On an approach to the evaluation of the latent risk of expert assessment of roadbed seismic stability

Abstract

The paper aims to examine the problem of integration of the opinions of a group of experts regarding a certain probabilistic distribution for the purpose of its evaluation by an analyst. It is implied that the decision-maker will use the result to evaluate the target risks and take according decisions. This problem may arise in many areas of risk analysis. For the purpose of this paper, the stability of various structures (buildings, railways, highways, etc.) against external mechanical effects, e.g. earthquakes, is chosen as the application object domain. As the primary research tool it is suggested to use the probabilistic method of decision-making risk calculation associated with involving experts into the analysis of risk of roadbed and other structures destruction in case of earthquakes. The evaluation of the seismic stability of rail structures using expert opinions is based on the Bayesian approach. The proposed method of estimation by analyst of the probabilistic distribution (fragility curve) on the basis of the opinions of a group of experts allows, using the obtained results, formalizing and explicitly expressing the latent risk of expert assessment. The procedure developed subject to a number of limitations allowed obtaining an explicit expression for the latent risk of expert assessment. The theoretical constructs presented in this paper can be easily implemented as software that will enable interactive input of parameters and data of the model under consideration and obtaining the desired distribution and the value of “risk in risk”. Such system, on the one hand, will allow verifying some intuitive assumptions regarding the behavior of results depending on the variation of parameters, and on the other hand, will be able to be used as the tool of expert assessment automation and analysis of its quality that helps making grounded decisions under risk. Further development of the proposed method may involve the elimination of the dependence of the value of “risk in risk” from the expert assessment. Implicitly, this dependence is present in the final expression, while ideally this risk is to be determined only by the expert ratings. The proposed approach can serve as the foundation of some practical optimization problems, e.g. the selection of the best group of involved experts from the point of view of minimization of this share of risk in cases of restricted funding of expert assessment (obviously, the higher the expert’s competence, the more accurate his/her estimates are and, subsequently, the lower is the risk, yet the higher is the cost of such expert’s participation). An associated problem can be considered as well. It consists in the optimal selection of experts for the purpose of minimization of assessment costs under the specified maximum allowable level of “risk in risk”. As a whole, the proposed method of evaluation of an unknown distribution and calculation of risk is sufficiently universal and can be used in the context of mechanical stability of structures, but also a wide class of problems that involve the assessment of a certain probabilistic distribution on the basis of subjective data about it.