Seismic assessment for typical soft-storey reinforced concrete structures in Bucharest, Romania

In this study, a seismic assessment is performed for a low-code high-rise soft-storey reinforced concrete (RC) structure typical for Bucharest, Romania. One such RC structure collapsed in Bucharest during the March 1977 Vrancea intermediate-depth earthquake. Most of these structures were not retrofitted after the 1977 seismic event, they have been poorly maintained and have been affected by two additional Vrancea seismic events in 1986 and 1990. As such, considering that they are still inhabited by many Bucharest residents, the seismic assessment of these structures is an urgent matter. Consequently, a fragility analysis based on the results of typical pushover analyses, as well as based on incremental dynamic analyses is performed firstly. Moreover, a detailed sectional analysis regarding the seismic capacity of the vertical structural elements situated at the ground storey is also performed and highlights the brittle seismic behaviour of many RC vertical structural elements. The analyses also show that the structure has a larger strength in the transversal direction, but the displacement capacity is about half that for the longitudinal direction. Finally, the mean annual collapse probabilities computed using the ground motions from a Monte-Carlo simulated earthquake catalogue for the Vrancea intermediate-depth seismic source have the same order of magnitude on both principal directions of the structure, an observation confirmed by damage data collected after the 1977 Vrancea earthquake.