Deriving soil-foundation-pier physical parameters from dynamic identification tests on bridges

The paper presents a methodology for the identification of the physical parameters of a model describing the transverse dynamics of soil-foundation-pier systems founded on piles, starting from results of dynamic experimental tests. In detail, the procedure exploits the identified state-space model of the system obtained from results of dynamic tests through consolidated identification techniques available in the literature. The procedure permits the physical parameters of the real system (e.g. masses, pier stiffness matrix, and soil-foundation impedance) to be computed by directly comparing the components of the analytical and identified stiffness, mass and damping matrices; the latter extracted from the identified state-space models. The proposed approach allows the direct definition of the numerical model that best fits the experimental data, and permits the identification of the soil-foundation compliance. Firstly, the dynamics of the analytical model, which includes the frequency-dependent behaviour of the soil-foundation system through the introduction of a lumped parameter model, is formulated adopting the continuous-time first-order state-space form. Then, an identification strategy of the physical parameters of a soil-foundation-pier system is proposed, starting from the discrete-time state-space model identified from dynamic tests. Finally, a numerical illustration is proposed to show the approach potentials.