SITE-SPECIFIC SEISMIC COEFFICIENT FOR A QUAY WALL ACCORDING TO THE NEW GENERATION OF EUROCODE 8

The evaluation of the seismic performance of geotechnical structures is a significant design challenge due to nonlinear soil-structure interaction, site response effects and ground motion properties. However, the use of advanced analysis methods, such as coupled non-linear dynamic analysis, is not always technically and economically feasible, especially for works of ordinary relevance. For these reasons designers typically rely on the pseudo-static methods and evaluate the seismic action assuming a reference ground acceleration constant in space and time. With such method the system reliability is entirely based on the choice of a conventional ground acceleration to capture all the main factors influencing the seismic action and soil-structure interaction. Codes and recommendations usually define the pseudo-static acceleration considering the stratigraphic effects and the spatial variation with depth of the horizontal ground motion. Following a similar approach, Eurocode 8 (EN 1998-5) draft introduces a new procedure in which the stratigraphic effects and the spatial variation of the ground motion are evaluated from a 1D site-specific ground response analysis. In this paper, this procedure for the definition of the pseudo-static horizontal ground acceleration is applied to a case study of a real quay wall located in the Ravenna port, in Italy. A well-known geotechnical setting and the availability of regional probabilistic seismic hazard studies allowed to perform reliable 1D site-specific ground response analyses by means of the equivalent-linear method. The application of this novel procedure allows for a more realistic representation of the site response without introducing the complexities and the computational costs of advanced dynamic analyses.