Probabilistic Performance Analysis of Existing Buildings under Earthquake Loading (original) (raw)
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Recent developments in earthquake engineering indicate that probabilistic seismic risk analysis (PSRA) is becoming increasingly useful for the evaluation of structural performance in accordance with building codes. In recent years, the field of seismic resistance design has been undergoing a critical shift in focus from strength to performance. However, current earthquake resistant design procedures do not relate building performance to probability. A lack of sufficient empirical data has highlighted gaps in this research. This study integrated results from the analysis of structural fragility and seismic hazard in Taiwan to perform PSRA to examine the effectiveness of building code in mitigating the risks associated with earthquakes. Factors taken into account included the effect of construction materials, building height, and building age. The results of this study show that the probability of exceeding damage associated with the CP level in buildings of light steel, precast concrete, and masonry, exceeds 2%. These buildings fail to meet the performance objectives outlined in FEMA-273.
SEISMIC PERFORMANCE-BASED RELIABILITY OF BUILDING STRUCTURES
SEAOC's Vision 2000 and FEMA 273 defme performance objectives as that of achieving performance levels for given seismic hazard levels. However, due to uncertainties in seismic structural demands and capacities, these objectives are achievable only in a probabilistic sense. Therefore, defmitions of performance objectives must also include associated target reliabilities. Structural and nonstructural performance levels as defined in the Vision 2000 and 1999 Blue Book are somewhat imprecise. Thus, fuzzy sets are used to represent performance levels. A fuzzy relation is constructed between economic loss-to-value ratios and drift ratios. This relation is used to verify performance given the range of expected drift ratios. Limit state equations are proposed to indicate " failure " to achieve the performance level.
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The evaluation of seismic performance of existing masonry buildings is a critical issue in assessing the seismic vulnerability of the built environment. With this aim, non-linear static analysis is commonly used, but results are influenced significantly by the collapse criteria adopted, as well as by the assumptions about material properties and drift capacity of masonry walls. A methodology for the probabilistic assessment of the seismic risk index is proposed by means of an original non-linear pushover type algorithm developed by the authors. The main sources of uncertainties related to masonry parameters and their influence on seismic risk indices are identified by means of sensitivity analysis. Response surfaces for the seismic risk indices are thus defined through general polynomial chaos expansion in order to quantify the uncertainties in the resulting seismic risk index. Finally, a seismic performance classification is presented to help stakeholders to manage risks and define priorities for seismic retrofit. The methodology together with the outcomes is illustrated for a set of existing masonry buildings that are part of the school system in the Municipality of Florence.
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HAL (Le Centre pour la Communication Scientifique Directe), 2010
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Probabilistic seismic risk evaluation of reinforced concrete buildings
The main objective of this article is to propose a simplified methodology to assess the expected seismic damage in reinforced concrete buildings from a probabilistic point of view by using Monte Carlo simulation. In order to do so, the seismic behaviour of the building was studied by using random capacity obtained by considering the mechanical properties of the materials as random variables. From the capacity curves, the damage states and fragility curves can be obtained, and curves describing the expected seismic damage to the structure as a function of a seismic hazard characteristic can be developed. The latter can be calculated using the capacity spectrum and the demand spectrum according to the methodology proposed by the Risk-UE project. In order to define the seismic demand as a random variable, a set of real accelerograms were obtained from European and Spanish databases in such a way that the mean of their elastic response spectra was similar to an elastic response spectrum selected from Eurocode 8. In order to combine the uncertainties associated with the seismic action and the mechanical properties of materials, two procedures are considered to obtain functions relating the peak ground acceleration to the maximum spectral displacements. The first method is based on a series of non-linear dynamic analyses, while the second is based on the well-known ATC-40 procedure called equal displacement approximation. After applying both procedures, the probability density functions of the maximum displacement at the roof of the building are gathered and compared. The expected structural damage is finally obtained by replacing the spectral displacement calculated using ATC-40 and the incremental dynamic procedure. In the damage functions, the results obtained from incremental static and dynamic analyses are compared and discussed from a probabilistic point of view.