Empirical fragility assessment of residential buildings using data from the Emilia 2012 sequence of earthquakes

Abstract

In 2012, the Emilia-Romagna region in Italy was affected by ground shaking as well as widespread ground failure (mostly liquefaction) caused by a sequence of earthquakes. The fragility of the residential building inventory is empirically assessed here based on information from 39,087 buildings in 64 municipalities surveyed in order to assess their post-disaster usability. Key (and common) challenge with this type of large post-disaster databases is how best to treat the notable missing data error and address the non-representative sample. Fragility curves for buildings based on their construction material or age are constructed for areas affected by ground shaking and for areas ones affected by ground failure. As expected, old masonry buildings are the most vulnerable and reinforced concrete buildings are seen to be the least vulnerable. Both peak ground acceleration and peak ground velocity have been used to express the intensity measure type. Although, the former was found to fit the data best, it poorly predicted the probability of exceedance of extreme damage to ground failure for building classes associated with small sample sizes (e.g. RC buildings), highlighting the limitations of using non-representative samples in fragility assessment for extreme cases. The fragility curves for masonry buildings compare well with their counterparts based on existing empirical studies