The structural vibration control using dampers can reduce the responses of the structures induced by ground motion effectively.However

the effectiveness depends not only on capacity of damper and related control algorithm

but also on optimal placement of the dampers.Presently

researches on the placement optimization are mainly on the passive control

but are rare on the active and semi-active control devices.In this paper

the authors present an optimal method based on improved genetic algorithm and equivalent quadratic performance index

and it is applied to semi-active control system based on magnetoreological fluid damper.An example study shows that the present method is simple and effective.