽  
Offshore Structures ◽  
And Performance ◽  
Fatigue Limit State ◽  
Life Predictions

For offshore structures the fatigue limit state is governing the structural dimensions of several members and joint connections. Safety against fatigue failure is achieved through a combination of design requirements and performance of in-service inspections with repair of detected fatigue cracks. A review of uncertainties involved in fatigue life predictions by fracture mechanics is presented with particular reference to steel structures. Sources of uncertainties considered are: environmental conditions, hydrodynamic loading, global structural analysis, local stress calculation at fatigue sensitive points, and fatigue crack growth modeling by fracture mechanics. A probabilistic model using the fracture mechanics in probabilistic form is presented. This model accounts for uncertainties in loading, initial and critical defect sizes, material parameters, and in the uncertainty related to computation of the stress intensity factor. Failure probabilities are computed by first-order reliability methods and sensitivity factors are determined. Model updating based on in-service inspection results is formulated. Uncertainties with respect to detecting a crack and to correctly sizing a crack are included. Experience on application of the analysis method is presented.

scholarly journals The Effect of Notch Depth on CTOD Values in Fracture Tests of Structural Steel Elements

2018 ◽  
Vol 25 (2) ◽  
pp. 85-91
Author(s):  
Jakub Kowalski ◽  
Janusz Kozak
Keyword(s):  
Brittle Fracture ◽  
Test Procedure ◽  
Charpy Impact ◽  
Steel Structures ◽  
Charpy Impact Test ◽  
Offshore Structures ◽  
The Arctic ◽  
Notch Depth ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement

Abstract In elements of steel structures working at low temperatures, there is a risk of appearance of brittle fracture. This risk is reduced through the use of certified materials having guaranteed strength at a given temperature. A method which is most frequently used to determine brittle fracture toughness is the Charpy impact test, preformed for a given temperature. For offshore structures intended to work in the arctic climate, the certifying institutions more and more often require Crack Tip Opening Displacement (CTOD) tests instead of conventional impact tests, especially for steel and welded joints of more than 40 mm in thickness in the case of high-strength steel, and more than 50 mm for the remaining steels. The geometry of specimens and the test procedure are standardised; however, these standards provide some margin for specimen notch depth. The paper analyses the effect of notch depth difference, within the range permitted by the standards, on the recorded CTOD values of a given material. The analysis was performed via numerical modelling of destruction of specimens with different notch geometries and further verification of the obtained numerical results in laboratory tests. The calculations were carried out at the Academic Computer Centre in Gdansk.

Background for Revision of DNV-RP-C203 Fatigue Analysis of Offshore Steel Structure

2005 ◽  
Author(s):  
Inge Lotsberg
Keyword(s):  
Steel Structure ◽  
Steel Structures ◽  
Offshore Structures ◽  
Fatigue Analysis ◽  
Time Interval ◽  
Fatigue Design ◽  
The World ◽  
New Research ◽  
Made In

The last revision of the DNV recommended practice “Fatigue Analysis of Offshore Steel Structures” is from October 2001. During use of this standard some feed back from designers around the world have been received. Also some new research in the area has been performed in the time interval from it was first developed. It is also realised that the document is being used for fatigue design of some other types of details and structures than was thought of when the document was originally developed. Therefore it was now found convenient to revise the document to incorporate the experience gained and new research and developments made in the area of fatigue of offshore structures the last 7 years since the main content for this recommended practice was developed.

Reliability and (Re)Assessment of Fixed Steel Structures

2011 ◽  
Author(s):  
Mike Efthymiou ◽  
Jan Willem van de Graaf
Keyword(s):  
Structural Reliability ◽  
Structural Integrity ◽  
Steel Structures ◽  
Performance Standards ◽  
Offshore Structures ◽  
Design Standards ◽  
Component Strength ◽  
Post Buckling ◽  
Exposure Levels ◽  
Joint Occurrence

This paper reviews the structural integrity and reliability of fixed steel offshore structures with a focus on improved models and incorporation of these models in design standards. Technical achievements in four key areas are reviewed which, when combined, resulted in a step improvement in the calculation of structural reliability. The first area is the extreme environmental loading on an offshore platform; the second area is the joint occurrence of waves, winds and currents, i.e. accounting for the fact that these do not, in general, peak at the same time and do not act in the same direction. The third area is the estimation of the ultimate strength of a fixed steel platform, accounting for component strength, including the buckling and post-buckling behaviour and the uncertainty in system strength. The fourth and final area is the integration of the above models to estimate the probability of failure. The historical performance of platforms and the improvements in successive editions of API RP 2A are reviewed; reliability targets appropriate for different exposure levels and corresponding performance standards are developed, aimed at harmonizing design practices worldwide. A differentiation is recommended between permanently manned L-1 installations and manned-evacuated L-1 installations in the Gulf of Mexico; this is because the consequences of failure are considerably different.

Spectral Fatigue and Stress Based Reliability Assessment of Offshore Steel Structures

2008 ◽  
Author(s):  
H. Karadeniz
Keyword(s):  
Spectral Analysis ◽  
Limit State ◽  
Steel Structures ◽  
Offshore Structures ◽  
Statistical Characteristics ◽  
Random Wave ◽  
State Function ◽  
Efficient Computation ◽  
Reliability Method ◽  
Stress Spectrum

Having summarized briefly uncertainties in spectral fatigue damages of offshore structures, this paper presents the formulation and procedure of an efficient computation of reliability estimates on basis of fatigue damages and stresses. Most of uncertainties are embedded in response characteristics of the stress process and the damage-model used. Uncertainties in stress statistical characteristics are associated with the modeling of structures, random wave environment, wave loading and the analysis used. In the fatigue damage, additional uncertainties arise from the modeling of damage-mechanism. These uncertainties are due to experimental fatigue data and structural joint configurations. All these uncertainties can be classified into the categories as a) those naturally inherent (aleatory) and b) those due to lack of knowledge (epistemic). The second part of the paper is devoted to a fast and efficient computation of the fatigue reliability. This algorithm prevents repetitive execution of spectral analysis procedure during the reliability iteration. In this technique, a suitable formulation of the stress spectrum is used with a model uncertainty parameter representing most of uncertainties in the stress spectrum. The failure function of the reliability analysis is expressed independently of the spectral analysis. For the stress based reliability calculation the mean stress-amplitude of the stochastic stress variation is used to define a limit state function. The related uncertainties are the same as those aforementioned. The advanced FORM reliability method is used to calculate the reliability index and to identify important uncertainty parameters. The procedure is demonstrated by an example jacket structure. The third part of the paper explains the inverse reliability method to determine some parameters, which may be deterministic or probabilistic, under required reliability constraints.

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