Design of Amplified Structural Damping Using Optimal Considerations

A method is suggested to reduce structural response to earthquakes using viscous dampers with their effect magnified by mechanical levers (lever arms). The lever arms are used to magnify the drift and the drift velocities transferred from the structure to the dampers thus producing in larger energy dissipation. An optimal design procedure based on the LQR technique is proposed in this study to obtain the properties of the viscous dampers. The study presents the amplification and the contribution of the construction details to such amplification. A seven-story structure model with the proposed system was simulated in order to check damping efficiency. The increase of energy dissipation in each unit results in a reduction of number of units necessary to achieve the same reduction in structural response to earthquakes, or it results in a reduction of the number of dampers required for same purpose. The use of the proposed technique permits to reduce the number of frame bays obstructed by diagonal or Chevron bracing elements. Introduction Structures designed for seismic regions should be able to absorb and dissipate a large amount of seismic energy in order to maintain the response within acceptable limits. In current practice it is expected that the energy dissipation occur in structural elements through their inelastic behavior, with associated structural damage. Recent efforts were dedicated to finding methods to enhance the building energy absorbing capacity. An extensive research outline can be found in the state-of-the-art publications (Hanson et al., 1993, Soong and Dargush, 1997, Constantinou et al., 1998). Adding fluid viscous dampers in structures is becoming a well-accepted practice and more widely used for eathquake-engineering applications. Constantinou et al. (1992) and Reinhorn et al. (1995) studied analytically and experimentally the influence of supplemental fluid viscous dampers on structural seismic response of elastic and inelastic structures. They concluded that damping is beneficial to reduce deformations and, in elastic structures, reduce also forces and accelerations. Aiken et al. (1996) presented an overview of an extensive dynamic testing program of fluid viscous dampers that was conducted as part of the seismic retrofit of the Golden Gate Bridge. Whittaker and Constantinou (2000) discussed new procedures for the design of buildings incorporating fluid viscous dampers and demonstrated