Large scale soil-foundation-structure model in Greece: dynamic tests vs FEM simulation

This paper provides the results of FEM simulation of dynamic tests recently performed in Thessaloniki on a large-scale single-degree-of-freedom structure resting on a soft soil. The structure (named EuroProteas) was specifically designed to mobilize strong soilstructure interaction (SSI), being a particularly stiff structure founded on soft soil. It consists of a simple steel frame with removable X-bracings founded on a RC slab and supporting the superstructure mass of two RC slabs identical to the foundation slab. It is a totally symmetric structure. Subsoil stratigraphy and dynamic properties of the foundation soil are derived from extended geotechnical and geophysical surveys, including static and dynamic in-situ and laboratory tests. Extensive free- and forced-vibration tests were performed. This paper deals with one set of forced-vibration tests. An eccentric mass shaker was used as a source of harmonic excitation (f input = 3, 4.5, 5, 7 Hz and eccentricity 6.93kg-m) imposed on the roof of the structure. The structural response is recorded by seven accelerometers, five of which are located at the top of the roof slab and two at the top of the foundation slab. Soil response is recorded with seismometers installed on the free soil surface in both horizontal directions. Dynamic FEM modelling of the tests were conducted in the time and frequency domains in order to detect the main aspects of SSI, taking into account soil nonlinearity. Numerical and experimental results were extensively compared. Very interesting results were reached above all in terms of the effects of soil-foundation interface behaviour.