Multi-objective optimal design of semi-active fluid viscous dampers for nonlinear structures using NSGA-II

Abstract

This paper presents an effective method to design semi-active fluid viscous damper (SAFVD) system for mitigating the seismic responses of the nonlinear frames considering multiple safety and convenience criteria. This method is based on defining a multi-objective optimization problem with discrete objective functions of minimization of inter-story drift as safety criterion as well as absolute acceleration as convenience criterion where an improved version of the non-dominated sorting genetic algorithm (NSGA-II) has been used to solve it and find out the Pareto-optimal solutions. For this purpose, the maximum damping coefficient of the semi-active damper and parameters of the control algorithm have been selected as design variables. The effect of the uncertainty of the input seismic excitation has been considered using the mean responses under multiple real earthquakes recommended for the site that the structure is located in. To assess the effectiveness of the proposed methodology, a numerical example has been conducted on an eight-story nonlinear shear building frame with hysteretic bilinear elasto-plastic behavior. The results show that the designed optimal SAFVD system has the capability of a significant reduction in seismic responses and improving both the safety and convenience of the entire building. Also comparing the seismic performance of SAFVD system with that of active control system shows that SAFVD could perform as effective as active control system in structural response mitigation.