Preliminary Investigation on Selecting Optimal Intensity Measures for Simplified Fragility Analysis of Mid-Rise RC Buildings (original) (raw)
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Engineering Structures, 2016
This paper presents a new approach for the derivation of fragility curves, named FRAgility through Capacity spectrum ASsessment (FRACAS). FRACAS adapts the capacity spectrum assessment method and uses inelastic response spectra derived from earthquake ground motion accelerograms to construct fragility curves. Following a description of the FRACAS approach, the paper compares the predicted maximum interstory drift (MIDR) response obtained from FRACAS and nonlinear time history analyses (NLTHA) for two case-study buildings subjected to 150 natural accelerograms. FRACAS is seen to represent well the response of both case-study structures when compared to NLTHA. Observations are made as to the sensitivity of the derived fragility curves to assumptions in the capacity spectrum assessment and fragility curve statistical model fitting. The paper also demonstrates the ability of FRACAS to capture inelastic record-to-record variability and to properly translate this into the resulting fragility curves.
Uncertainty in Seismic Intensity Measures Used for Fragility Analysis
Proceedings of the 6th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2015), 2017
Seismic fragility is the main tool used in the performance-based earthquake engineering, and represents the probability of a dynamic system to enter a damage state for a given intensity measure (IM). The most commonly-used seismic IMs are the peak ground acceleration (P GA), which is the absolute maximum of the ground acceleration, and the spectral acceleration (SA), which characterizes well the response of simple linear systems, but shows large uncertainties in the characterization of the seismic response of complex non-linear systems. The main assumption that underlies the basis of the selection of P GA or SA as IMs is that they correlate satisfactorily with the demand parameters (D) of realistic structures, i.e., nonlinear, complex dynamic systems. Statistics and tools of random vibrations are employed to quantify the dependence relations between seismic IMs and structural demand parameters, for non-linear systems subjected to seismic ground-motion records.
2021
This paper focuses on the probabilistic analysis of Intensity Measures (IMs) and Engineering Demand Parameters (EDPs) for earthquake excitations. Several statistical properties, which are desirable in IMs when they are used to predict EDPs, have been analyzed. The main sources of uncertainty involved in the calculation of the seismic risk have been considered in the analysis. Efficiency, sufficiency and steadfastness have been quantified for a set of IMs with respect to two EDPs: the maximum inter-storey drift ratio, MIDR, and the maximum floor acceleration, MFA. Steadfastness is a new statistical property proposed in this article. It is related to the ability of IMs to forecast EDPs for big building suites. This also means that efficiency does not significantly vary when different types of buildings are included in the statistical analyses. This property allows reducing the number of calculations when performing seismic risk estimations at urban level since, for instance, a large v...
An approximate procedure for estimating seismic demands for buildings
MATEC Web of Conferences
Methods of the estimation of the seismic demands of nonlinear structures require a sort of iterative procedures, no matter the elastic or inelastic response spectra are used in the procedure. Many studies dealt with the development of different inelastic spectra with the aim to simplify the evaluation of inelastic deformations and performance of structures. Recently, the concept of inelastic spectra has been adopted in the global scheme of the performance-based seismic design through capacityspectrum methods (CSM).For instance, the modal pushover analysis (MPA) has been proved to provide accurate results for inelastic buildings to a similar degree of accuracy to the response spectrum analysis (RSA) in estimating peak response for elastic buildings. In this paper, a simplified nonlinear spectral analysis is made to the original MPA is proposed. The proposed procedure, which is applicable to multi-degree-of-freedom MDOF systems uses an inelastic spectrum and gives peak responses consistent with those obtained when using the nonlinear time history analysis (NL-RHA).The accuracy of the proposed procedure is verified against the nonlinear time history analysis results of two buildings. The comparison showed that the new method is capable to provide accurate peak response.
Development of analytical seismic fragility functions for the common buildings in Iran
Bulletin of Earthquake Engineering
One of the main components for the development of regional seismic risk models is the fragility functions for common building types. Due to the differences between the national design codes, construction practices, and construction materials, it is necessary to develop speci c fragility functions for the common building types which are constructed in each region. One of the existing challenges is the lack of classi ed, reliable, and cogent local seismic fragility functions for common buildings in Iran. For this reason, the present study is devoted to lling this essential gap. Therefore, at the rst step, a comprehensive study was performed on the existing building types in the country. Finally, the Iranian common buildings are classi ed into 35 categories regarding material, lateral-loadresisting system, age, height, and code level. Also, by conducting comprehensive studies on all previously performed researches in the country, structural and dynamic parameters have been collected for buildings in each class. This information was used to compute a large set of backbone curves for Iranian buildings taxonomy. In the next steps, a large set of ground motion records were selected. Then non-linear time-history analyses were performed on the generic backbone curve for each type of building, and the structural responses were used to derive fragility functions for building classes. Then nearly three hundred appropriate fragility functions were generated for Iranian common buildings considering both record-to-record and building-to-building response variability using cloud analysis. Based on the existing empirical data from past earthquakes in the country, the validation of the resulting fragility functions was carried out. The resulted fragility functions can be utilized in seismic risk assessment studies in the country.
