## 2 Simplified Vulnerability Assessment Methods for Masonry and RC Building Structures
### Historical Seismicity of the Area  
In Italy the classification of the seismic hazard, which is fundamental for the seismic design of buildings, has changed profoundly over the decades. This obviously plays a significant role for seismic risk of existing constructions.  
With reference to the case study, it is worth remembering that the first seismic classification in Italy was introduced in 1927, when a royal decree (R.D. 431/1927 [34]) defined generically two seismic categories. Afterwards, a royal decree in 1935 (R.D. 640/1935 [35]) associated values of expected ground acceleration to those categories: 0.10 g for category I and 0.05 g for category II. In 1975, a more refined seismic hazard map was introduced (D.M. 40/1975 [36]) and extended the hazard to a wider area of the Italian territory than in the past. In 1984, a ministerial decree (D.M. 19.6.1984 [37]) introduced the differentiation of the seismic protection level through a seismic protection coefficient depending on building categories (equal to 1.0 for ordinary structures, 1.4 for strategic constructions, and intermediate values in other cases) in order to define the seismic forces.  
The seismic classification of the national territory was further updated, according to the knowledge and experience of the seismic events recorded during the time. Later, in 2003, a seismic zonation based on the probabilistic values of the expected ground acceleration was introduced (OPCM 3274/2003 [33]). For the first time, the whole national territory was classified as seismic and was divided into four categories. Each category is identified by the value of peak ground acceleration on stiff soil (rock) with an exceeding probability of 10% in 50 years and a corresponding return period of 475 years (i.e., -50 yrs/(ln(1-10%))). For each of the four zones, the seismic design of new buildings was imposed with different levels of severity, with the exception of zone 4, for which the regions were empowered to adopt specific obligation. The new Italian code for buildings in 2008 (NTC 2008 [38]) and its next update (NTC 2018 [39]) definitively abolished the so-called'seismic zonation'. The new code, indeed, introduced a point-by-point mapping of the seismic hazard in terms of peak ground acceleration, defined according to the geographical coordinates of whatever site in Italy and for several return periods.  
In Figure 7, the evolution of the seismic hazard map in Italy from 1935 to 2008 was reported with reference to the above conventional return period of 475 years. The current seismic hazard map for the Campania region reported values of PGA--with 475 years of return period--between 0.07 (southern coast) and 0.26 g (near the Apennines, in the province of Benevento). The schools that belonged to the reference database for this research are located in the province of Naples (therefore medium seismicity), with a PGA value on rock between 0.09 and 0.19 g. It is worth noting that for many areas seismicity was significantly re-evaluated over the time, because the earthquakes occurred in the last decades on the national territory. This means that many buildings designed and built in the past now may have strength incompatible with the current seismicity of the site and a significantly lower safety in comparison with recent constructions.