Sensitivity analysis of seismic soil-foundation-structure interaction in masonry buildings founded on cavities

Historical urban centers are often characterized by cavity systems beneath the foundations or underground stories of masonry buildings. This may have an impact on the expected damage induced by earthquake excitations. This paper presents the nonlinear dynamic analysis of a historical multistory building made of stonemasonry load-bearing walls and horizontal diaphragms, taking into account the complex interaction between the foundation system and soil. The aim of this research is to evaluate whether and how the presence of an underground floor and cavity influences the Soil-Foundation-Structure (SFS) interaction. Dynamic analyses of 2D SFS models were performed with the finite difference method (FDM), by varying geotechnical and structural properties such as the soil stratigraphy, the basement depth and the number of building stories. The main results of 234 dynamic linear elastic analyses are presented in a dimensionless format. A new equivalent wave parameter was properly defined to take into account the presence of underground level and cavities in SFS interaction. Relationships between the most important parameters controlling the interaction phenomena are proposed. Since the geometric layouts considered in this study are rather recurrent in the Italian and European built heritage, the proposed procedure might be widely extended to comparable cases.