he study investigates on the inelastic response of equivalent Simple Degree Of Freedom systems (SDOF) to some L’Aquila earthquake accelerograms recorded in the epicentral area. According to recent statistical analysis, L’Aquila earthquake is considered as a seismic event having a return period of about 475 years. The aim of the paper is to give a first interpretation to the high damage levels (IX-X MCS) due to the earthquake, in spite of its moderate magnitudo (ML = 5.8) and the correct historical seismic classification of the stroked area. The study thus analyzes the inelastic seismic demand of a SDOF, designed according to the NTC08, to four near-fault accelerograms recorded during the L’Aquila earthquake main shock, by varying SDOF capacity in terms of strength, ductility and viscous damping, in order to assess the performance targets imposed by the same NTC08. Two well- known damage indices have been used to estimate seismic effects on built environment: Park & Ang and low-cycle fatigue indices. The results highlight the high seismic inelastic demand, well beyond the limit specified in NTC08, both for the design of new buildings and for seismic upgrading of existing ones. This clearly shows the need for a revision of the actual seismic hazard map taking into account the near-fault and site amplification effects, which are not considered within the seismic hazard methods adopted by the NTC08.
For this paper is available an extended abstract after the text in Italian