Semi-active control strategies for buildings subject to near-field earthquakes

The near-field earthquake ground motion is characterized by high peak accelerations and velocity pulses with long period components as well as large ground displacements. Such characteristics are responsible for severe damages to flexible structures. The peak ground acceleration occurs in the form of a shock, rather than a gradual build-up. As a result, passive dampers may not dissipate energies quick enough to prevent a serious damage to structures. Recently, a resetting or switching semi-active stiffness damper (RSASD or SSASD) and a semi-active electromagnetic friction damper (SAEMFD) have been shown to be effective in reducing the structural response due to dynamic loads. In this paper, the performance and effectiveness of these two semi-active hybrid isolation systems are studied extensively for base-isolated buildings subject to near-field earthquakes. Numerical results clearly demonstrate that these two semi-active dampers are effective in protecting the integrity of base-isolated structures during near-field earthquakes.