Narrow Results

An analytical solution is presented for evaluating the dynamic responses of pile groups subjected to vertical harmonic loads. The solution allows us to consider the effects of pile geometry on the pile head impedance of the vertically loaded pile groups by the use of a new dynamic interaction factor. To this end, the stress distributions of the soil surrounding the vertically vibrating pile is first determined for calculating the pile–pile interaction factor, instead of the classical interaction factor based on two-pile displacements in past studies. Accordingly, the impedances of the pile group are derived using the proposed pile–pile interaction factor and the superposition principle. Some selected examples are presented to demonstrate the proposed refined technique for evaluating the dynamic characteristics of the pile group.

A simplified expression is derived for the dynamic stiffness of grouped piles subjected to lateral loading. A computer program, based on the Thin Layered Element Method, is used for this purpose. The results of the program are compared with rigorous solutions. The simplified expression of the dynamic stiffness of grouped piles, where the mass, damping and stiffness parameters are frequency invariant, will be particularly useful for an equivalent linear analysis of the interaction between nonlinear soil and grouped piles in real time.