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An enhanced reliability index for assessing margin of safety in structures
Published in Marc A. Maes, Luc Huyse, Reliability and Optimization of Structural Systems, 2020
The Enhanced Reliability Index quantifies the margin of safety for constructed systems and components. Safety is measured relative to how much a structure meets, or exceeds, its design requirements. Hence, we distinguish between the potential for failure and the chance of failure, the former begin characterized by our ERI and the latter conventionally quantified by probability theory. To compute an ERI it is necessary to: (1) understand a system’s design requirements, (2) assess a system’s current condition, and (3) quantify uncertainties in both design requirements and condition assessments. The ERI is not a measure of system reliability (i.e. not a metric for the probability of safety), rather it measures a system’s margin of safety within a domain where reliability estimates are constant. Reliability is a measure of the probability of “not-failing”; it does not indicate a system’s relative safety.
Reliability-Based Analysis and Life-Cycle Management of Load Tests
Published in Eva O.L. Lantsoght, Load Testing of Bridges, 2019
Dan M. Frangopol, David Y. Yang, Eva O. L. Lantsoght, Raphaël D. J. M. Steenbergen
For existing structures, the target reliability index is lower than that of a structure in the design stage (Stewart et al., 2001;Steenbergen and Vrouwenvelder, 2010). The following factors determine the target reliability index for assessment: consequences of failure, reference period, remaining service life, relative cost of safety, and importance of the structure. When the maintenance and repair costs are large and the consequences of failure are minor, lower reliability indices are tolerated as assessment result. These values result from a cost optimization that considers the structural cost, the cost of damage, and the probability of failure, seeFigure 9.5. For the loss of human life, a lower bound ofβ = 2.5 with a reference period of one year (Steenbergen and Vrouwenvelder, 2010) should be considered.
Bridge Management Objectives and Methodologies
Published in J.E. Harding, G.E.R. Parke, M.J. Ryall, Bridge Management 3, 2014
In reliability analysis of bridge components, the maximum traffic loading, impact factor, dead load, superimposed dead load, analysis uncertainty, strength of steel reinforcement or tendons, strength of concrete, area of steel, dimensions, etc can be treated as random variables and described using appropriate probability distributions. The reliability index or failure probability can be evaluated efficiently using the First Order (FORM) and Second Order (SORM) reliability methods.
A Bayesian approach to reliability of MSE walls
Published in Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards, 2021
Nezam Bozorgzadeh, Richard J. Bathurst
Therefore, Rm and Qm are also lognormally distributed. Different methods are available to calculate the reliability index (or probability of failure), with the most popular ones being approximation methods, such as FORM and SORM, and Monte Carlo simulation. These methods are not constrained to the simplifying assumptions made in this paper. For the pullout limit state of Equation (5) with lognormal Rm and Qm, however, simple closed-form solutions exist (e.g. Lemaire 2013):As discussed earlier, and emphasised in Figures 4 and 5 and Table 2, there is uncertainty associated with the parameters μλR, σλR, μλQ, σλQ in Equations (9a) and (9b) since they are estimated from data that show variability. Furthermore, in the Bayesian context, these uncertain parameters are modelled as probability distributions. This in turn means that the reliability index or probability of failure also has probability distributions.
Preliminary Reliability Allocation Method for Fusion Facility Based on Probabilistic Safety Assessment
Published in Fusion Science and Technology, 2019
Dagui Wang, Jin Wang, Liqin Hu, Jie Wu, Fang Wang
Up to now, many reliability works have been done for fusion facilities. Among these, the ITER Reliability, Availability, Maintainability, Inspectability (RAMI) project is probably the most successful and widely used in fusion engineering. The RAMI project is one of the main stages of the ITER technical risk control strategy that makes it possible to meet its availability requirement.3 The RAMI project was started in 2008. Up to 2010, this project has been applied to 16 out of 21 main systems of ITER (Ref. 4), but the main focus on the availability of a fusion reactor and the reliability analysis of the fusion reactor has not reflected safety requirements. The safety analysis of the fusion reactor mostly has used a deterministic approach, which usually uses conservative assumptions on the behavior of plant systems and is independent of reliability analysis of fusion reactors.5,6 Consequently, the behavior of the plant as evaluated could be rather different from the fact, even if in a sense it is beneficial to safety.7,8 And, the safety-related work does not consider the engineering requirements and could lead to unnecessary waste. Actually, the reliability of a fusion reactor is a key issue in the engineering process of the fusion reactor.9–12 The reliability index is a useful indicator to evaluate the reliability of the system. But, up to now, the reliability index of a fusion reactor, especially the safety-related components, has not been established. The reliability work of the fusion device is difficult to support the safety supervision of fusion reactors.
Towards standardisation of proof load testing: pilot test on viaduct Zijlweg
Published in Structure and Infrastructure Engineering, 2018
Eva Olivia Leontien Lantsoght, Rutger T. Koekkoek, Dick Hordijk, Ane de Boer
Safety against failure and sufficient capacity are related to a reliability index. In the Netherlands, different safety levels are used for the assessment of existing structures, as given in the Guidelines for the Assessment of Reinforced Concrete Bridges of the Ministry of Infrastructure and the Environment (Rijkswaterstaat, 2013) and in the Dutch code NEN 8700:2011 (Code Committee 351001, 2011a). An overview of these safety levels is given in Table 1. The value of γsw has been modified from the value prescribed in the codes for assessment. This modification results in a lower value of γsw that can be used in combination with proof load testing. The reason why the value of γsw can be lowered is that at the moment of proof load testing, the self-weight of the bridge can be considered as a deterministic value. The only element that remains to determine the load factor is then the model factor.