Pile groups are often over-designed due to the conservatism of the current design methods. A small under-estimation of the vertical bearing capacity of the single pile can lead to a substantial under-estimation of the moment capacity of the entire pile group. A reliable estimation of the moment capacity is crucial and can reduce costs, since seismic loading is typically critical for retrofit design.
Existing methods for the estimation of the bearing capacity will be refined for more accurate results. Available data (CPT, pile-load tests) will be used in conjunction with centrifuge tests and numerical analyses. An innovative method for the measurement of the actual pile-group stiffness using an eccentric vibrating mass will be developed and tested in the centrifuge. The possibility of deriving correlations between stiffness and strength will be derived.
Subsequently, the potential of introducing the concept of ductility in pile design will be explored. An increased pile-group moment capacity can be obtained by allowing the edge piles to reach their full bearing capacity and by progressively mobilizing the capacity of the inner piles. In this way, a ductile energy dissipation mechanism develops at the pile-soil interface at the cost of residual deformations that can be accounted for in design.
