Seismic fragility analysis of a reinforced concrete building under different natural ground motions

Fragility curves indicate the probability of structural damage caused by earthquakes as a function of ground motion indices such as peak ground acceleration (PGA), peak ground velocity (PGV), spectral acceleration (Sa), and spectral displacement (Sd). This study examines the fragility curves of a reinforced concrete building subjected to different natural ground motions. For this purpose, a representative high-rise reinforced concrete building located in Istanbul was selected. In order to assess the seismic performance of the existing building, some natural earthquake records with different characteristics were used. The ground motion records were classified according to their PGA to PGV ratios (a/v ratios). Based on a/v ratio, three sets of natural ground motions were considered i.e. low, intermediate, and high. Then, nonlinear time history analyses were carried out to provide the structural response of the existing building. Using a probabilistic seismic demand model obtained by regression analysis on the simulated damage data, the individual fragility curves for slight, moderate, major, and collapse damage states were constructed. Thus, the fragility curves of the existing building were achieved for three different classifications of a/v ratio. As a result, it was observed that the variations in the characteristic of the ground motion had pronounced effect on the developed fragility curves (or probability of vulnerability) of the building.