Despite significant scientific and technological advancements in earthquake engineering, earthquakes continue to cause widespread destruction of the built environment, often resulting in numerous fatalities and substantial economic losses. Southeastern Europe, which includes Croatia, is part of the Mediterranean–Trans-Asian high-seismic activity zone. This area has recently experienced a series of earthquakes which had severe consequences for both populations and economies. Notably, the types of buildings that suffered significant damage or collapse during these events still constitute a large portion of the building stock across the region. The majority of residential buildings in Croatia and neighboring areas was constructed before the adoption of modern seismic standards, indicating that a considerable part of the building stock remains highly vulnerable to earthquakes. Therefore, the main goal of this study is to identify the building types which significantly contribute to seismic risk, with the focus on Zagreb as Croatia’s largest city and the capital; collect the documentation on the structural systems and occupancy; analyze the data; and carry out the initial vulnerability assessment. This serves as a first step toward developing a new exposure and vulnerability model for Zagreb that is also applicable to all urban areas in the region with similar building stock and seismotectonic conditions.

The city of Zagreb, the national capital and economic hub of Croatia, is situated in a seismically active region and hosts a significant array of historical buildings, from the medieval to Austro-Hungarian periods. These buildings possess varying but generally high degrees of vulnerability to seismic loading. This was highlighted in the Zagreb earthquake of 22 March 2020, emphasizing the need for seismic retrofitting in order to preserve this architectural heritage. In this paper, the seismic capacity of one such unreinforced masonry building is considered through a number of analysis methods, including response spectrum, pushover, and out-of-plane wall failure analyses. Given the advantages and disadvantages of the individual methods, their applicability and value in a seismic analysis is considered. Ambient vibration measurements before and after the Zagreb 2020 earthquake, used for model calibration, are also presented. Conclusions are drawn from each individual analysis and later compared. In conclusion, no single analysis method considers all relevant failure modes, and a combination of nonlinear static or dynamic analysis and out-of-plane analysis is recommended. Due to the large volume of the material, it is published in two parts, with ground motion record selection, dynamic analysis, and a comparison of the results published in part two.

Izgradnja standardiziranih krupno-panelnih zgrada se intenzivirala 1960-ih na području Zagreba. Veliki broj je izgrađen prije prvog ozbiljnijeg seizmičkog propisa (1964). Moderna saznanja pokazuju da su netipični i potencijalno opasni mehanizmi otkazivanja mogući u navedenim krupno-panelnim zgradama. U ovom radu, neke metode za analizu ovakvih građevina su prikazane, uz korištenje programskih paketa ETABS i Abaqus. Detaljni model konstrukcijskih detalja u Abaqusu je korišten za proračun krivulja kapaciteta. Navedene krivulje kapaciteta se onda koriste za kalibraciju jednostavnijeg modela sa plastičnim ponašanjem koncentriranim u čvorovima u ETABS-u. Proces kalibracije je završen usporedbom ponašanja sastavljenih zidova u oba programska paketa radi potvrde točnosti interakcije između krivulja kapaciteta u pojednostavljenom modelu. Rezultat je pojednostavljen numerički model koji može rekreirati relevantne mehanizme loma dovoljno točno.