The cost-effectiveness of active control of structural systems for protection against seismic hazards is examined. Considerations include uncertainties in the earthquake occurrence and intensity, damage reduction vs control actuator capacity, linear vs nonlinear structural behavior, structural exposure time, discount of cost of future structural failure in present dollar value, and cost of maintenance of control devices. Parametric studies of the expected life cycle cost of structures under seismic loads with and without the control device are carried out and compared for linear systems. The effectiveness of the control is also investigated when the excitation level is high and the structure becomes inelastic. The results show that the effectiveness drops significantly. Expensive, large capacity control devices are generally not cost-justifiable.
