An innovative approach for reducing the seismic risk of existing buildings and historic sites.

The seismic risk is one of biggest challenges for civil engineers, and a number of mitigation strategies have been developed in time with reference to existing or new buildings. Nowadays, refined techniques based either on structural reinforcement or seismic isolation exist to protect new and existing structures from seismic shaking. This paper presents some results of a research activity in progress at the University of Napoli Federico II (Italy), aimed to check the effectiveness of an innovative approach for reducing the seismic risk by using soft grouting mixtures installed at an optimum depth in the foundation soil. The basic idea is that a thin grouted layer, with a dynamic impedance much smaller than that of the surrounding soil, will filter most of the seismic ground motion, with very little energy being transmitted to the overlying soil. The effectiveness of the insertion of a soft grouted layer in the range of frequency affecting the response of squat buildings was numerically tested via a parametric analyses, with reference to a simplified one-dimensional scheme.