Performance of a distributed base isolation system for masonry buildings

The paper presents results from a research study on a new distributed base isolation system for masonry buildings. This system consists of a layer of mortar interposed between the top face of foundations and the shear walls base. The mortar layer is reinforced with vertical mild steel bars, anchored both to masonry walls and to subside concrete of foundations. The proposed system is simple and inexpensive and it is capable of high degree of protection. To demonstrate its effectiveness, the seismic response of a masonry building is investigated by simplified 2 DOFs mathematical model performing numerical analyses in the time domain. Parameters involved in this study were: the fixed-base natural period of the building, the mass ratio, the isolation degree and, the ratio between the yield level of the soft base and the ultimate strength of the shear walls. Comparisons between dynamic responses of fixed-base and isolated models are presented in the form of spectral quantities. Results show that this type of isolation is capable of significantly reducing accelerations at the floor level, with performance comparable to FSI schemes, and an additional advantage of reducing amplitude of residual displacements.