787 Copyright © 2015, IGI Global. Copying or distributing in print or electronic forms without written permission of IGI Global is prohibited. Chapter 35 DOI: 10.4018/978-1-4666-7456-1.ch035 Multi-Objective Optimization Design of Control Devices to Suppress Tall Buildings Vibrations against Earthquake Excitations Using Fuzzy Logic and Genetic Algorithms ABSTRACT The main objective of this chapter is to fnd the optimal values of the parameters of the base isolation systems and that of the semi-active viscous dampers using genetic algorithms (GAs) and fuzzy logic in order to simultaneously minimize the buildings’ selected responses such as displacement of the top story, base shear, and so on. In this study, performance of base isolation systems, and semi-active vis- cous dampers are studied separately as diferent vibration control strategies. In order to simultaneously minimize the objective functions, a fast and elitist non-dominated sorting genetic algorithm (NSGA-II) approach is used to fnd a set of Pareto-optimal solution. To study the performance of semi-active viscous dampers, the torsional efects exist in the building due to irregularities, and unsymmetrical placement of the dampers is taken into account through 3D modeling of the building. INTRODUCTION One of the most important tasks in structural engineering is to reasonably minimize the un- desired vibrations of the structures due to the environmental dynamic loads such as earthquake excitations. Various strategies and theories have been investigated and developed to approach this goal over the years. Use of the control systems is one of these methods to enhance the structural Saeid Pourzeynali University of Guilan, Iran Shide Salimi University of Mohaghegh-Ardebili, Iran