iPresas Risk Analysis

Valencia, Spain

iPresas Risk Analysis

Valencia, Spain
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Escuder-Bueno I.,Polytechnic University of Valencia | Mazza G.,RSE SpA | Morales-Torres A.,iPresas Risk Analysis | Castillo-Rodriguez J.T.,Polytechnic University of Valencia
Engineering | Year: 2016

In recent years, risk analysis techniques have proved to be a useful tool to inform dam safety management. This paper summarizes the outcomes of three themes related to dam risk analysis discussed in the Benchmark Workshops organized by the International Commission on Large Dams Technical Committee on “Computational Aspects of Analysis and Design of Dams.” In the 2011 Benchmark Workshop, estimation of the probability of failure of a gravity dam for the sliding failure mode was discussed. Next, in 2013, the discussion focused on the computational challenges of the estimation of consequences in dam risk analysis. Finally, in 2015, the probability of sliding and overtopping in an embankment was analyzed. These Benchmark Workshops have allowed a complete review of numerical aspects for dam risk analysis, showing that risk analysis methods are a very useful tool to analyze the risk of dam systems, including downstream consequence assessments and the uncertainty of structural models. © 2016 THE AUTHORS

Morales-Torres A.,iPresas Risk Analysis | Serrano-Lombillo A.,Polytechnic University of Valencia | Escuder-Bueno I.,Polytechnic University of Valencia | Altarejos-Garcia L.,Technical University of Cartagena
Structure and Infrastructure Engineering | Year: 2016

Risk analysis can provide very suitable and useful information to manage the safety of critical civil infrastructures. Indeed, results of quantitative risk models can be used to inform prioritisation of safety investments on infrastructures’ assets and portfolios. In order to inform this prioritisation, a series of risk reduction indicators can be used. This paper reviews existing indicators for dam safety, tracks how equity and efficiency principles are captured, propose additional indicators and provides insights into how tolerability guidelines and benefit–cost analysis can also play a role in decision-making. All reviewed, analysed and/or combined indicators are later applied in a case study, a portfolio of 27 dams where 93 structural and non-structural investments are prioritised. The case study shows that prioritisation sequences based on risk model results provide suitable and useful information, acknowledging that other concerns may be conditioning decision-making processes. With the results of the case study, a full comparison between all studied risk reduction indicators is made, and three indexes are calculated for all of them to measure how close they are to a theoretical best. © 2016 Taylor & Francis

Morales-Torres A.,iPresas Risk Analysis | Escuder-Bueno I.,Polytechnic University of Valencia | Altarejos-Garcia L.,Technical University of Cartagena | Serrano-Lombillo A.,Polytechnic University of Valencia
Engineering Structures | Year: 2016

In the majority of engineering problems, two kinds of uncertainty are generally considered: natural uncertainty, resulting from the inherent variability in natural processes, and epistemic uncertainty, linked to lack of knowledge. When performing a quantitative risk analysis, considering both types of uncertainty separately before integrating them when performing risk calculations, allows a better understanding on how both types of uncertainty influence risk results. The main purpose of this paper is presenting a consistent procedure to perform fragility analysis for dams in order to identify and track natural and epistemic uncertainty separately. This procedure is particularized for the sliding failure mode of concrete gravity dams, due to its importance. The resulting fragility curves provides a valuable input to quantitative risk models in order to compare the effect of risk reduction and uncertainty reduction investments. The proposed procedure combines the concepts of the Electrical Power Research Institute (EPRI) guidelines to develop fragility curves for the nuclear industry with existing reliability techniques for computing fragility curves in the context of concrete dams engineering. The procedure has been applied to a dam to illustrate how it can be used in a real case in such a manner that fragility curves are obtained integrating natural and epistemic uncertainties without losing track of their separate contribution to risk results. © 2016

Altarejos-Garcia L.,Technical University of Cartagena | Escuder-Bueno I.,Polytechnic University of Valencia | Morales-Torres A.,IPresas Risk Analysis
Materials | Year: 2015

Failure analysis of the dam-foundation interface in concrete dams is characterized by complexity, uncertainties on models and parameters, and a strong non-linear softening behavior. In practice, these uncertainties are dealt with a well-structured mixture of experience, best practices and prudent, conservative design approaches based on the safety factor concept. Yet, a sound, deep knowledge of some aspects of this failure mode remain unveiled, as they have been offset in practical applications by the use of this conservative approach. In this paper we show a strategy to analyse this failure mode under a reliability-based approach. The proposed methodology of analysis integrates epistemic uncertainty on spatial variability of strength parameters and data from dam monitoring. The purpose is to produce meaningful and useful information regarding the probability of occurrence of this failure mode that can be incorporated in risk-informed dam safety reviews. In addition, relationships between probability of failure and factors of safety are obtained. This research is supported by a more than a decade of intensive professional practice on real world cases and its final purpose is to bring some clarity, guidance and to contribute to the improvement of current knowledge and best practices on such an important dam safety concern. © 2015 by the authors.

Altarejos-Garcia L.,Polytechnic University of Valencia | Escuder-Bueno I.,Polytechnic University of Valencia | Serrano-Lombillo A.,IPresas Risk Analysis | de Membrillera-Ortuno M.G.,Polytechnic University of Valencia
Structural Safety | Year: 2012

Dam safety based on risk analysis methodologies demand quantification of the risk of the dam-reservoir system. This means that, for a given initial state of the system, and for the several failure modes considered, it is necessary to estimate the probability of the load events and the conditional probability of response of the system for a given load event, as well as estimating the consequences on the environment for the obtained response of the system. The following paper focuses in the second of these probabilities, that is, quantifying the conditional probability of response of the system, for a given load event, and for the specific case of concrete gravity dams. Dam-reservoir systems have a complex behavior which has been tackled traditionally by simplifications in the formulation of the models and adoption of safety factors. The purpose of the methodology described in this paper is to improve the estimation of the conditional probability of response of the dam-reservoir system for concrete gravity dams, using complex behavior models based on numerical simulation techniques, together with reliability techniques of different levels of precision are applied, including Level 3 reliability techniques with Monte Carlo simulation. The paper includes an example of application of the proposed methodology to a Spanish concrete gravity dam, considering the failure mode of sliding along the rock-concrete interface. In the context of risk analysis, the results obtained for conditional probability of failure allow several conclusions related to their validity and safety implications that acquire a significant relevance due to the innovation of the study performed. © 2012 Elsevier Ltd.

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