Analyses of a Gravel-Rubber Mixture for Isolating a RC Building

The Geotechnical Seismic Isolation (GSI) is a new solution to mitigate the earthquake effects on superstructures. It consists in improving the mechanical properties of the foundation soil to reduce the seismic energy that reach the foundations. The use of gravel-rubber mixtures (GRMs) is an affordable GSI solution because of their excellent dynamic properties and eco-sustainability. The present paper shows the main results of a numerical investigation on the performance of a GRM layer underneath the foundations of a typical reinforced-concrete Italian building, located in Fleri (Catania, Italy), severely damaged during the 2018 Catania earthquake. The hypothesized GRM layer was characterized by a rubber content equal to 30% per weight. Both the soil-structure system with and without the GRM were modelled. To do so, a 2D FEM approach was used. An equivalent visco-elastic behaviour material for the soil and the GRM was adopted. A visco-inelastic behaviour material for the structure was employed. By comparing the two 2D FEM models (with and without the GRM), it was possible to evaluate the suitability of the GRM as seismic isolation of the structure. Interesting reductions of the spectral ordinates were achieved equal to about 25% and 40% at the foundation level and at the roof of the structure, respectively.