Seismic vulnerability assessment of an old historical masonry building in Osijek, Croatia, using Damage Index

Osijek is the largest city in eastern Croatia and the fourth largest city in the country. The most preserved Baroque buildings of Croatia are located in Tvrdja, the old historical city core. Tvrdja represents the educational, cultural and administrative centre of Osijek, and consists of 106 buildings. One of the problems facing civil engineers today is preserving a large number of older masonry buildings, built in areas of seismic active zones. It is very important to evaluate the existing earthquake resistance of these buildings in order to strengthen existing buildings and/or prepare emergency plans using realistic seismic scenarios. Therefore, it is desirable to provide a relatively fast but accurate seismic vulnerability assessment, which the proposed method in this paper satisfies. The aim of the article is to determine, using Damage Index coefficient, the seismic vulnerability of a historical building located in Tvrdja. For the analysed area, a set of seven earthquake records is specified, and using different structures modelled as single-degree-of-freedom systems, Damage index spectral functions are determined. Thus, by knowing the proposed parameters of a single-degree-of-freedom system representing an unreinforced masonry building, a response of the structure to a given earthquake can be determined using the graph of Damage index spectral functions.