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Safety in Engineering
Structural Safety 24 (2002) 83–84 www.elsevier.com/locate/strusafe
Book review Safety in Engineering Transactions of 3rd. BBB Symposium on Safety in Engineering, Buenos Aires, August 2000, Academia Nacional de Ingenierı´a, Editorial Dunken, 2000 A scientific meeting, designated by the organizer as the Third BBB Symposium, was held in Buenos Aires in August 2000. The name was coined by Alberto Bernardini, as a humorous recognition of the participation of David Blockley, Arturo J. Bignoli and himself, in a series of encounters, the first of which took place in Padova in 1998. These encounters had the purpose of discussing basic issues of Safety in Engineering. The Transactions of the Buenos Aires Symposium, published by the National Academy of Engineering of Argentina, include in a single volume the presentations of the six invited lecturers. Although the Axiomatic Theory of Probability, as formulated by Kolmogorov, constitutes the basis for most developments in Structural Safety and Reliability, many recent applications resort to fuzzy sets—so-called Possibility Theory—or other alternative formulations. It is likely clear to most reliability experts that these formulations are merely different proposals to quantify uncertainty, but our notions turn instantly blurry when a more precise definition of meaning or when a measure of equivalence between the various concepts are desired. In his lecture, Bernardini presents a much needed unified treatment of (a) the standard Probability Theory, (b) Zadeh’s Fuzzy Sets or Possibility Theory, (c) Convex Modeling and (d) Interval Analysis, through the Theory of Random Sets. In addition to a discussion of basic concepts, Bernardini’s paper features an example of the assessment of evidence and an application to event tree analysis, which illustrate the scope of available approaches, rendering the contribution of interest both for researchers and engineers. Bignoli, on the assumption that there is always a clear distinction between objective and subjective knowledge, suggests a procedure to reduce the subjectivity of the latter. This may be achieved by getting the consent of various experts, each of whom has his own subjective opinion. Bignoli defines consent as a view accepted by all experts. Next, use of a weighted average of the qualifications given by the experts is proposed, with the weights decreasing with the distance to the prevalent view. This suggests that if the experts held divergent views, and the procedure leads to an outcome somewhere in the middle, it may conceivably represent nobody’s opinion. Thus, a prerequisite might be that the experts roughly agree on the matter. This poses an interesting problem, which should be addressed by the author in future contributions. In this paper, Bignoli devotes more attention to operational rules in applications. In engineering approaches to the issue of quality, two main streams may be readily identified: the use of so-called soft and hard systems or models. Loosely stated, according to Blockley and Ferraris, a hard system is any physical system without people, while a soft system involves people,
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Book review / Structural Safety 24 (2002) 83–84
as well as their opinions or intentions. Undoubtedly the core of structural reliability, including its most highly developed branch, computational reliability, belong in the first category, while most developments in the area of quality are soft. The fact and perhaps the problem, in the authors’ opinion, is that they rarely mix. Within this context, Blockley and Ferraris’ paper is indeed an innovative and refreshing contribution. They suggests a strategy to deal with the global problem, by modeling it as a set of interacting processes. All processes have an outcome, which allows the estimation of the degree of success of the global system, either deterministically or probabilistically. To achieve such a purpose, the authors resort to the use of both Interval Probabilities and Possibility Theory, illustrating the approach with an example. The remaining papers in the Transactions also address pertinent topics, such as the influence on reliability evaluations of slight variations in the (assumed) probability densities of the variables involved, tackled by Elishakoff, or practical problems of bridge safety and management, discussed by Fazio and Del Carril. In brief, the papers in this volume constitute thought provoking contributions to the study of the safety of engineering systems, in general, and to the prediction of performance of global systems, in particular. Professor Dr. Jorge D. Riera Department of Civil Engineering Federal University of Rio Grande do Sul Porto Alegre, RS, Brazil
PII: S0167-4730(01)00019-4
Book review Safety in Engineering Transactions of 3rd. BBB Symposium on Safety in Engineering, Buenos Aires, August 2000, Academia Nacional de Ingenierı´a, Editorial Dunken, 2000 A scientific meeting, designated by the organizer as the Third BBB Symposium, was held in Buenos Aires in August 2000. The name was coined by Alberto Bernardini, as a humorous recognition of the participation of David Blockley, Arturo J. Bignoli and himself, in a series of encounters, the first of which took place in Padova in 1998. These encounters had the purpose of discussing basic issues of Safety in Engineering. The Transactions of the Buenos Aires Symposium, published by the National Academy of Engineering of Argentina, include in a single volume the presentations of the six invited lecturers. Although the Axiomatic Theory of Probability, as formulated by Kolmogorov, constitutes the basis for most developments in Structural Safety and Reliability, many recent applications resort to fuzzy sets—so-called Possibility Theory—or other alternative formulations. It is likely clear to most reliability experts that these formulations are merely different proposals to quantify uncertainty, but our notions turn instantly blurry when a more precise definition of meaning or when a measure of equivalence between the various concepts are desired. In his lecture, Bernardini presents a much needed unified treatment of (a) the standard Probability Theory, (b) Zadeh’s Fuzzy Sets or Possibility Theory, (c) Convex Modeling and (d) Interval Analysis, through the Theory of Random Sets. In addition to a discussion of basic concepts, Bernardini’s paper features an example of the assessment of evidence and an application to event tree analysis, which illustrate the scope of available approaches, rendering the contribution of interest both for researchers and engineers. Bignoli, on the assumption that there is always a clear distinction between objective and subjective knowledge, suggests a procedure to reduce the subjectivity of the latter. This may be achieved by getting the consent of various experts, each of whom has his own subjective opinion. Bignoli defines consent as a view accepted by all experts. Next, use of a weighted average of the qualifications given by the experts is proposed, with the weights decreasing with the distance to the prevalent view. This suggests that if the experts held divergent views, and the procedure leads to an outcome somewhere in the middle, it may conceivably represent nobody’s opinion. Thus, a prerequisite might be that the experts roughly agree on the matter. This poses an interesting problem, which should be addressed by the author in future contributions. In this paper, Bignoli devotes more attention to operational rules in applications. In engineering approaches to the issue of quality, two main streams may be readily identified: the use of so-called soft and hard systems or models. Loosely stated, according to Blockley and Ferraris, a hard system is any physical system without people, while a soft system involves people,
84
Book review / Structural Safety 24 (2002) 83–84
as well as their opinions or intentions. Undoubtedly the core of structural reliability, including its most highly developed branch, computational reliability, belong in the first category, while most developments in the area of quality are soft. The fact and perhaps the problem, in the authors’ opinion, is that they rarely mix. Within this context, Blockley and Ferraris’ paper is indeed an innovative and refreshing contribution. They suggests a strategy to deal with the global problem, by modeling it as a set of interacting processes. All processes have an outcome, which allows the estimation of the degree of success of the global system, either deterministically or probabilistically. To achieve such a purpose, the authors resort to the use of both Interval Probabilities and Possibility Theory, illustrating the approach with an example. The remaining papers in the Transactions also address pertinent topics, such as the influence on reliability evaluations of slight variations in the (assumed) probability densities of the variables involved, tackled by Elishakoff, or practical problems of bridge safety and management, discussed by Fazio and Del Carril. In brief, the papers in this volume constitute thought provoking contributions to the study of the safety of engineering systems, in general, and to the prediction of performance of global systems, in particular. Professor Dr. Jorge D. Riera Department of Civil Engineering Federal University of Rio Grande do Sul Porto Alegre, RS, Brazil
PII: S0167-4730(01)00019-4