Observed Seismic Vulnerability of Italian Buildings

摘要

A very large database of post-earthquake building inspections carried out after the main Italian events of the last 30 years has been processed in order to derive fragility curves for 23 building typologies, mostly referring to masonry structures. The records (more than 91000) of this very complete and homogeneous dataset have been converted into a single damage scale with five levels of damage, plus the case of no damage. For each affected municipality a value of PGA and Housner Intensity (IH) has been evaluated using attenuation laws. Damage probability matrices have been then extracted. These experimental data have been fitted through lognormal fragility curves using an advanced nonlinear regression algorithm also taking into account the relative reliability of each point by the bootstrap technique. The significant concentration of experimental data at low levels of ground motion, associated to the selected analytical expression, determine the peculiar shape of some of the curves, with a very steep initial branch followed by an almost horizontal curve for increasing values of ground motion. Explanations and possible solutions are discussed.