Soil-structure interaction effects on the seismic response of a public building in Lefkas, Greece

An investigation of Soil-Structure Interaction (SSI) effects on the seismic response of the Regional Administration building in the island of Lefkas, Greece is performed, based on earthquake recordings from two accelerometric stations installed at the basement of the building and on ground surface at a certain distance from the structure, representing a free-field station. The observed deviation between basement and free-field records is explored by means of a hybrid numerical-analytical formulation in the framework of the substructure approach. To this end, the kinematic part of the interaction mechanism is modeled through commonly employed analytical transfer functions between ground surface and foundation base, while a detailed 3D mass-distributed Finite Element model is analyzed under both fixed and flexible supports to explore the seismic response of the building, as affected by inertial SSI effects. The comparison between predicted and recorded response shows a kinematic dominated response of the foundation that is characterized by strong filtering of the free-field motion at ground surface. Accordingly, various repercussions due to the potential underestimation of the seismic hazard from recording stations housed at the basement of buildings are discussed. Numerical results demonstrate also that soil compliance may have an important effect on the seismic demand quantified in terms of interstorey drifts of the building. Finally, a simplified MDOF lumped-mass stick model of the superstructure is also analyzed under flexible-base conditions, leading to a substantial overprediction of interstorey drifts compared to the 3D model.

Automated summary

The study investigated the effects of Soil-Structure Interaction on the seismic response of a building in Greece, highlighting the deviation between basement and free-field records and discussing potential underestimation of seismic hazard. Numerical results demonstrated the significant impact of soil compliance on seismic demand and the substantial overprediction of interstorey drifts in a simplified model under flexible-base conditions.