Layered periodic metafoundation for seismic isolation

In the present thesis the dynamic response of two structures with different foundation, in particular the periodic foundation, are studied. Based on the parametric study of band of frequency gap two kind of periodic foundation are designed. In particular, the layered periodic foundation composed of several concrete and rubber layers, and the periodic foundation composed of concrete layers with interposed rubber blocks, are considered. To test the effectiveness of the isolation ability of these periodic foundations, the dynamic responses of a concrete frame and of a steel frame with the periodic foundations are evaluated and compared with the response of the structures without the metafoundation. First, the analyses are conducted in the frequency domain in order to be able to define the number of unit cell needed to reach the band gaps, previously defined for the infinite periodic foundation. Then, the analyses with sinusoidal waves, in the time domain, show that the waves cannot propagate in the periodic foundation without being attenuated when the frequencies of the seismic wave fall into the band gap of the periodic foundation. Finally, to illustrate the efficiency of these seismic isolation foundations, different ground motion are applied to the structures. The results show that the seismic responses of the structure with the periodic foundation are greatly attenuated as compared with those of the structure without periodic foundation.