# Seismic Vulnerability Assessment of Historical Masonry Buildings in Croatian Coastal Area
## 2 Seismic Vulnerability Assessment of the Test Site
### Vulnerability Index Results  
The vulnerability indexes for 75 buildings in the historical core were calculated and all collected data were digitalized. Some of these buildings are located in several cadastral parcels and have different owners, but they were put in the same class because of their structural integrity. To improve the interpretation of the results, these individual vulnerability parameters, as well as other important input information, were integrated into a geographical information system (GIS) tool. The GIS software adopted in this study was the open-source suite ESRI ArcGIS Runtime 100.4 v1, in which geo-referenced graph  
Figure 6: (**a**) Location of the Kastela City on the Dalmatian coast. (**b**) Position of the seismic lines in the historic center of Kastela [47]. ical data (vectorized information and orthophoto maps) were combined with building parameter information. The buildings were divided into 4 vulnerability classes: low vulnerability for \(\mathrm{I_{v}}<30\), medium-low vulnerability for \(30<\mathrm{I_{v}}<45\), medium-high vulnerability for \(45<\mathrm{I_{v}}<60\), and high vulnerability for \(\mathrm{I_{v}}>60\). Figure 7 shows the vulnerability map of the area, whereas the distribution of the vulnerability is shown in Figure 8. Most buildings in the historical core belonged to the high vulnerability class (25%) and to the medium-high vulnerability class (47%). A small number of buildings were classified as medium-low vulnerability (21%). Only a few buildings were of low vulnerability (7%), and these were old stone buildings that were reconstructed. Buildings with vulnerability index of 45 and larger were considered highly vulnerable, as expected, given the age of the town center. The indexes ranged from 11.1, corresponding to one of the newer houses that was completely renovated at the boundary of the core, to 76.9, the vulnerability index of the Cambi tower. Houses made of poorly connected walls, with flexible floor structures, irregular in layout and height, were revealed to be more endangered. In addition to these basic aspects, the degree of general preservation of the building and the presence of subsequent reconstructions significantly affected the vulnerability indexes. The investigation of the parameters necessary for evaluating the seismic vulnerability index allows us to characterize and draw some indicators that can help to better understand the overall vulnerability results. The spatial distribution of these parameters was analyzed and the results are shown in Figure 9.  
Figure 8: Vulnerability index distribution in the historical core. Figure 7: Vulnerability map of the historical core. Figure 9: Cont. We first focused on parameter \"type and organization of the resistant system\", which measures the presence of connections among perpendicular walls and connections among floors or roofs in masonry buildings, which are necessary to ensure the three-dimensional box behavior of the building. We detected that about 77% of the buildings were made without any confining elements and with poorly connected stone walls (class D), whereas 21% were also made without confining elements but had strongly connected walls (class C). Only 1% were in class A, having been reconstructed. Most buildings were made without confining elements (classes C and D), this being one of the main aspects that can lead to significant damage and to the separation of the walls. The \"quality of the resistant system\" parameter is based on the type of masonry, considering the type of material, the shape of the elements, and the homogeneity of the walls. Figure 9b shows the distribution of the buildings between vulnerability classes A to D, with 3%, 3%, 57%, and 37% of buildings, respectively. The majority of them belonged to classes C and D, indicating medium to high vulnerability. The \"conventional resistance\" parameter estimates the maximum shear strength of the structure, accounting for the resistant area of the walls in the two main horizontal directions.