Correlation between the probabilistic seismic asssment of frame structures without and with added dampers

This paper deals with the parameters which influence the probability of reaching the near collapse limit state of RC frame structures equipped with nonlinear fluid viscous dampers. The study can be divided into two steps. The first aims to assess how the median and the dispersion of seismic demand can vary in the RC frame structures equipped with nonlinear fluid viscous dampers, considering a wide set of ground motions; these parameters have been compared with those obtained for RC structures without dampers. The second step evaluates the expression in closed form given in the 2000 SAC/FEMA method to assess the annual probability of failure of RC structures. This calculation has been performed using the parameters obtained in the previous step. The annual probability of failure has been estimated for the RC frame structures with and without dampers, considering a wide set of ground motions and different method to approximate the hazard curve. The adopted case study is a frame configuration characterized by three bays and six floors. The analyses have allowed to evaluate the variability of the terms of the closed form expression proposed in the 2000 SAC/FEMA method, and their influence on the definition of the annual probability of failure.