PROBABILISTIC OPTIMAL DESIGN OF PASSIVE CONTROL DEVICES COHERENTLY WITH SEISMIC CODES RESPONSE SPECTRA

Passive control devices are widely used to improve the response of structures subjected to dynamic loadings, like earthquakes and wind. Although the uncertainty present in the loads is well-known, seismic codes often suggest simplified approaches for the design of device properties in which the response dispersion due to these uncertainties is neglected, and the attention is focused on the mean response only. In this study, a procedure for the optimal design of nonlinear viscous dampers is proposed into a stochastic framework. The procedure consists in an outer loop in which the optimal pattern of damper parameters is evaluated by minimizing an objective function related to the dampers cost and subjected to a constraint on the structural behaviour. For each damper configuration, the response of the structure is fully characterized in a probabilistic sense by means of stochastic analysis. Aiming at this, it is firstly assumed that earthquake loads can be represented by a stationary stochastic process, fully defined by its Power Spectral Density (PSD) function. In this application, an analytic model provides closed-form PSD functions coherent to Response Spectra suggested by seismic codes. Numerical applications have been carried out with two different Multi-Degree-Of-Freedom (MDOF) structures in order to assess the validity of the proposed approach and its applicability to the design of passive control devices coherently with the provisions of seismic building codes.