The Role of DSSI on the Seismic Risk Assessment of a Building

The seismic risk assessment is of fundamental importance in a city like Catania (Italy), where there is a medium-high seismic risk. Certainly, the seismic response of structures depends on the Dynamic Soil-Structure Interaction (DSSI), that can be analysed with different levels of details. By preliminary studies at local level, aimed at microzonation studies, or by detailed studies concerning single case histories. The present paper firstly deals with an easy-to-use approach to develop innovative seismic microzonation maps for an urban area of Catania, allowing the evaluation of DSSI effects on a large scale. This methodology is based on the spatial distribution of spectral accelerations, evaluated for the fixed-base structure configuration as well as for the flexible-base one. Then, the paper shows the main results of the numerical modelling of a school building located in the above-mentioned investigated area. The non-linear soil behaviour is modelled by modified shear modulus and soil damping ratio, firstly evaluated according to EC8 suggestions (2003) and secondly considering the reached effective strain level by the G(γ) and D(γ) curves. The response of these FEM models is analysed by investigating the soil filtering effect and estimating how the different modelling of the soil non-linearity can impact on the behaviour of the full-coupled system.