Stochastic response of nonlinear base isolation systems

Abstract

A hybrid base isolation system was used to retrofit two residential buildings in Solarino, Sicily. Subsequently, five free vibration tests were carried out in one of these buildings to assess its functionality. The hybrid base isolation system combined high damping rubber bearings with low friction sliders. In terms of numerical modeling, a single-degree-of-freedom system is used here with a new five-parameter trilinear hysteretic model for the simulation of the high damping rubber bearing, coupled with a Coulomb friction model for the simulation of the low friction sliders. Next, experimentally obtained data from the five free vibration tests were used for the calibration of this six parameter model. Following up on the model development, the present study employs Monte-Carlo simulations in order to investigate the effect of the unavoidable variation in the values of the six-parameter model on the response of the base isolation system. The calibrated parameters values from all the experiments are used as mean values, while the standard deviation for each parameter is deduced from the identification tests employing best-fit optimization for each experiment separately. The results show that variation in the material parameters of the base isolation system produce a nonstationary effect in the response. In addition, there is a magnification effect, since the coefficient of variation of the response, for most of the parameters, is larger than the coefficient of variation in the parameter values.