This paper shows how Tuned Mass Dampers can provide seismic protection for structures. These dampers consist of a relatively small mass, a spring, and a dashpot attached to a point of maximum vibration and in resonance with the structure to which they are attached. They are widely used to control the response of buildings, bridges, towers, chimneys and other structures to wind forces, machine vibrations and occupant activity. For the most part however, these dampers have been considered ineffective to reduce the seismic response of structures. This paper demonstrates that such devices can be used effectively to control the seismic response of structures. The paper presents a basic mechanism that explains under what conditions such dampers may work effectively under earthquake loads. It also provides recommendations for the selection of the mass, stiffness and damping factors. It includes the results of a series of numerical and experimental tests which verify that properly designed Tuned Mass Dampers effectively and consistently reduce the response of many types of structural systems to various types of earthquake excitations.
