On the seismic design of displacing earth retaining systems

Although the actual seismic behaviour of earth retaining structures is a complex soil-structure interaction phenomenon, in the engineering practice these systems are designed with unsophisticated tools. It is then essential to develop design methods that on the one hand are based on the recent concepts of seismic performance and capacity design, and on the other hand are simple enough to be readily implementable in real projects. This paper contributes to the development of a new design strategy: it shows that the gradual mobilisation of the resistance of the system, from the initial static condition to the development of a plastic mechanism, can be expressed through a well-defined capacity curve, and that this curve can be used to predict the seismic performance of the system, in terms of residual displacements and maximum internal forces in the structural members. This has important implications, because the essential ingredients of the capacity curve can be derived with a simple analysis of the plastic mechanism, making the proposed approach either directly applicable in a displacement-based design method, or functional to the development of equivalent force-based design approaches.