Due to the size, power, energy dissipation, and performance constraints associated with passive structural control methods, active control methods, employing hydraulic, or other force-generating devices, have received attention. Active devices, with external power sources (such as hydraulic pumps), can be compact for the amount of force that can be generated within these devices. Therefore, performance goals can be achieved with few active control devices that would require many passive devices. As with many control systems, performance goals are secondary to stability. The stability of actively controlled systems with uncertain or time varying properties can be a major concern. Semi-active control devices (in which passive device properties can be modulated) implicitly address the stability issue and allow a degree of adaptability to the structural control. Since these control methods often have non-linear characteristics, and because peak responses are of primary concern for earthquake hazard mitigation, the performance of actively, or semi-actively controlled systems is evaluated using time-history analyses. The proposed benchmark control problem for seismically excited buildings enables various control methods to be systematically compared.
This paper presents the performance of an optimally damped structure, using passive viscous dampers. The force-velocity properties of the damper will be modeled with a power-law relationship. The sizing and placement of the dampers will be designed according to H2 synthesis techniques and linearized models for the dampers. It is anticipated that the behavior of the passively controlled systems will illustrate the competing requirements of absolute acceleration attenuation with deformation attenuation.