Centrifuge Modeling of Improved Design for Rocking Foundation Using Short Piles

Rocking foundations have emerged as an attractive design to reduce the seismic loads of structures during strong earthquakes. However, they cannot be applied in the field directly because of the permanent deformation caused by their rocking behavior. To reduce the permanent deformation induced by a rocking foundation, installation of an unconnected pile below the foundation has been suggested as an improved design. The region of significant plastic strains beneath the foundation caused by the rocking behavior is located at a shallow depth; thus, the length of the unconnected pile is reduced relative to the case of connected piles. In this study, to determine the optimized design for a rocking foundation, horizontal slow cyclic tests and dynamic centrifuge shake-table tests were performed for various types of foundation models incorporating short piles. The foundation-structure system was designed to exhibit rocking-dominant behavior. Based on the results of the horizontal slow cyclic tests and dynamic centrifuge tests, the rocking behaviors of the tested models were compared. A setup featuring unconnected short piles with a soil layer is proposed as an optimized rocking foundation design, focusing on the reduction of the permanent deformation of soil.