ANALYSIS OF THE INFLUENCE OF VISCOUS DAMPERS PROPERTIES VARIABILITY VIA RELIABILITY-BASED OPTIMIZATION METHOD

The response of viscous devices is notably influenced by the values assumed by the two consti-tutive parameters governing the damper behaviour, namely: the viscous coefficient c and ve-locity exponent . At this regard, devices manufacturing process may introduce some level of variability on the expected nominal values of c and . In order to control the damper response deviation from the nominal conditions, the main international codes provide some acceptance tolerance criteria to be checked during prototype tests. However, no admissible ranges of var-iability are directly specified for the damper constitutive parameters. In light of this, the aim of this study is that of analyzing the sensitivity of the seismic risk of structural systems with respect to uncertain damper properties, in order to assess the effectiveness of the tolerance criteria provided by the international seismic regulations in controlling the structural performance pa-rameters variation. An innovative approach [1] based on the solution of a reliability-based optimization (RBO) problem is used, in which the optimization is carried out to search for the worst combination of the uncertain damper parameters, within the allowed range of variation, that maximize a probabilistic objective function expressing the variation of the mean annual frequency of exceedance of some relevant performance demand thresholds. A moment resisting steel building with linear and nonlinear viscous dampers is analysed. The study results show that the considered source of variability can have non-negligible effects on the structural seis-mic response, with some EDPs showing higher sensitivity than others. Keywords: