Amirhossein MIRKOOSHESH - MS., University of Science and Culture,Tehran,Iran
Ali NIKKHOO - AssistantPro fessor,University of Science and Culture, Tehran, Iran

In this study, in order to reduce undesirable vibrations which is caused by seismic loads in structure a special type oftuned mass damper( TMD) named doubletuned mass damper (DTM D) has been surveyed to find optimal characteristics of thisdamper and it’s efficiency in comparosion withtuned mass damper.Doubletuned mass damperc onsists of one large and one smaller tuned ma ss damper for achieving more effective and more capable system to reduce undesirable vibrations resultiing from seismic loads. Therefore the damper was located in roof storey of 5 and 10-storey structures withh steel frames and about 850time history analyses have been done by considering nonlinear behavior of the structure. The criteria of this study is displacement of stor eys and the trial and error method has been used for obtaining the specifications of damper.The result shows that double tuned mass damper is more effective than tuned mass damper in order to reduce the displa cement responses of these structures and in addittionsome tables has been presented for extracting the optimal characteristics of two types of dampers.

Tuned Mass Damper (TMD), Double Tuned Mass Damper (DTMD ), Nonlinear Behavior, Passive Control