Structural response including seismic soil-pile-structure interaction

The seismic soil - pile - structure interaction (SPSI) can be considered as the combination of two different mechanisms under dynamic loadings. The first one is related to the stiffness contrast between pile and soil (kinematic interaction), whereas the second one is due to the variation of the soil response around the foundation due to the inertial forces generated by the structure (inertial interaction). The evaluation of the contribution of each mechanical and geometrical characteristic of the system in the complex SPSI phenomenon is not trivial. Thus, an effective way to investigate such phenomenon is the analysis of the response of scaled physical model on 1-g an n-g devices. In order to do so, a set of shaking table tests is discussed in this paper. The scaled physical model is formed by a group of piles in a by-layer deposit with and without a single degree of freedom oscillator connected to the foundation with several configurations. This paper assesses the role of the foundation system on the structural response evaluated in terms of period elongation and damping ratio. The input considered is the Tolmezzo earthquake ground motion record from the Friuli 1976 earthquake scaled at the model size. In the paper the experimental results are also compared with classical solutions available from literature.