On the treatment of uncertainties in the development of fragility functions for earthquake loss estimation of building portfolios

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SummaryIn a related study developed by the authors, building fragility is represented by intensity-specific distributions of damage exceedance probability of various damage states. The contribution of the latter has been demonstrated in the context of loss estimation of building portfolios, where it is shown that the proposed concept of conditional fragility functions provides the link between seismic intensity and the uncertainty in damage exceedance probabilities. In the present study, this methodology is extended to the definition of building vulnerability, whereby vulnerability functions are characterized by hazard-consistent distributions of damage ratio per level of primary seismic intensity parameter-Sa(T 1 ). The latter is further included in a loss assessment framework, in which the impact of variability and spatial correlation of damage ratio in the probabilistic evaluation of seismic loss is accounted for, using test-bed portfolios of 2, 5, and 8-story precode reinforced concrete buildings located in the district of Lisbon, Portugal. This methodology is evaluated in comparison with current state-of-the-art methods of vulnerability and loss calculation, highlighting the discrepancies that can arise in loss estimates when the variability and spatial distributions of damage ratio, influenced by ground motion properties other than the considered primary intensity measure, are not taken into account. KEYWORDS damage ratio uncertainty and spatial correlation, event-based seismic loss estimation, hazard-consistent fragility and vulnerability | INTRODUCTIONIn the process of risk computations, several studies have demonstrated the importance of accounting for spatial cross correlation of ground motion residuals in the evaluation of portfolio losses (eg, Park et al, Weatherill et al, Silva, and Yoshikawa and Goda 1-4 ). However, when the correlation of uncertainty in vulnerability (ie, in the damage ratio residuals across a class of buildings) is incorporated in loss estimation procedures (eg, Silva et al 5 ), it is done such that when sampling the uncertainty in the vulnerability of 2 assets with the same building class (and same level of seismic intensity measure), the residuals are assumed to be either uncorrelated of perfectly correlated. 6 Furthermore, as demonstrated by Bradley 7 and Silva et al 8 in the context of component and building fragility, respectively, the propagation of uncertainty from fragility to vulnerability is related to the scatter of results to which a parametric (usually lognormal) fragility curve is fitted (ie, uncertainty associated with the regression; Figure 1A).Typically used parametric relationships such as the lognormal or beta probabilistic functions provide a good approximation to the vulnerability uncertainty that results from the scatter of possible fragilities ( Figure 1B; eg, Silva et al 5 ). For a given level of

Section: Conditional Fragility Functions: Validationmentioning

confidence: 86%

Section: Conditional Fragility Functions: Validationmentioning

confidence: 99%

Section: Conditional Fragility Functions: Validationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

On the treatment of uncertainty in seismic vulnerability and portfolio risk assessment

Sousa

Silva

Marques

et al. 2017

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Reduced‐order models for the seismic assessment of plan‐irregular low‐rise frame buildings

Ruggieri

Chatzidaki

Vamvatsikos

et al. 2022

A procedure is presented for deriving low‐complexity structural models to predict the global response of asymmetric‐plan low‐rise frame buildings for purposes of class‐level assessment. As a compromise between employing a full‐scale multi‐degree‐of‐freedom structural model versus an equivalent single‐degree‐of‐freedom one, the challenge is to create an idealized 3D structure with few degrees‐of‐freedom that can match the inelastic response of a building for which full knowledge of geometrical and mechanical properties is available. Such a 3D reduced‐order model can offset the computational cost related to performing multiple nonlinear dynamic analyses within the framework of Performance‐Based Earthquake Engineering. To this goal, rules and equations are proposed for achieving equivalence among the linear and nonlinear properties (e.g. mass, stiffness, strength) of the building analysed and the related 3D reduced‐order model. The procedure is applied on a sample of 15 existing reinforced‐concrete frame school buildings, from the province of Foggia in Southern Italy, for which the full numerical models are available. Both calibrated and uncalibrated reduced‐order models are created, exploring the limitations of the proposed order‐reduction in a real‐life case study.

Direct seismic loss estimation of predominantly plan‐symmetrical frame buildings using simplified nonlinear models

Jamšek

Babič

Dolšek

2022

The estimation of building seismic risk and loss utilising response history analysis is challenging, especially because the final objective is the seismic loss estimation for building stock. In this paper, this challenge is addressed by developing a simplified nonlinear structural model, which is capable of simulating the seismic response of predominantly plan-symmetrical reinforced concrete frame buildings subjected to ground motions in both horizontal directions. The simplified structural model is plugged into the direct seismic risk and loss estimation methodology. Its capabilities are then demonstrated by estimating the seismic risk and losses for a four-storey office building and a five-storey school building. For the analysed buildings, it is shown that the frequency of collapse, the expected annual loss and the frequency of exceedance of a given loss can be simulated with the same level of accuracy as in the case of the conventional structural model, but with greater numerical robustness and computational efficiency. Research is needed to better define the limitations of the introduced simplified model and extend the capabilities of simplified nonlinear models to more complex structural systems of plan-asymmetrical buildings.