Keynote Lecture – On the behaviour of gravity retaining structures under seismic actions
Performance-based design is the goal currently pursued by most of the advanced seismic design codes worldwide. This paper summarises the main findings of recent research carried out at Tor Vergata on the behaviour of gravity retaining walls under seismic actions. Conceptual limitations of direct application of Newmark’s sliding block method to the case of gravity retaining walls are addressed with reference to a simple scheme of two rigid frictional blocks resting on an inclined plane and interacting with one another. The same concepts are extended to the analysis of the active soil wedge-wall system, leading to an extremely simple procedure to compute the relative displacements of a sliding wall when subjected to base accelerations exceeding the critical value. A solution based on the upper bound theorem of limit analysis is then derived for the critical acceleration corresponding to bearing capacity failure, and it is shown that this may be the critical mechanism for realistic mechanical parameters and wall layouts. Experimental evidence from small scale centrifuge tests and results of numerical analyses are used to validate the analytical findings and develop suitable simplified procedures to compute permanent displacements of gravity walls under seismic loading.