GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 2.1 GNGTS 2023 Assessment of soil amplification factors of Italian and European building codes using real recordings and numerical simulations A. Famà 1 , G. Andreotti 1,3 , C.G. Lai, 1,2 1 Eucentre Foundation, Pavia, Italy 2 Department of Civil Engineering and Architectural, University of Pavia, Italy 3 IUSS Pavia, Italy ABSTRACT The current Italian building code (NTC18) partially modified the definition of soil classes enforced by the previous version of the technical norm (NTC08) leaving however unchanged the soil factors. More specifically, modifications were introduced with respect to the replacement of the notion of V S30 with that of V S,eq and the increase of the minimum thickness from 20 to 30 meters for soil class E. The latter change had the effect of reducing the overall population of soil classes C and D. Furthermore, the requirement of a thickness greater than 30 meters was removed for soil class B. These changes were not followed by a modification of the soil amplification factors. A numerical study aimed to propose an update of soil factors for the definition of the seismic action (horizontal component) in the Italian building code were carried out in recent years by Andreotti et al . (2018) considering the previous and current version of the Italian building code (NTC08 and NTC18 respectively) and the current version of Eurocode 8 part 1 (CEN 2005). The main objective of this paper is to present an update of the study conducted by Andreotti et al . (2018) using ground motion recordings from real earthquakes from the most accredited international accelerometric datasets. The study aims at (1) defining hazard-dependent soil factors based on the observed ground motion complemented with simulated data (2) quantifying the reliability of current soil factors. INTRODUCTION Most building codes worldwide allow the use of a simplified approach for defining the horizontal seismic action through the definition of 5-6 soil categories to which are associated appropriate soil factors aimed at taking into account one-dimensional litho-stratigraphic ground amplification (in NTC18 and EC8-1 soil category A, V S,eq > 800 m/s and flat surface topography). In NTC18 the soil categories are specified based on the notion of V S,eq which is a generalization of the concept of V S30 . The soil factors modify the shape of the elastic horizontal acceleration response spectra defined for soil category A which is used as reference ground condition (i.e.,