The effect of tie beams on the kinematic response and impedence functions of monopile foundations

The paper focuses on the effect of tie beams on the kinematic response and impedance functions of monopile foundations. Considering a foundation system of a regular framed structure, constituted by monopiles connected with tie beams, a representative portion of the foundation is isolated by suitably modelling its boundary conditions, and kinematic Soil-Structure Interaction analyses are performed exploiting the numerical formulation proposed by Dezi et al. (2009) for the soil-pile system modelling. The model assumes a linear behaviour for the pile and is able to include the soil non linearity in a linear equivalent manner; this allows formulating the problem in the frequency domain where elastodynamic Green’s functions are used to account for the soil-pile interaction and for both the hysteretic and radiation damping. Tie beams are included into the formulation and the problem is solved by means of the finite element approach. A non dimensional parametric investigation is performed by varying the main geometrical and mechanical parameters affecting the whole system response. Results are presented in terms of impedance functions and kinematic response parameters, focusing on the effects of the foundation tie beams on the system response.