Evaluation of models for laterally loaded piles

It is common in the analysis of piles under lateral loads to use a model of a beam on elastic foundation, or a finite element model with the pile represented by a one dimensional beam-column with its axis coinciding with the central line of the finite element mesh. In both cases the lateral stiffness of the pile itself, as a structural element, is a function of the product of its Young's modulus of elasticity by the moment of inertia of the cross section (EI). For solid piles the moment of inertia is directly related to the radius but this is not the case when dealing with hollow piles where the value of the radius corresponding to a given moment of inertia is not unique. Both of the above models ignore the effect of the value of the radius of the soil cavity occupied by the pile. In this work a more accurate model of the pile with the soil around it represented. A consistent boundary matrix valid for static and dynamic analyses is used to evaluate the accuracy of the results provided by the model of a beam on elastic foundation. In addition, a 1D model of the pile is analyzed with finite elements for the soil. This analysis considers a fixed value of the product EI, but a variable radius in order to illustrate the importance of the radial dimension. Results are obtained for a pile fixed at the bottom, but long enough so that the top boundary conditions do not affect the results and for a shorter floating pile were the shear and moment at the bottom resulting from the underlying soil would not be zero. For the beam on elastic foundation model, the top of the pile was assumed to be fixed.