Seismic Fragility Assessment of Existing 9 Storey Reinforced Concrete (RC) Buildings in Patna, India

Abstract

AbstractPrecise and accurate estimation of building’s response is the demand of the time. Since the response of any building is always associated with inherent uncertainty, its consideration is utmost for the preciseness of their vulnerability. The uncertainties can be due to two reasons, (1) randomness in ground motion, also termed as aleatoric uncertainty, and (2) variability in structural modelling (epistemic uncertainty). The present work focuses on obtaining the variability functions and fragility curves by considering those uncertainties for 9 storey RC buildings in Patna, India, which is a region of high seismicity. Variability due to randomness in ground motion was determined by generating several artificial ground motions (comprising both near as well as far-field). Therefore, extensive study of the seismotectonic map of the region was required to determine the nearby faults, past earthquakes and other random parameters contributing variability. Structural variability, on the other hand, is generally attributed to the uncertainty in the estimation of material, geometrical properties, of which the building is made and at the same time due to the uncertainty in design details. Therefore, their consideration is vital in fragility analysis. Material strength, storey height, plan typology and design methodologies were considered as the random parameters in this study. The selection of these parameters was purely based on the extensive survey of buildings in the region. Considering the several combinations of random parameters, the buildings were analysed using non-linear static (NLS) pushover analysis to obtain pushover curves. These pushover curves were converted to capacity curves considering the dynamic characteristic of the first mode of vibration. The obtained capacity curves were then utilised to derive the variability in the capacity spectrum corresponding to particular damage states. Eventually, lognormal variability function and fragility curves for 9 storey representative buildings were obtained considering both the uncertainties. The obtained fragility curves corresponding to particular damage states give a measure for the vulnerability of buildings in that region.KeywordsAleatory and epistemic uncertaintyCapacity spectrumGround motionPushover analysisVariability functionFragility curveVulnerability assessment