Analysis of pile groups under vertical harmonic vibration

In this paper, a simple method is proposed for the analysis of vertically loaded pile groups under dynamic conditions. The method makes use of the closed-form stiffness matrices derived by Kausel and Roësset [Kausel E, Roësset JM. Stiffness matrices for layered soils. Bull Seismol Soc Am 1981;71(6):1743-61] to simulate the response of layered soils. These matrices are incorporated in a calculation procedure that is essentially analytical. Further computational advantages of the procedure derive from the fact that, under the simplified assumptions of free-field soil displacements and symmetry of the pile-soil interaction forces, the analysis of a pile group may be achieved simply using the solution for the single pile. Moreover, the soil layering effect is reliably accounted for. The accuracy of the method is assessed by comparing the results with those deduced from other existing theoretical solutions. The method is also used to predict the experimental measurements from dynamic tests on pile groups documented in literature.