Effectiveness analysis of a semiactive base isolation strategy using information from an early-warning network

• Data from a Seismic Early Warning network to the site to be protected are processed.
• A new algorithm using the FFT is adopted to estimate the structural seismic demand.
• Semiactive devices are driven to modify base isolation layer mechanical proprieties.
• Strategy is effective even when structural system is located close to the epicenter.
• Results suggests for practical application, namely ad hoc EW system for critical facilities.

In this paper the possibility to manage data transferred by a Seismic Early Warning network to protect from collapse Base Isolated strategic structural systems by using semiactive devices has been investigated. In particular, by estimating the frequency content of the incoming seismic signal recorded at the accelerometric stations using a Fast Fourier Transform (FFT) technique, a new approach is proposed to estimate the seismic demand of the structure to be protected in order to eventually modify its mechanical features by means of semiactive devices. The analysis concerns a Base Isolated benchmark system equipped with semiactive devices located at the isolation layer, capable of modifying both the stiffness and damping of the overall structural system.The effectiveness of the proposed strategy has been tested on varying the “anticipation time”, namely the range of the time interval between the start of the seismic data elaboration by the recorded stations and the arrival of the seismic S-wave to the interested site, the added stiffness and damping resources, as well as by taking into account different seismic input signals.The results highlight the practical feasibility of the proposed strategy as well as the critical role played by the considered parameters on the performance of both the isolation level and superstructure. This work has to be intended as a first contribution concerning the potentiality of the Early Warning applications in reducing the seismic risk in built environments.