Dynamic Modeling and Response of Rigid Embedded Cylinders

Following a brief review of the limitations of a popular technique for modeling the soil action in analyses of the dynamic response of deeply embedded cylindrical foundations and structures, the sources of the limitations are identified and a modification is proposed that, while retaining the attractiveness of the original model, defines correctly the action of the system. In the proposed approach, the soil medium is modeled by a series of elastically constrained, rather than unconstrained, thin horizontal layers with a circular hole at the center. The impedances of the constrained layers are established and are then used to evaluate the dynamic response of a rigid vertical cylinder embedded in a uniform viscoelastic stratum of constant thickness and infinite extent in the horizontal direction. The cylinder and the stratum are presumed to be supported on a nondeformable base undergoing a uniform horizontal motion. The effects of both harmonic and earthquake-induced ground motions are considered. The response quantities examined include the dynamic force per unit of cylinder height and the corresponding base shear and base moment.