A simplified approach to dynamic analysis of pile groups in sand

Pile foundations supporting bridge piers, offshore platforms and marine structures are required to resist not only static loading but also lateral dynamic loading. The static p-y curves are widely used to relate pile deflections to the nonlinear soil reactions. The p-multipliers are used to account for the group effect by relating the load transfer curves of a pile in a group to the load transfer curves of a single pile. Some studies have examined the validity of p-multipliers concept for the static and cyclic loading cases. However, the concept of p-multipliers has not been considered yet for the dynamic loading case. This is attempted in the current study. An analysis for the dynamic lateral response of pile groups is described. The proposed analysis incorporates the static p-y curve approach and the plane strain assumptions to represent the soil reactions within the frame of a Winkler model. The model accounts for the nonlinear behavior of the soil, energy dissipation through the soil and the pile group effect. A parametric study was performed employing the proposed analysis and the results were used to establish dynamic soil reactions for single piles and pile groups for different types of sand and harmonic loading with varying frequencies applied at the pile head. Dynamic p-multipliers were established to relate the dynamic load transfer curves of a pile in a group to the dynamic load transfer curve for a single pile. The dynamic p-multipliers were found to vary with the spacing between piles, oil type, peak amplitude of loading and the angle between the line between any two piles and the direction of loading.