Notes on ground motions defined by Eurocodes

In this paper the seismic input of the last version of Eurocode 8 (EC8) is briefly described and is compared with the previous version. The paper outlines the strong difference between the ground motion in the last version with literature data valid for high seismic zones. Then it highlights some important features related to soil stability. Numerical analyses, with usual methodologies, show that soft soils type D and some of C and E soils are unstable in an Italian first seismic category under the defined seismic actions. This is consequence of the inelastic shear deformation induced by a strong earthquake. Moreover results show that the ground motions given by the EC8 on soft soils are compatible with that on rigid soil, type A, only in low seismic zones. (author)