The dynamic modeling of the half-plane by finite elements

A comparison was made between the vertical, rocking and horizontal impedance functions for a rigid strip foundation placed on homogeneous soil obtained by the finite element approach and the corresponding functions obtained for an elastic half-plane. An attempt was made to determine the overall size of the finite element model and the material damping necessary to approximate the two-dimensional half-plane results over the frequency range of interest. The results of this study indicate that even for large overall sizes of the model, the impedances obtained by the finite element approach present important oscillations depending on the value of the frequency. Such oscillations may be reduced by further increasing the overall size of the model or by increasing the material damping; however, the last approach would lead to an overestimation of the radiation damping. The errors associated with the vertical, rocking and horizontal impedances are of different magnitudes, the largest corresponding to the vertical impedances. The size of the elements was chosen such that the impact on the results obtained was minimal. It is expected that the use of larger size elements would further complicate the modeling problem.