Seismic performance and design approach for friction dissipative foundations

The seismic actions transmitted to a structure can be limited by inserting a frictional system between the foundation and the underlying soil. This allows a controlled sliding when the seismic forces reach a given critical value, that should be chosen to provide a desired seismic performance of the structure. Although this type of dissipative foundation has recently been adopted for the towers of two long-span bridges (the Rion Antirion and the Izmit Bay bridges), its design still requires the development of a clear and robust design approach. In this view, the present paper studies the response of dissipative foundations, developing a generalised non-dimensional formulation that can be useful for design. Specifically, the dynamic response of the foundation is analysed using a Newmark rigid block model, that is modified to account for the multi-directionality of the ground motion and to include a simplified description of the dynamic response of the superstructure. The model is firstly validated against the results of three-dimensional non-linear dynamic analyses of a specific case study. Subsequently, the main factors affecting the dynamic response of the dissipative system are highlighted through an extensive parametric study. The results of this study are finally used to develop a design approach aimed to maximise the efficiency of the dissipative device, relating the optimum mechanical properties of the dissipative contact to the dynamic characteristics of the entire soil-structure system.