Relevance of soil-pile tangential tractions for the estimation of kinematic seismic forces: Formulation and setting of a Winkler approach

The effects of considering the tangential tractions that act on the soil-pile interface in the estimation of the pile seismic response are studied through a Beam on Dynamic Winkler Foundation model, which includes the distributed moments produced by the rotation of the pile cross-section and the action of the incident field. The performance of the developed Winkler formulation is evaluated by using a rigorous continuum model based on boundary elements that allows the use of both smooth and welded contact conditions at the soil-pile interface. In order to do the analyses, the seismic response of a fixed-head single pile embedded in different soils subjected to planar shear waves is computed in terms of envelopes of maximum bending moments and shear forces. Two soil profiles are assumed: homogeneous and two-strata halfspaces. The tangential tractions are found to significantly increase the pile maximum shear forces, but to have a minor impact on the pile maximum bending moments. The proposed Winkler model accurately reproduces the results of the continuum formulation for both contact conditions. However, some differences are found in the evaluation of the inter-layer envelopes, for which the simplified model underestimates their values.