Dynamic shear stiffness and damping measurements for seismic response analyses at Senigallia, Italy

ABSTRACT. The paper summarises a detailed study on the dynamic characterisation of the Quaternary alluvial deposits of Senigallia, Italy. The research was addressed to the seismic microzonation of the urban area by employing an 1-D linear equivalent model. In the subsoil of the town, Holocene deposits, overlying the marls of the substratum, with depths varying from 15-25m, constitute the most widespread soil of the urban area. The field investigations consisted of down-hole and cross-hole testing in 8 verticals. The dynamic laboratory testing included multistage resonant column tests on undisturbed 15 samples, of which 13 are from alluvial deposits. Comparisons with the experimental data obtained by other Authors for analogous coeval soils revealed a good agreement. With respect to simplified reduction factors for stiffness decay evaluation proposed by Eurocode 8 the alluvial deposits of Senigallia exhibit higher values, thus showing that Eurocode 8 in this case underestimates soil capabilities. Instead, Eurocode 8 overestimate the dissipative properties.