No abstract

Estimating of buildings vulnerability is based on a well-organized and detailed database of buildings and their characteristics. Creation of the buildings database of the city Osijek is in progress. This database contains, for each building, information regarding its location, geometric and structural characteristics, materials which were used for structural elements, and other relevant data. This paper presents numerical and statistic values of some characteristics of the buildings from the database. Different methods can be applied for the prediction of damage probability in the field of earthquake risk assessment. With the empirical Macroseismic method and the analytical Capacity Spectrum Method, the vulnerability of the few blocks of buildings, typical for the city Osijek, is estimated. For unreinforced masonry structures with flexible floors, the probability of reaching a certain degree of damage is estimated by the two selected methods, and the obtained results are compared.

The limitation of deformation, the desired level of bearing capacity of the structural elements and the dissipation of the energy produced by an earthquake ensure sufficient bearing capacity, stiffness and ductility of structures. These requirements are met by buildings which are designed and constructed in accordance with the latest technical regulations for buildings exposed to the earthquake. Most of the existing buildings in the city of Osijek do not meet these requirements. It is possible to use a capacity spectrum method for the purpose of considering possible responses of such structures to earthquakes and their estimates of seismic vulnerability. Calculation of seismic vulnerability by this method is based on the expected behavior of the building, obtained by overlapping the demand curve and capacity curve. The performance point is the point at which the capacity curve intersects the reduced response curve, at which capacity and demand are equal. The values of spectral displacement obtained for the performance point of a specific building class are used as the input parameters for the fragility curve for different levels of damage. This method will be applied to the collected database of traditional unreinforced masonry buildings of the city Osijek in Croatia. The database is prepared and the main characteristics of the buildings are processed using geographic information system.

Due to increases in the number of inhabitants and their concentrations in densely populated areas, there is a growing need in modern society to be cautious towards the impact of catastrophic natural events. An earthquake is a particularly major example of this. Knowledge of the seismic vulnerability of buildings in Europe and around the world has deepened and expanded over the last 20 years, as a result of the many devastating earthquakes. In this study, a review of seismic risk assessment methods in Croatia was presented with respect to the hazard, exposure, and vulnerability of buildings in the fourth largest city (Osijek) in Croatia. The proposed algorithm for a detailed risk assessment was applied to a database and is currently in its initial stage.Sustainability 2020, 12, 1796 2 of 24 to estimate the losses. These losses can be assessed in a material form, through the damage of the building stock or non-structural elements of buildings, or in the form of casualties or injuries during the earthquake [10,11]. The last step is to analyze uncertainties, costs, decision-making criteria, etc. The ultimate goal of studying earthquakes and their impact on people and buildings is to create a safer environment, in case an earthquake occurs.The basic elements of the earthquake risk assessment process are shown in Figure 1.Sustainability 2020, 12, 1796 2 of 25 probable intensity in a given geographical area). Then, based on the available data from the exposure model, evaluate the damage using one of the existing vulnerability assessment methods in order to estimate the losses. These losses can be assessed in a material form, through the damage of the building stock or non-structural elements of buildings, or in the form of casualties or injuries during the earthquake [10,11]. The last step is to analyze uncertainties, costs, decision-making criteria, etc. The ultimate goal of studying earthquakes and their impact on people and buildings is to create a safer environment, in case an earthquake occurs. The basic elements of the earthquake risk assessment process are shown in Figure 1.

Assessing earthquake risk and building vulnerability requires an exposure model. These exposure models quantify the building stock in terms of structural characteristics, spatial location, and occupancy. The most significant exposure parameters are the structural characteristics of buildings, which must be uniformly covered by structural typologies. Structural typologies that take into account the regional specificities of design and construction provide more accurate and reliable exposure models. Despite the long history of earthquake engineering in the Republic of Croatia, the assessment of exposure and vulnerability of buildings is a rather new concept, hindered by the fact that no city in the Republic of Croatia has a database on the number, types, and characteristics of existing buildings. The article presents the creation of a building exposure model for the city of Osijek, points out the problems and concerns that the realization process brings, and details the practical solutions and strategies that have been used to achieve the set goals.