Characterization of ground motion intensity for the seismic fragility assessment of plan-irregular RC buildings

Bhasker, Rohan; Menon, Arun

doi:10.1016/j.istruc.2020.08.019

Cited by 16 publications

(6 citation statements)

References 39 publications

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“…The efficiency of a given IM in predicting the maximum interstorey drift demands (θ max ) on the test structure is determined by cloud analysis using the suite of fifty ground motion records. In the present study, the widely adopted log-linear model (Equation 1) for seismic demand [25,8] is used to represent the functional relationship between the predictor variable (IM) and the response variable (θ max ).…”

Section: Efficiency Analysismentioning

confidence: 99%

“…The larger the size of the bin, the more time consuming will be the execution of NLRHA. The current study builds on the understanding that certain intensity measures are more efficient than others [7,8] and seeks to examine whether the choice of IM has a bearing on the minimum number of records necessary to accurately calibrate a demand model for cloud analysis. If so, the assessment framework could clearly benefit from the use of highly efficient IMs in formulating the demand model.…”

Section: Introductionmentioning

confidence: 99%

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On the choice of ground motion intensity measure and the number of records for cloud analysis-based seismic demand assessment

Bhasker¹,

Menon²

2022

ASPS Conf. Proc.

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Cloud analysis has emerged as a popular tool for the seismic demand/fragility assessment of structures. The output of cloud analysis is a seismic demand model which relates an Engineering Demand Parameter (EDP) indicative of structural distress to an Intensity Measure (IM) signifying the severity of ground shaking. IMs commonly used for probabilistic seismic demand assessment are quite heterogenous with respect to their “efficiency”, i.e. their degree of correlation with a specific EDP. This feature has serious implications on the number of ground motion records that must be used to perform cloud analysis on a given structure in order to accurately describe the distribution of the EDP at various IM levels. In the current study, demand models for maximum interstorey drift (?max), based on a wide spectrum of IMs, are developed from the cloud analyses of a five-storey RC bare frame structure using a suite of fifty unscaled natural ground motion records. The method of bootstrap resampling is used to investigate the convergence of the regression coefficients in the demand model with the size of the bootstrap subsamples, each comprising of a limited subset of records drawn from the original suite with repetitions allowed. This procedure helps determine the minimum number of ground motion records necessary for the calibration of demand models without compromising its accuracy in predicting the drift demands. Results from the study indicate a strong correlation between the efficiency of various IMs and the optimal number of records required to produce reliable seismic demand models.

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Section: Efficiency Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

On the choice of ground motion intensity measure and the number of records for cloud analysis-based seismic demand assessment

Bhasker¹,

Menon²

2022

ASPS Conf. Proc.

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“…56 In recent years, researchers have explored the optimality of this measure in quantifying the seismic demands on planirregular systems subjected to bi-directional seismic action. 25,59 Bhasker and Menon, 60 through a cloud analysis-driven investigation on a low-rise non-ductile building, identified 'average spectral acceleration (Sa avg )' defined by Equation ( 5…”

Section: Choice Of Ground Motion Immentioning

confidence: 99%

“…74,76,77 Numerous studies have demonstrated Sa avg , the IM used in this study, to be a more efficient descriptor of ground shaking severity compared to popular measures such as the first mode spectral acceleration (Sa(T 1 )), peak ground velocity (PGV), peak ground acceleration (PGA) and so forth. 56,59,60 Several investigations that used Sa(T 1 ) as the IM, have successfully defined the distribution of structural responses employing as few as 20 ground-motion records. 76,78,79 Taking note of the higher efficiency of Sa avg compared to Sa(T 1 ), it seems fairly justified to limit the size of the ground-motion record ensemble used in the current investigation to twenty.…”

Section: Ground-motion Recordsmentioning

confidence: 99%

A seismic fragility model accounting for torsional irregularity in low‐rise non‐ductile RC moment‐resisting frames

Bhasker

Menon

2021

Earthq Engng Struct Dyn

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Buildings characterized by torsional irregularity are notorious for their vulnerability to earthquakes. However, most fragility/vulnerability models used for regional seismic risk assessment fail to distinguish between buildings with torsionally balanced and unbalanced configurations. The present study aims to develop a seismic fragility model sensitive to torsional irregularity for low-rise non-ductile RC moment frame buildings. To this end, a numerical investigation centred on 13 three-storied plan-asymmetric models, each characterized by a distinct combination of normalized stiffness eccentricity, torsional radius to mass radius of gyration ratio and normalized strength eccentricity, is presented. Using high-dimensional model representation (HDMR), a metamodel for the maximum inter-storey drift under bi-directional seismic action is calibrated, considering average spectral acceleration and the above trio of torsional irregularity descriptors (TIDs) as the predictor variables. Carrying out numerical simulations on limit state functions formulated using the above demand model and appropriate capacity thresholds, the seismic fragility is estimated. The parameters of a lognormal fragility function compatible with the above estimates are determined using the method of maximum likelihood. A strong correlation is observed between the TIDs and the fragility function parameters. This reinforces the importance of accounting for all three TIDs while rating the seismic fragility of a building. Using least-square error minimization technique, a functional relationship is established between the fragility model parameters and the TIDs. The framework described herein provides a simple, yet rational means to develop the next generation of seismic fragility models accounting for one of the most critical factors governing seismic behaviour--'torsional irregularity'.

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“…P. Giannakouras, C. Zeris [21] performed the pushover analysis and nonlinear time history analysis with the direct displacement-based seismic design (DDBD) method in the vertically irregular structure to study the performance of the structures. To understand the seismic performance of the irregular structure, the pushover and nonlinear time history analysis help better than linear analysis and it also helps to prevent failure [22], [23].…”

Section: Introductionmentioning

confidence: 99%

Effect of position of steel bracing in L-shape reinforced concrete buildings under lateral loading

Bohara¹,

Ganaie²,

Saha³

2021

Res. Eng. Struct. Mater.

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The level of damage in irregular structures is more compared to regular structures. In this study, L shaped RC buildings are investigated with and without steel bracings in different positions in frames. The response spectrum analysis has been done by using ETABs software. The two cases considered, case I and case II for understanding the effect in inverted V bracing in L shape building. Case II shows the suitable seismic parameters when bracing is used properly. Interstory drift, displacements, base shear, fundamental time period, torsional irregularity ratio and the capacity ratio of the columns are evaluated. It is also noticed that adding the steel bracing decreases the inter-story drift, displacements of the structure effectively. The torsional irregularity ratio of each 12 models are studied carefully. The capacity ratio of the selected columns is studied to understand the performance of the columns while using the steel bracing in the buildings. The steel bracings are effectively used as retrofitting in L shaped buildings if the position of bracings are considered in the frames appropriately. While designing irregular buildings with steel bracings, the torsional effect should be checked.

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Characterization of ground motion intensity for the seismic fragility assessment of plan-irregular RC buildings

Cited by 16 publications

References 39 publications

On the choice of ground motion intensity measure and the number of records for cloud analysis-based seismic demand assessment

On the choice of ground motion intensity measure and the number of records for cloud analysis-based seismic demand assessment

A seismic fragility model accounting for torsional irregularity in low‐rise non‐ductile RC moment‐resisting frames

Effect of position of steel bracing in L-shape reinforced concrete buildings under lateral loading

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