A practical procedure for time-domain soil-structure interaction analysis of structures on pile foundations

The paper presents a simplified procedure for the time domain soil-structure interaction analysis of piled structures, based on the use of a lumped parameter model for the approximation of the frequency-dependent dynamic stiffness of foundations. The lumped model can be implemented in commercial software to perform linear or nonlinear dynamic analyses of structures founded on piles taking into account the frequency dependent coupled roto-translational, vertical and torsional behaviour of the soil-foundation system. Closed-form formulas, calibrated with a nonlinear least square procedure based on data provided by an extensive nondimensional parametric analysis, are used for estimating parameters of the lumped system. Formulas, which allow defining lumped models representative of pile groups with square layout and different number of piles embedded in soft and stiff soils, can be straightforwardly implemented to perform inertial structural analyses accounting for the dynamic behaviour of the soil-foundation system. Some applications on typical bridge piers are presented to show a practical use of the proposed procedure. Results demonstrate the capability of the approach in capturing the actual dynamic response evaluated through a rigorous soil-structure interaction analysis.