scholarly journals ASSESSMENT OF STRUCTURES SUBJECTED TO ACCIDENTAL ACTIONS USING CRISP AND UNCERTAIN FRAGILITY FUNCTIONS

2009 ◽  
Vol 15 (1) ◽  
pp. 95-104 ◽  
Author(s):  
Egidijus R. Vaidogas ◽  
Virmantas Juocevičius
Keyword(s):  
Prior Distribution ◽  
Epistemic Uncertainty ◽  
Mean Value ◽  
Fragility Functions ◽  
Sources Of Information ◽  
Industrial Facilities ◽  
Fragility Function ◽  
Damage Probability ◽  
Aleatory And Epistemic Uncertainty ◽  
Statistical Sample

An application of fragility functions to the assessment of potential damage due to an accidental action is analysed. The assessment is carried out as an estimation of the probability of a foreseeable damage event (damage probability). This probability is expressed as a mean value of a fragility function developed for the damage event under study. A Bayesian prior (posterior) distribution specified for this mean value is used as an estimate of the damage probability. The prior distribution is derived by transforming prior knowledge through the fragility function and “mapping” this knowledge on the scale of probability values. The technique of Bayesian bootstrap resampling is applied to update the prior distribution. The new information used for the updating consists of a relatively small number of experimental observations of the accidental action. To facilitate the updating, these observations are transformed into a fictitious statistical sample of fragility function values. The updating is first carried out with a fragility function which expresses aleatory uncertainty only. Then it is proposed how to perform the updating with the fragility function which quantifies both aleatory and epistemic uncertainty. This is done by discretising continuous distributions of the epistemic uncertainty related to values (parameters) of the fragility function. The proposed approach allows to utilise different sources of information for the damage assessment. A potential field of application of this approach is risk studies of hazardous industrial facilities. Santrauka Analizuojamas pažeidžiamumo funkcijų taikymas vertinant potencialius statybinių konstrukcijų pažeidimus avariniais poveikiais. Vertinimas atliekamas skaičiuojant galimos konstrukcijos pažaidos tikimybę. Ši tikimybė yra išreiškiama vidutine pažeidžiamumo funkcijos reikšme. Ta funkcija yra formuojama analizuojamam pažaidos įvykiui. Apriorinis ir aposteriorinis Bajeso skirstiniai yra taikomi pažaidos tikimybės reikšmei vertinti. Apriorinis skirstinys yra gaunamas pasinaudojant turima informacija apie avarinį poveikį ir transformuojant šią informaciją per pažeidžiamumo funkciją. Aposteriorinis skirstinys yra gaunamas pasitelkiant naują, eksperimentinę informaciją apie avarinį poveikį. Aposterioriniam skirstiniui gauti taikomas kartotinio statistinio ėmimo (būtstrapo) metodas. Naują informaciją sudaro eksperimentiniai avarinio poveikio charakteristikų matavimai, kurie tiksliai atitinka konstrukcijos ekspozicijos tiriamo poveikio situaciją. Apriorinis ir aposteriorinis skirstiniai išreiškia episteminį neapibrėžtumą vertinamos pažaidos tikimybės reikšmės atžvilgiu. Šie skirstiniai yra gaunami taikant tiek pažeidžiamumo funkciją, kuri išreiškia tik stochastinį neapibrėžtumą, tiek funkciją, kurios reikšmės yra neapibrėžtos epistemine prasme. Potenciali siūlomo metodo taikymo sritis yra pavojingų pramoninių objektų rizikos vertinimas.

Epistemic Uncertainties in Component Fragility Functions

2010 ◽  
Vol 26 (1) ◽  
pp. 41-62 ◽  
Author(s):  
Brendon A. Bradley
Keyword(s):  
Quality Assurance ◽  
Earthquake Engineering ◽  
Epistemic Uncertainty ◽  
Finite Size ◽  
Seismic Demand ◽  
Fragility Functions ◽  
Seismic Performance Assessment ◽  
Fragility Function ◽  
Documentation Quality ◽  
Performance Based Earthquake Engineering

This paper is concerned with the inclusion of epistemic uncertainties in component fragility functions used in performance-based earthquake engineering. Conventionally fragility functions, defining the probability of incurring at least a specified level of damage for a given level of seismic demand, are defined by a mean and standard deviation and assumed to have a lognormal distribution. However, there exist many uncertainties in the development of such fragility functions. The sources of epistemic uncertainty in fragility functions, their consideration, combination, and propagation are presented and discussed. Two empirical fragility functions presented in literature are used to illustrate the epistemic uncertainty in the fragility function parameters due to the finite size of the datasets. These examples and the associated discussions illustrate that the magnitude of epistemic uncertainties are significant and there are clear benefits of the consideration of epistemic uncertainties pertaining to the documentation, quality assurance, implementation, and updating of fragility functions. Epistemic uncertainties should therefore always be addressed in future fragility functions developed for use in seismic performance assessment.

