On the design of embedded retaining structures following Eurocodes and the Italian national code.

The paper focuses on the design process of cantilever and anchored embedded retaining structures, following the prescriptions of Eurocodes EC7, EC8 and their implementation in the recent italian Code for Constructions (NTC08). For such structures, the Italian Code prescribes to the designer to perform ULS analyses in static and seismic conditions following the Eurocode Design Approach 1 (DA1). Considering the distinct values of partial factors relevant to the different actions and combinations, the designer generally has to face and to verify the stability of the structure in three distinct cases (i.e.:DA1-C1 and DA1-C2 in static condition; DA1-C2 in seismic condition) in order to assess the most critical one. In the paper, the equations satisfying the fundamental requirement Ed £ Rd for the three cases above are developed in a nondimensional form; this allows to detect the non-dimensional groups (geometrical, mechanical, loading) affecting the rotational equilibrium. Two simple kinds of retaining structure are considered, namely, cantilever and singly-propped embedded walls in cohesionless soil. A parametric study is then performed by considering wide ranges of values for soil friction angle, seismic horizontal coefficient, and unfavourable permanent and variable surcharges. The results obtained from the study, which are summarised into non-dimensional plots, show that often it is not necessary to analyse the three different conditions and immediately provide the most critical case for a wide range of practical situations, in both static and seismic conditions. This leads to a significant usefulness and simplification in current design practice.