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A control algorithm combining viscous and non-linear Reid damping mechanisms has beenrecently proposed by the authors to command active friction dampers. In this paper, friction dampers andthe proposed algorithm are applied to control the seismic responses of a nonlinear 20-story building.Piezoelectric stack actuators are used to implement the control algorithm. The capacity of each damper isdetermined by the practical size of piezoelectric actuators and the availability of power supply. Thesaturation effect of the actuators on the building responses is investigated. To minimize the peak storydrift ratio or floor acceleration of the building structure, a practical sequential procedure is developed tosub-optimally place the dampers on various flors. The effectiveness of active friction dampers and theefficiency of the proposed sequential procedure are verified by subjecting the building structure to fourearthquakes of various intensities. The performance of 80 dampers and 137 dampers installed on thestructure is evaluated according to 5 criteria. Numerical simulations indicated that the proposed controlalgorithm effectively reduces the seismic responses of the uncontroled 20-story building, such as inelasticdeformation. The sub-optimal placement of dampers based on peak acceleration outperforms that based onpeak drift ratio for structures subjected to near-fault ground motions. Saturation of piezoelectric actuatorshas adverse effect on floor acceleration.