A straightforward vulnerability methodology, named FAST approach, for earthquake hazard assessment of infilled reinforced concrete buildings, is carried out using the consolidated probabilistic framework employed in Performance Based Earthquake Engineering.

In the recent decades, earthquake disaster risks in cities have increased mainly due to a high rate of urbanization; thus for areas under possible exposure to earthquakes, it is crucial to implement prevention, emergency and post emergency procedures (Goretti and Di Pasquale, 2006) aimed at a robust quantification of risk and vulnerability of such areas. In the above framework large scale vulnerability approaches become a useful tool aimed at setting intervention priorities in the phases of prevention, emergency and post-emergency.

The FAST approach describes the vulnerability relationships (also called fragility curves) in terms of peak ground acceleration calculated from the estimated mean inelastic drift capacities of infilled RC buildings for various damage states. The damage states are classified according to EMS 98 scale (Grunthal, 1998) and their thresholds are characterized by means of the FAST approach covering the range from slight to heavy damage states (DS1 up to DS3), not including very heavy damage and destruction (the so called DS4 and DS5). DS4 and DS5 are not covered since the vulnerability relationships are carried out on the basis of the typical backbone characteristic of masonry infills, whose influence on damage can be easily quantified up to DS3.

The approach followed is based on the capacity spectrum method and IN2 curves (Dolsek and Fajfar, 2004) that allow switching from damage states characteristic drift to PGA capacity. The probabilistic formulation of the methodology, herein provided, is based on a previous deterministic approach validated on the basis of damage observed after 2011 Lorca (Spain) earthquake, (De Luca et al., 2012).