Site response analysis for the seismic improvement of a historical and monumental building: the case study of Augusta Hangar

Eastern Sicily is very rich of historical buildings, but at the same time is one of the most seismically active areas of Italy. In particular, the city of Augusta was damaged by the January 11, 1693 Val di Noto Earthquake, as well as some others Sicilian cities. Afterwards, the strongest earthquake, about 300 years later, was the Sicilian Earthquake of December 13, 1990, with an epicenter close to Augusta and maximum intensity of VII–VIII MCS. In order to study the geotechnical dynamic characteristics of the foundation soil of the Augusta Hangar, in situ investigations and laboratory tests have been carried out. Among in situ investigations, borings, standard penetration tests (SPT), field vane tests (FVT), Ménard pressure meter tests (MPT), down-hole tests (DHT) have been carried out. Among laboratory tests oedometer tests, direct shear tests (DST), consolidated drained triaxial tests (CDTXT), n. 6 undrained triaxial tests (UTXT), cyclic loading torsional shear tests (CLTST), resonant column tests (RCT) have been carried out. Special attention has been devoted to the variation of the Young modulus non-linearity, shear modulus G, and damping ratio D by cyclic loading triaxial tests and resonant column tests. This paper tries to summarize this information in a comprehensive way in order to provide a representative geotechnical model of the site where an important historical building is located. Processing of all these data also allowed the ground response analysis at the surface, in terms of time history and response spectra, using as input in the linear-equivalent codes EERA, STRATA, and DEEPSOIL both synthetic seismograms and recorded accelerograms. The results of the ground response analyses represent useful tools for the safeguard of historical buildings and have been used for the planning of the seismic improvement interventions.