On the performance-based seismic design of yielding retaining structures

This work summarises recent research on the seismic behaviour of displacing or yielding retaining structures, i.e., structures that can undergo permanent displacements during strong earthquakes without failing. For these systems, energy dissipation on shaking, leading to reduced inertia forces, can be achieved by allowing the activation of ductile plastic mechanisms. These must be correctly identified to guarantee the desired strength hierarchy, and depend on the specific retaining structure under examination. It is shown that the critical acceleration, or the smallest value of acceleration corresponding to the activation of the critical plastic mechanism, is the key ingredient for the performance-based design of yielding retaining structures. In fact, the critical acceleration controls both the maximum internal forces in the structural elements and the magnitude and trend of post-seismic permanent displacements and rotations, required for quantitative serviceability and post-earthquake operability assessment of infrastructures. Based on a clear understanding of the physical mechanisms governing the dynamic behaviour of these systems, pseudostatic limit equilibrium solutions and simplified dynamic methods can be developed for their seismic design. Theoretical predictions are validated against data from reduced scale centrifuge models and results of pseudo-static and fully dynamic numerical analyses. Finally, all the results presented in the paper, including experimental, numerical and theoretical findings, are used to provide suggestions for the performance-based design of retaining structures.