A synthetic formulation for the Italian seismic hazard and code implications for the seismic risk

• Published in: Soil dynamics and earthquake engineering (1984) 2015-10, Vol.77, p.111-122
• Main Authors: Vanzi, I., Marano, G.C., Monti, G., Nuti, C.
• Format: Article
• Language: English
• Subjects: Bedrock; Code calibration; Computation; Hazards; Limit states; Mathematical models; Nonlinearity; Reliability; Seismic hazard; Seismic phenomena; Seismic risk; Structural safety; Surface spectra
• ISSN: 0267-7261; 1879-341X
• DOI: 10.1016/j.soildyn.2015.05.001

The paper contains two parts. In the first one, the seismic hazard on the Italian territory, as given by the current Italian structural design code, published in 2008, is discussed. Hazard curves, given by the Italian code in a tabular form, are fitted with a single non-linear model and it is shown that a more compact, simple and user-ready territorial hazard description can be applied. The model is valid for both the bedrock and the surface seismic hazards, and is accurate. The surface seismic hazard is computed with a local amplification mapping, which is now well detailed over the entire territory. Departing from these results, in the second part the territorial seismic risk for the ultimate limit state is computed via a parametric fragility curve. From the results, it can be inferred that the codes need further factors calibration, with the aims of guaranteeing both territorially uniform reliability levels, and the traditionally assumed target reliability levels, e.g. those stated in the Eurocodes. •We model the Italian seismic bedrock hazard with a linear (in double log scale) law.•We extend the hazard model to account for local soil amplification.•We model risk and compute structural resistance compliant with Eurocode safety.•Implied required ductility is high and equal to about 3.5q (equal displacements).•The PGA of the design action for ultimate limit state should be proportional to the 2475 years ground motion.