J. Alamatian - Assistant Professor, Civil Engineering Department, mashhad branch,islamic azad university mashhad iran
B. Karimpoor - phd candidate, civi; engineering department inustrial university of shahroud
M.H Shahani - Msc student Civil engineering department, mashhad branch islamic azad university mashhad, iran

this paper deals ith new approach for controlling the structral vibrations. The proposed active control method is based on structural dynamics theories in witch several actruators and sensors are used. Each actuator force is modeled as an equivalent viscous damper so that several loer vibration modes are damped critically. this subject is schieved by simple mathematical formulation. the presented method does not depend on the type of dynamic load and it could be applied to control structures with multi degrees of freedom. for numerical verification of proposed method. the time history of controlled displacememnt is evaluation in five story shear building , subjected to the elcentro base excitation . this study shows that the proposed method has suitable efficiency for reducing structural vibration.

active Control ,critical damimg, Structural dynamic theories