Ground Motion Recording-Based Validation of Capacity Curves for High-Rise Reinforced Concrete Structures in Romania Constructed Before 1977

Capacity curves are essential in the evaluation of seismic fragility of structures and especially in seismic risk assessments. The most widely used approach for evaluating capacity curves is based on static nonlinear analyses performed in dedicated software. However, a validation of such curves is necessary considering the uncertainties associated with the analyses. Overall, 18% of the population of Romania that lives in reinforced concrete buildings inhabits high-rise structures. In Bucharest, the percentage of people living in the same category of structures is more than 40%. A large part of these structures was built before the Vrancea 1977 earthquake. In this context, this paper presents a review of existing capacity curves for this category of high-rise reinforced concrete structures in Romania. Next, an analysis of relevant ground motions recorded on buildings during various Vrancea intermediate-depth earthquakes (1986 and 1990) is performed. In addition, results from various ambient vibration measurements are also used for a more thorough understanding of the dynamic characteristics of the buildings and of their stiffness. A comparison between the analytical capacity curves and the data from ground motion recordings is presented, highlighting significant differences, especially for reinforced concrete frame structures. Finally, updated capacity curves for high-rise residential structures constructed before 1977 are proposed by combining the analytical results with the earthquake data.

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