Verification of the material resistance factors in the CSA-S474 code for offshore concrete structures

1993 ◽  
Vol 20 (4) ◽  
pp. 660-671 ◽  
Author(s):  
Maher A. Nessim ◽  
Han Ping Hong ◽  
James G. MacGregor
Keyword(s):  
Structural Reliability ◽  
Concrete Strength ◽  
Concrete Structures ◽  
Steel Structures ◽  
Offshore Structures ◽  
Class I ◽  
Test Cases ◽  
Resistance Factors ◽  
Using Data

The Canadian Standards Association has developed a national code for the design, construction and installation of fixed offshore structures. This code was developed on the basis of probabilistic principles. It consists of five parts (CAN/CSA-S471 to S475), dealing with general loading and design requirements, foundations, steel structures, concrete structures, and sea operations. The material resistance factors cited in the part on concrete structures (S474-M1989) were verified using data typical of offshore structures for a set of representative design cases. The test cases were based on reinforced concrete ice resisting walls with configurations typical of those contemplated for offshore structures in Canada. They covered rare and frequent ice loading for safety classes I and II under flexure, combined flexure and axial force, and shear. The test cases were designed according to the CSA and DnV code provisions, and the reliabilities associated with the resulting members were calculated and assessed. The results indicate that the reliabilities achieved by designing to the CSA standard for safety class I sections are greater than those obtained by designing to DnV rules for all cases considered. Designs carried out according to CSA-S474 meet the target reliabilities implied by CSA-S471 for values of the coefficient of variation of the in situ concrete strength of up to 12% and are, in many cases, very conservative. Sensitivity analysis of safety class I members suggests that the material resistance factors can be increased. Issues that need to be addressed in order to justify an increase in the factors include the acquisition of more data on in situ concrete strength and a more comprehensive consideration of the design conditions covered by the code. The overall consistency of the reliability levels associated with the CSA code can be improved by simultaneous verification of the material factors in CSA-S474 and the load criteria and factors in CSA-S471. Key words: concrete structures, offshore structures, code verification, structural reliability, in situ concrete strength.

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.

The effects of seawater on the integrity of offshore structures

1978 ◽  
Vol 76 (1-3) ◽  
pp. 95-114
Author(s):  
T. Hodgkiess
Keyword(s):  
Corrosion Fatigue ◽  
Concrete Structures ◽  
Steel Structures ◽  
Offshore Structures ◽  
Internal Environment ◽  
The North ◽  
Recent Developments ◽  
The North Sea ◽  
Corrosion Mechanisms ◽  
Basic Features

SynopsisThis paper reviews the knowledge of deterioration processes which occur when steel and concrete structures are situated in seawater. The basic corrosion mechanisms of steel, together with possible methods of protection, are outlined briefly. With regard to coatings and cathodic protection, recent developments to counteract the increasingly severe conditions encountered by oil-production platforms in the North Sea, are discussed. Concrete structures usually provide a naturally-inhibitive internal environment to confer protection from corrosion to encased steel reinforcements, but mention is made of the possibilities of such protection becoming ineffective during long service in severe offshore conditions.The basic features of corrosion fatigue are described in the light of recent research but some aspects, which are of great importance for the performance of steel structures, are shown to be not well documented or understood. Corrosion fatigue of concrete structures has not been studied extensively, a particularly neglected area being the elucidation of the fundamental mechanisms of deterioration.

Value of information of in situ inspections of mooring lines

2021 ◽  
pp. 1748006X2098740
Author(s):  
Jorge Mendoza ◽  
Jacopo Paglia ◽  
Jo Eidsvik ◽  
Jochen Köhler
Keyword(s):  
Pitting Corrosion ◽  
Value Of Information ◽  
Structural Reliability ◽  
Structural Safety ◽  
Statistical Dependence ◽  
Mooring System ◽  
Mooring Lines ◽  
Corrosion Condition ◽  
Chain Links

Mooring systems that are used to secure position keeping of floating offshore oil and gas facilities are subject to deterioration processes, such as pitting corrosion and fatigue crack growth. Past investigations show that pitting corrosion has a significant effect on reducing the fatigue resistance of mooring chain links. In situ inspections are essential to monitor the development of the corrosion condition of the components of mooring systems and ensure sufficient structural safety. Unfortunately, offshore inspection campaigns require large financial commitments. As a consequence, inspecting all structural components is unfeasible. This article proposes to use value of information analysis to rank identified inspection alternatives. A Bayesian Network is proposed to model the statistical dependence of the corrosion deterioration among chain links at different locations of the mooring system. This is used to efficiently update the estimation of the corrosion condition of the complete mooring system given evidence from local observations and to reassess the structural reliability of the system. A case study is presented to illustrate the application of the framework.

