Torsional dynamic response of rigid footings and pile foundations for various end-conditions

An analysis for torsional dynamic response of rigid footings and pile foundations with various end-conditions: half-space, soil stratum, and end-bearing is demonstrated. The interaction adjacent to footing/pile is simulated through the Vlasov-Leont′ev foundation model. Because of stress singularity at the pile/footing base, the end-conditions (half-space and soil stratum) at the foundation base are incorporated in the boundary conditions of the analysis through expressions in literature. The expressions are obtained from the torsional dynamic response of a rigid disk welded to the surface of the viscoelastic media. Several expressions, from various formulations, are employed, and the degree of accuracy of each expression is assessed through an extensive comparative study with rigorous and simplified solutions in the literature. The expression that is most accurate and captures the mechanics of the interaction problem in a half-space/soil stratum is extracted and proposed. The accuracy of the Vlasov-Leont′ev foundation model is also assessed for end-bearing pile foundations. For each end-condition, parametric studies are also performed for a wide range of frequencies, and pile-slenderness and stiffness ratios, and appropriate conclusions derived from the studies are reported. Comparisons with experimental results are shown to demonstrate the applicability of the analysis to geotechnical engineering practice.