Keywords: rubber-soil mixture, distributed base isolation, soil-structure interaction.

This paper investigates, through numerical simulations and parametric analyses, the possibility of using a rubber-soil mixture as the foundation soil for a building [1,2,3,4,5] in order to favourably affect its response under earthquake excitations. The aim of this research work is to assess the beneficial effects of using such a granulated rubber-soil mixture under the foundation of a five-storey building, as a kind of distributed seismic isolation with a low cost. The structural system, including the soil and the rubber-soil mixture, is simulated using the finite element method by means of the commercially available software SAP2000. The computed peak top-floor accelerations of the building under various earthquakes without and with the replacement of the foundation soil with a rubber-soil mixture are compared. The results from the numerical simulations and parametric studies indicate that the properties of the intervention layer influence considerably the analysis results. In general, the peak absolute top-floor accelerations tend to decrease with the reduction of the elastic modulus and the increase of the damping ratio of the rubber-soil mixture, but they are mostly influenced by the content of the excitation frequency. Nevertheless, the decrease of the peak response of the building is not as significant as when actual seismic isolation is employed. In the latter case, the cost is much higher than that of using the rubber-soil mixture in the foundation of a building, where a seismic gap is not required around the building.

1

M. Yegian, U. Kadakal, "Foundation isolation for seismic protection using a smooth synthetic liner", Journal of Geotechnical and Geoenvironmental Engineering, ASCE 130(11), 1121-1130, 2004. doi:10.1061/(ASCE)1090-0241(2004)130:11(1121)

2

H.H. Tsang, "Seismic isolation by rubber-soil mixtures for developing countries", Journal of Earthquake Engineering and Structural Dynamics, 37, 283-303, 2008. doi:10.1002/eqe.756

3

K. Senetakis, A. Anastasiadis, K. Trevlopoulos, K. Pitilakis, "Dynamic response of SDOF systems on soil replaced with sand/rubber mixture", Proceeding of the ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering, CD370, Rhodes, Greece, 2009.

4

E. Kirtas, E. Rovithis, K. Pitilakis, "Subsoil Interventions Effect on Structural Seismic Response. Part I: Validation of Numerical Simulations", Journal of Earthquake Engineering, 13, 155-169, 2009. doi:10.1080/13632460802347463

5

E. Kirtas, K. Pitilakis, "Subsoil interventions effect on structural seismic response. Part II: parametric investigation", Journal of Earthquake Engineering, 13, 328-344, 2009. doi:10.1080/13632460802347471

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