The Suitability of an in Situ Perfusion Model for Permeability Determinations:  Utility for BCS Class I Biowaiver Requests

2006 ◽  
Vol 3 (6) ◽  
pp. 686-694 ◽  
Author(s):  
Jae-Seung Kim ◽  
Stefanie Mitchell ◽  
Paul Kijek ◽  
Yasuhiro Tsume ◽  
John Hilfinger ◽  
...  
Keyword(s):  
Class I ◽  
In Situ Perfusion ◽  
Perfusion Model

Gamma-ray spectrometer calibration for field analysis of thorium, uranium and potassium

1970 ◽  
Vol 7 (4) ◽  
pp. 1093-1098 ◽  
Author(s):  
P. G. Killeen ◽  
C. M. Carmichael
Keyword(s):  
Regression Analysis ◽  
Gamma Ray ◽  
Laboratory Analysis ◽  
In Situ Analysis ◽  
Field Analysis ◽  
Gamma Ray Spectrometer ◽  
Nonlinear Relation ◽  
Using Data ◽  
Spectrometer Calibration

The calibration of a portable three-channel gamma-ray spectrometer for in situ analysis of thorium, uranium, and potassium is discussed. A method of regression analysis is suggested as the best means of including all of the data available from the calibration stations. Calibration indicates a nonlinear relation between count rates obtained in the field and concentrations in parts per million obtained from laboratory analysis. The range of radioelement content must be taken into consideration and appropriate sets of calibration constants applied. As an example of the method, calibration constants are calculated for a portable gamma-ray spectrometer using data for the Blind River uranium region of Ontario.

Causes of Structural Failures with Steel Structures

2017 ◽  
Author(s):  
Goran Alpsten
Keyword(s):  
Structural Damage ◽  
Human Error ◽  
Structural Reliability ◽  
Steel Structures ◽  
Fatigue Loading ◽  
Structural Instability ◽  
Human Errors ◽  
Collapse Mode ◽  
Load Carrying ◽  
Structural Failures

This paper is based on the experience from investigating over 400 structural collapses, incidents and serious structural damage cases with steel structures which have occurred over the past four centuries. The cause of the failures is most often a gross human error rather than a combination of “normal” variations in parameters affecting the load-carrying capacity, as considered in normal design procedures and structural reliability analyses. Human errors in execution are more prevalent as cause for the failures than errors in the design process, and the construction phase appears particularly prone to human errors. For normal steel structures with quasi-static (non-fatigue) loading, various structural instability phenomena have been observed to be the main collapse mode. An important observation is that welds are not as critical a cause of structural steel failures for statically loaded steel structures as implicitly understood in current regulations and rules for design and execution criteria.

Hedonic experiences at heritage attractions: the visitor’s perspective

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ana Carolina Bender ◽  
Manuela Guerreiro ◽  
Bernardete Dias Sequeira ◽  
Júlio Mendes
Keyword(s):  
Design Methodology ◽  
Theory And Practice ◽  
Structured Interviews ◽  
Content Type ◽  
Heritage Sites ◽  
Exploratory Approach ◽  
Hedonic Experience ◽  
Using Data

Purpose The purpose of this study is to explore the hedonic experience and its formation at heritage attractions. Design/methodology/approach A qualitative and exploratory approach was applied, using data from 21 semi-structured interviews and three in-situ focus groups. Findings Findings highlight that senses, imagery and emotions are stimulated by the physical landscape and by triggers of memorable experiences. Research limitations/implications To further explore this topic, a broader range of heritage attractions and perspectives from the diverse stakeholders involved in the management and consumption of these sites is needed. Originality/value Given the scarcity of research dedicated to the hedonic experience at heritage sites, this study provides a contribution by exploring the visitor’s perspective and points out relevant insights. As the hedonic feelings of pleasure, comfort and related affective responses impact the quality of memorable experiences, relevant implications for theory and practice are discussed.

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