AbstractReducing structural vibrations is one of the main concerns in structural control. Different control techniques are proposed for this purpose. Among the variety of control methods, semi-active ones are very attractive and beneficial in that they require minimum amount of energy but they are very capable to reduce structural displacements. In this paper, the behavior of a structure equipped with a new type of semi-active tuned mass damper called SADA-TMD is compared to the behavior of a structure equipped with active tuned mass damper (ATMD). SADA-TMD is a TMD equipped with semi-active damper actuator (SADA). This device can absorb energy transferred to the ordinary TMD during earthquakes and use it like an actuator; it can also dampen any part of this absorbed energy. For the purpose of comparison a multi story building has been modeled numerically. The performance of SADA-TMD and ATMD is controlled by fuzzy logic controller (FLC). Advantages of employing SADA-TMD to reduce structural responses are shown through illustrations and numerical results. However, the results come from applying SADA-TMD can be compared to that of active tuned mass dampers (ATMD), because SADA-TMD is a semi-active device, the power requirements is significantly lower than those of ATMD. It is worth to be mentioned that because SADA-TMD can work on battery power, it is more reliable than ATMD during strong earthquakes; because the source of energy which is necessary for active actuator could be failed during those earthquakes.