Reliability-based Sensitivity Analysis of Shear Frame Equipped with Nonlinear Viscous Damper

Recently, nonlinear viscous dampers have been widely used to improve the seismic performance of structures. These dampers dissipate the kinetic energy caused by the earthquake by producing a damping force. These dampers are designed in such a way that the force is proportional to the velocity. The Maxwell model is the most common model for modeling the behavior of nonlinear viscous dampers. In this model, the damping coefficient, the velocity exponent and the axial stiffness of the dampers are the key parameters. In most previous studies, the uncertainty of the underlying parameters in behaviour of viscous dampers has been ignored while it can has a significant effect on the seismic response of structures. In this study, first, the reliability analysis of a shear frame equipped with a nonlinear viscous damper was performed using the Monte Carlo sampling method. The results show that increasing the maximum drift from 0.015 to 0.02 reduces the probability of failure by 72%. Then, reliability-based sensitivity analysis of the studied frame was performed in order to determine the most effective random variable on the reliability of the frame. The results show that the velocity exponent is the most effective random variable on the reliability of the frame. Also, results indicate that importance of random variables depends on the used limit state function in the reliability analysis. For example, the imporatance value of the damping coefficient is 59% and 9.5% less than the velocity exponent with respect to the maximum drift of 0.015 and 0.025, respectively.