Comparative Analysis of Methodologies for Uncertainty Propagation and Quantification

2017 ◽  
Author(s):  
Alessandra Cuneo ◽  
Alberto Traverso ◽  
Shahrokh Shahpar
Keyword(s):  
Engineering Design ◽  
Polynomial Chaos ◽  
Epistemic Uncertainty ◽  
Uncertainty Propagation ◽  
Computational Cost ◽  
Computational Effort ◽  
Optimization Under Uncertainty ◽  
Design Parameters ◽  
Test Case ◽  
Aleatory And Epistemic Uncertainty

In engineering design, uncertainty is inevitable and can cause a significant deviation in the performance of a system. Uncertainty in input parameters can be categorized into two groups: aleatory and epistemic uncertainty. The work presented here is focused on aleatory uncertainty, which can cause natural, unpredictable and uncontrollable variations in performance of the system under study. Such uncertainty can be quantified using statistical methods, but the main obstacle is often the computational cost, because the representative model is typically highly non-linear and complex. Therefore, it is necessary to have a robust tool that can perform the uncertainty propagation with as few evaluations as possible. In the last few years, different methodologies for uncertainty propagation and quantification have been proposed. The focus of this study is to evaluate four different methods to demonstrate strengths and weaknesses of each approach. The first method considered is Monte Carlo simulation, a sampling method that can give high accuracy but needs a relatively large computational effort. The second method is Polynomial Chaos, an approximated method where the probabilistic parameters of the response function are modelled with orthogonal polynomials. The third method considered is Mid-range Approximation Method. This approach is based on the assembly of multiple meta-models into one model to perform optimization under uncertainty. The fourth method is the application of the first two methods not directly to the model but to a response surface representing the model of the simulation, to decrease computational cost. All these methods have been applied to a set of analytical test functions and engineering test cases. Relevant aspects of the engineering design and analysis such as high number of stochastic variables and optimised design problem with and without stochastic design parameters were assessed. Polynomial Chaos emerges as the most promising methodology, and was then applied to a turbomachinery test case based on a thermal analysis of a high-pressure turbine disk.

Analysis of Seismic Fragility Functions of Highway Embankments

2020 ◽  
Author(s):  
Balázs Hübner ◽  
András Mahler
Keyword(s):  
Finite Element ◽  
Earthquake Engineering ◽  
Seismic Fragility ◽  
Response Analysis ◽  
Fragility Functions ◽  
Ground Response ◽  
Ground Response Analysis ◽  
Fragility Function ◽  
Damage States ◽  
Log Normal

Vulnerability assessment of structures is a vitally important topic among earthquake engineering researchers. Generally, their primary focus is on the seismic performance of buildings. Less attention is paid to geotechnical structures, even though information about the performance of these structures (e.g. road embankments, levees, cuts) during an earthquake is essential for planning remediation and rescue efforts after disasters. In this paper the seismic fragility functions of a highway embankment are defined following an analytical methodolgy. The technique is a displacement-based evaluation of seismic vulnerability. Displacements of an embankment during a seismic event are approximated by a 2-D nonlinear ground response analysis using the finite element method. The numerical model was calibrated based on the results of a 1-D nonlinear ground response analysis. The expected displacements were calculated for 3 different embankment heights and Peak Ground Acceleration (PGA) values between 0,05 and 0,35g. Based on the results of the 2-D finite element analysis, the relationship between displacements and different seismic intensity measures (PGA, Arias-intensity) was investigated. Different damage states were considered, and the probability of their exceedance was investigated. The seismic fragility functions of the embankments were developed based on probability of exceedance of these different damage states based on a log-normal fragility function. The legitimacy of using a log-normal fragility function is also examined.

On the quantification of aleatory and epistemic uncertainty using Sliced-Normal distributions

2019 ◽  
Vol 134 ◽  
pp. 104560 ◽  
Author(s):  
Luis G. Crespo ◽  
Brendon K. Colbert ◽  
Sean P. Kenny ◽  
Daniel P. Giesy
Keyword(s):  
Epistemic Uncertainty ◽  
Normal Distributions ◽  
Aleatory And Epistemic Uncertainty

scholarly journals Seismic vulnerability of vernacular Newari buildings in Nepal: observations and analysis of damage due to 1934, 1988, 2011, and 2015 earthquakes

