Adaptive base isolation system to achieve structural resiliency under both short- and long-period earthquake ground motions

Base isolation system is widely used to protect important and essential buildings from seismic hazards. The use of high damping is effective in reducing the resonance effect under long-period earthquake ground motions. However, high damping increases the acceleration demand under short-period ground motions, leading to a higher risk of damage of nonstructural components. Actually, low damping is beneficial to reduce the acceleration demand under short-period ground motions, suggesting the use of adaptive damping control, that is, high damping under long-period motions and low damping under short-period motions. In order to implement this concept, a semi-actively controlled base isolation system is provided in this article along with a new control law based on the transmissibility theory. Unlike existing studies, the proposed method enables a systematic design procedure for base isolated structures with semi-active dampers, which is called the simplified design procedure in this article. The performance of the proposed system is evaluated with numerical simulations for a base isolated three-story building with magneto-rheological dampers. It was shown that the proposed system achieves a high level of performance under long-period ground motions, while maintaining the exceptional performance of a conventional base isolation system with low damping under short-period ground motions.