Equivalent linear model for the lateral dynamic analysis of pile foundations considering pile-soil interface degradation

An equivalent linear BEM-FEM model for the approximate analysis of the time harmonic lateral response of piles considering soil degradation along the soil-pile interface is proposed. The non-degraded soil around the foundation is modelled with boundary elements as a continuum, semi-infinite, isotropic, homogeneous or zoned homogeneous, linear, viscoelastic medium. Piles are modelled with finite elements as beams according to the Bernoulli hypothesis. Differently from what is considered in other BEM-FEM coupled numerical schemes, welded contact conditions are not assumed herein between piles and soil. On the contrary, displacements along FEM piles and within BEM soil are related through distributed springs and dashpots whose properties vary along the pile and that represent the varying stiffness and energy dissipation properties of a pile-soil interface with different levels of degradation at different depths. The developed numerical model is verified by comparison against a more rigorous but much more costly multi-domain boundary element model in which the same degraded soil regions around the pile are modelled as three-dimensional regions.