Capacity Design of Retaining Structures and Bridge Abutments with Deep Foundations

Abstract

This paper examines a seismic capacity design approach for retaining structures with piled foundations, which assumes full-strength mobilization in the soil and in the foundation piles during the earthquake. The plastic mechanism activated by the seismic forces consists of a horizontal movement of the structure, involving plastic hinging in the piles. This mechanism is triggered when the seismic inertial forces acting within the structure and the soil mass equal the overall strength of the soil-pile foundation system. The paper describes an iterative procedure for evaluating the critical seismic acceleration that activates the plastic mechanism. The seismic performance of the structure is expressed by its permanent displacements and the corresponding curvature ductility demand in the foundation piles. With reference to an idealized bridge abutment, this procedure is expressed in a fully consistent nondimensional form and is applied to a reference case, to show its potentiality and to discuss the influence of a number of key parameters, such as the soil strength and the foundation geometry on the seismic performance of the structure.