SIMPLIFIED RELIABILITY ASSESSMENT OF RC FRAMES EQUIPPED WITH VISCOUS DAMPERS

The object of this paper is the study of simplified probabilistic procedures for the seismic assessment of nonlinear structures equipped with nonlinear fluid viscous dampers. The considered reference probabilistic approach is the 2000 SAC-FEMA method, which allows to obtain the probability of exceeding a specified performance level. In particular the purpose is to study the correlation between the results of the probabilistic seismic assessment method for structures without and with dampers, with emphasis on the results in terms of dispersion. To this aim a wide set of recorded ground motions has been selected and applied to the considered RC frames. The study has been performed without applying scaling factors to the earthquake records, but selecting different sets of records for increasing values of seismic intensity. All the obtained results have been examined considering different criteria for the determination of the set of time-history analyses to be used for the probabilistic evaluation and different methods to obtain the dispersion of seismic demand. Moreover, with reference to the application of the SAC-FEMA method, a sensitivity analysis has been performed considering different procedures for the interpolation of the hazard curve. From the analyses it has been possible to derive expressions to correlate the results for structure without and with dampers and suggestions for the application of the SAC-FEMA method. Finally, a direct procedure previously proposed by some of the authors for the response assessment of nonlinear structures with nonlinear viscous dampers has been applied for the probabilistic assessment of the case study as an alternative to nonlinear dynamic analyses.