SEISMIC PERFORMANCE-BASED RELIABILITY OF BUILDING STRUCTURES (original) (raw)
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Journal of Earthquake Engineering, 2014
A probabilistic methodology is proposed for the seismic performance analysis of existing buildings using global metrics to determine if the behavior conforms to a given limit state. The referred performance metrics are the mean annual frequency of the limit state, the corresponding expected loss associated to the repair of the building, and the corresponding number and type of mechanisms that occur. The consideration of these assessment parameters to control building performance widens the scope of the limit state definitions proposed in current codes. Therefore, current limit state descriptions were updated to establish adequate risk-and cost-related limit state definitions using the Eurocode 8 Part 3 proposals as a basis for discussion. The description of the proposed procedure is detailed and addresses its applicability for different limit states and its ability to include the uncertainty in the limit state capacities. An application involving the performance analysis of a reinforced concrete structure for several limit states is also presented and discussed.
Probability-Based Seismic Performance Evaluation for Buildings
World Journal of Engineering and Technology, 2016
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.
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A seismic performance evaluation is one of the highly complicated multi-criteria evaluation problems. This study presents a hierarchy of performance criteria that consists of performance categories such as strength, stiffness, configuration, and age of structures at a higher level while their subcategories considering the capacity of subsystems and components at lower levels mainly focus on the stage of preliminary evaluation. Two methods for determination of performance index are proposed; a simple composition method and a fuzzy inference method. Both methods use weighting factors to represent relative importance of multi-criteria in the determination of performance index. The simple composition method that operates on definite index values and assumes independence between performance criteria is easy to use but difficult to address the cases where complicity and uncertainty are of important problems. The fuzzy inference system uses fuzzy concepts where uncertainties are inherently unavoidable due to insufficient information and engineering assumption and exploits fuzzy rules in the multi-criteria evaluation by replicating heuristic knowledge and experience in logic-based descriptive rules. Moreover, the single performance index obtained by defuzzification enables us to draw a representative and comprehensive seismic performance index from a set of individual performance indexes at multi-levels.
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Civil Engineering and Architecture, 2022
The probability of failure associated with drift criterion exceeding certain performance levels for the intensity of earthquake record ground motions has been necessitated for the development of fragility curves in the recent past as a better performance check tool. In the recent past, the reappraisal of fragility curves formation due to incremental dynamic analysis has been possible because of modeling and simulation of structures under varying earthquake ground motions. The content of this paper is the formation of fragility curves using drift as the output of steel building frames under varying earthquake ground motions. The fragility curves were developed through nonlinear time-history analysis assessments of selected ground vibrations with varying magnitudes, distances from the source, and site circumstances. The entire process given in this paper can be utilized to develop probabilistic fragility curves for structural buildings of various layouts. As an illustration, fragility curves for two steel building structures for various performance levels: Collapse prevention (CP), Life Safety (LS), Immediate occupancy IO), & operational performance (OP), were developed using Ram Perform 3D, using a set of 20 earthquake ground motions. The fragility curves formed using drift for different performance levels reveal a robust damage index for evaluating building structures under the high level of seismic hazards.
Reliability of Seismic Performance Assessments for Individual Buildings and Portfolios
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Seismic performance and loss assessments are required in areas of Insurance, Finance and Public Policy. Providers are Structural Engineers and Risk Management Firms. There are no current procedures to evaluate the epistemic and aleatory uncertainties for such assessments. The essential issue is whether or not there is sufficient reliability in the result to use the result as the basis for risk management decisions and actions. For a single building this may be whether or not a prescribed earthquake performance level is met, life safety or if a portfolio’s vulnerability level is acceptable, whether the. loss for a given time period is less than a stated value. A method based in part on Federal Emergency Management Agency P-695, is developed for evaluating the reliability of performance and/or loss assessments for both individual and portfolios of buildings. Consideration is given to how well the building investigation and corresponding evaluation process have been performed, the qual...
Uncertainty and Fuzzy Decisions in Earthquake Risk Evaluation of Buildings
Engineering Journal, 2019
The Northern region of Thailand has been considered as one of the seismic risk zones. However, most existing buildings in the area had been designed and constructed based on old building design codes without seismic consideration. Therefore, those buildings are required to upgrade based on earthquake building damage risk evaluation. With resource limitations, it is not feasible to retrofit all buildings in a short period. In addition, the results of the risk evaluation contain uncertain inputs and outputs. The objective of this study is to prioritize building retrofit based on fuzzy earthquake risk assessment. The risk assessment of a building was made considering the risk factors including (1) building vulnerability, (2) seismic intensity and (3) building values. Then, the total risk was calculated by integrating all the risk factors with their uncertainties using a fuzzy rule based model. An example of the retrofit prioritization is shown here considering the three fuzzy factors. The ranking is hospital, temple, school, government building, factory and house, respectively. The result helps decision makers to screen and prioritize the building retrofitting in the seismically prone area.
Seismic Performance Based Loss Assessment
Proceedings of the 13th …, 2004
The paper describes procedures adopted to develop and implement building vulnerability curves to relate damage ratio (defined as dollar loss / replacement value) to spectral acceleration for individual building and portfolio loss assessment. The Performance Based Engineering ...
Engineering Structures, 2019
The probabilistic seismic hazard analysis (PSHA), is currently one of the most used approaches worldwide for assessing seismic hazard, and represents the mostly used approach adopted for the development of seismic maps. PSHA relies on strong mathematical bases, and it is a correct application of the Total Probability Theorem; it is thus able to combine three main sources of uncertainty, e.g. the earthquake magnitude, the source-to-site distance and the corresponding ground-shaking scenario. As a consequence, because of its intrinsic nature, also model parameters can be sources of variability, since most of the time they are extrapolated from historical data. Thus, this work wants to give a contribution on the debated problem of uncertainty in seismic hazard estimates, by proposing a semi-analytical formulation able to include uncertainties arising from model parameters, treating them, in turn, as random variables. The proposed formulation adopts the reliability index and its standard deviation for computing hazard curves characterized by an assumed probability to be underestimated. In the second part of the work, the formulation is applied to a case study represented by an existing bridge, showing its practical use and investigating how different levels of knowledge of seismic hazard model input parameters, can impact the outcomes of a classical structural seismic reliability or risk analysis carried out without taking into account such specific issue.
Reliability analysis of uncertain structures using earthquake response spectra
This paper develops a probabilistic methodology for the seismic reliability analysis of structures with random properties. The earthquake loading is assumed to be described in terms of response spectra. The proposed methodology takes advantage of the response spectra and thus does not require explicit dynamic analysis of the actual structure. Uncertainties in the structural properties (e.g. member cross-sections, modulus of elasticity, member strengths, mass and damping) as well as in the seismic load (due to uncertainty associated with the earthquake load specification) are considered. The structural reliability is estimated by determining the failure probability or the reliability index associated with a performance function that defines safe and unsafe domains. The structural failure is estimated using a performance function that evaluates whether the maximum displacement has been exceeded. Numerical illustrations of reliability analysis of elastic and elastic-plastic single-story frame structures are presented first. The extension of the proposed method to elastic multi-degree-of-freedom uncertain structures is also studied and a solved example is provided.