Soil Dynamics and Earthquake Engineering, 2019
This paper deals with the selection of optimal intensity measures (IMs) for displacement-based seismic demand assessment and fragility derivation of case-study mid-rise reinforced concrete (RC) frames. The considered frames represent distinct RC vulnerability classes in the Mediterranean region. Optimal IM selection is performed by means of probabilistic seismic demand models considering multiple IMs and various engineering demand parameters (EDPs). Based on findings from previous and concurrent studies, a small subset of potential IMs is investigated here, including conventional peak IMs and two advanced scalar IMs accounting for spectral shape over a range of periods. Probabilistic seismic demand models are built on data obtained from analysis of the casestudy frames subjected to over nine hundred ground motions by employing an innovative capacity spectrum method using inelastic response spectra derived from actual earthquake accelerograms to estimate seismic demand and derive fragility curves. This approach has the advantage of simplicity and rapidity over other methods as nonlinear dynamic analysis. This study concludes that advanced IMs, and particularly the ones accounting for the period elongation (due to the nonlinear structural behavior) and structure-specific parameters, can effectively satisfy all the selection criteria, including the hazard computability criterion.
Spectral shape proxies and simplified fragility analysis of mid-rise reinforced concrete buildings
2015
The objective of this study is to identify an optimal intensity measure (IM) for conditioning probabilistic seismic demands of case-study reinforced concrete (RC) frame buildings, representative of mid-rise RC building classes in the Mediterranean region. The prediction is performed via statistical relationship between multiple IMs (particularly advanced scalar parameters accounting for spectral shape over a range of periods) and various displacement-based engineering demand parameters (EDPs). Such statistical relationships are built on data obtained from analysis of the frames subjected to over nine hundred ground motion records by employing an innovative capacity spectrum method, introduced in the paper, which uses inelastic response spectra derived from actual earthquake accelerograms to estimate seismic demand and derive fragility curves. The outcomes of the present work are in a good agreement with previous investigations conducted by other researchers on selecting optimal IMs ...
Guesstimation of Seismic Fragility in Structural Systems
International Journal of Computing, Intelligent and Communication Technology
Dynamic analysis is used to estimate fragility functions, and is an essential part of a number of seismic measurement procedures. This paper investigates the applicability of statistical inference methods for the prediction of fragility functions, outlines useful methods for use in various structural analysis techniques, and investigates how fragility functions can be updated to minimize the number of structural analyses needed. Multiple stripe method is more effective fragility projections for a provided variety of structural analysis than IDA, meaning that some understanding of the building's capacity is needed prior to analysis such that sufficient portions of the fragility curve can be loosely described This discovery has alternative blessings, because the approach to multiple stripe analysis permits numerous ground movements to be used for studies at totally different intensity ranges to replicate the various options of low intensity and trembling of high intensity. The pro...
Assessing Seismic Fragility of Low-Rise RC Buildings by means of Incremental Dynamic Analysis (IDA)
2022
The modern era witnessed an urbanization and economic growth concentrated in urban areas. Despite an increase in welfare, this receives a greater threat when an earthquake occurs. This research aims to assess the structural risk of low to medium-rise reinforced concrete building structures, commonly built in developing countries. This research was carried out by performing an incremental dynamic analysis (IDA) od an existing building model. In this analysis, the structural model was given a set of dynamic earthquake loads which were increased in magnitude according to certain scale rules until the structure experienced nonlinear behavior and reached a near collapse condition. Five artificial accelerogram recordings were applied on the structure after matching with the spectral response of the target location of the structure. From the analysis, the IDA curves were obtained which describes the global dynamic behavior of the structure, namely displacement due to earthquake lateral loads. Then the damage limits were determined on the IDA curve based on the HAZUS criteria. Then the seismic risk was expressed by constructing a seismic fragility curve. This curve states the probability of exceeding certain damage limits due to variation in earthquake intensity during the service life of the structure.