2018 ◽  
Author(s):  
Dipendra Gautam ◽  
Hugo Rodrigues
Keyword(s):  
Seismic Vulnerability ◽  
Masonry Buildings ◽  
Fragility Functions ◽  
Masonry Structures ◽  
Collapse Prevention ◽  
Damage Probability Matrices ◽  
Damage Probability ◽  
Probability Matrices

Abstract. This paper reports the seismic vulnerability of vernacular Newari buildings based on the damage observations during four major earthquakes (1934, 1988, 2011 and 2015) that struck Bhaktapur city. Some specific features that contributed to collapse prevention in traditional masonry buildings are also highlighted in this paper. In this paper, we have outlined the insights of each earthquake using forensic interpretations and the recommendations by various researchers after 1934 and 1988 earthquakes are compared in terms of their implementation. With the help of damage database recorded during 1934, 1988 and 2015 earthquakes, we have created damage probability matrices and empirical fragility functions for traditional masonry structures. The fragility functions and damage probability matrices derived in this study highlight that most of the vernacular Newari buildings are likely to be collapsed in the case of strong to major earthquakes.

A multi-objective systems reliability approach for infrastructure design under aleatory and epistemic uncertainty

2021 ◽  
Vol 89 ◽  
pp. 102063
Author(s):  
Yasaman Shahtaheri ◽  
Adrian Rodriguez-Marek ◽  
Jesús M. de la Garza ◽  
Madeleine M. Flint
Keyword(s):  
Epistemic Uncertainty ◽  
Multi Objective ◽  
Infrastructure Design ◽  
Aleatory And Epistemic Uncertainty

Scenario- based multi- risk assessment on exposed buildings to volcanic cascading hazards

2020 ◽  
Author(s):  
Michael Langbein ◽  
Juan Camilo Gomez- Zapata ◽  
Theresa Frimberger ◽  
Nils Brinckmann ◽  
Roberto Torres- Corredor ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Built Environment ◽  
Latin American ◽  
Pyroclastic Flows ◽  
Volcanic Risk ◽  
Fragility Functions ◽  
Load Pressure ◽  
State Fragility ◽  
Fragility Function ◽  
Ash Fall

<p>In order to assess the building portfolio composition for a particular natural hazard risk assessment application, it is necessary to classify the built environment into schemas containing building classes. The building classes should also address the attributes which may control their vulnerability towards the different hazards associated with their failure mechanisms, which along with their respective fragility functions are representative of a particular study area. In the case of volcanic risk, former efforts have been carried out in developing volcanic related fragility functions, this has been done mostly for European, Atlantic islands and South Asian building types (SEDIMER, MIA VITA, VOLDIES, EXPLORIS, SAFELAND projects). However, in other parts of the globe, particular construction practices, materials, and even occupancies may describe very diverse building types with different degrees of vulnerability which may or not be compatible with the existing schemas and fragility functions (Spence et al. 2005, Zuccaro et al. 2013, Mavrouli et al. 2013, Jenkins et al. 2014, Torres-Corredor et al. 2017).</p><p>As highlighted by Zuccaro et al. 2018, since in the case of volcanic active areas, the built environment will not only be exposed to a single hazard but to several compound or cascading hazards (e.g. tephra fall, pyroclastic flows, lahars), with different time intervals between them, a dynamic vulnerability with cumulated damage on the physical assets would be the baseline upon a multi-risk- volcanic framework should be described. In this similar context, single- hazard but still multi-state fragility functions have been very recently used in order to set up damage descriptions independently on the reference building schema. We propose to generalize this novel approach and further extend it in the volcanic risk assessment context. To do so, the very first step was to generate a multi-hazard- building- taxonomy containing a set of exhaustive mutually exclusive building attributes. Upon that framework, a probabilistic mapping across single- hazards- building- schemas and damage states has been achieved.</p><p>This methodological approach has been tested under the RIESGOS project over a selected study area of the Latin American Andes Region. In this region, cities close to active volcanos have been experienced a non-structured grow, which is translated into a significantly vulnerable population living in non- engineering buildings that are highly exposed to volcanic hazards. The Cotopaxi region in Ecuador has been chosen in order to explore the ash falls and lahars damage contributions with several scenarios in terms of volcanic explosivity index (VEI). Local lahars simulations have been obtained at different resolutions. Moreover, probabilistic ash- fall maps have been recently obtained after exhaustive ash fall and wind direction measurements. Lahar flow- velocity and ash- fall load pressure were respectively used as intensity measures. Furthermore, local and foreign building schemas that define the building exposure models have been constrained through ancillary data, cadastral information, and remote individual building inspections, to then been associated with a multi-state fragility function. These ingredients have been integrated into this novel methodological scenario-based- multi-risk- volcanic assessment.</p>

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