Seismic vulnerability of historic masonry buildings in Vienna (Austria): influence of structural and material parameters

Abstract

Historic unreinforced masonry (URM) buildings from the “Gründerzeit” period (≈ 1840–1918) of the Austro-Hungarian Monarchy represent a substantial part of Vienna’s building stock and are particularly vulnerable to seismic action. While strong earthquakes in the Vienna Basin are infrequent, historical records demonstrate that the regional seismic hazard remains relevant. This study presents a systematic evaluation of the seismic vulnerability of historic brick masonry buildings under varying structural configurations. The analysis is based on a detailed assessment of the structural system that defines key parameters of this building type. To capture the material variability typically observed in historic masonry, an extensive in-situ testing campaign was conducted on more than 200 URM buildings across Vienna, comprising over 2000 sampling locations. Non-linear static analyses (pushover) were performed using the 3Muri software on a representative reference case study building reflecting the typical structural characteristics of Viennese URM structures. A parametric study was conducted to investigate the influence of building height, masonry quality and floor configuration on the seismic performance of these historic buildings. This approach enables a targeted evaluation of structural uncertainty and a comprehensive assessment across a wide range of configurations. Further, fragility curves were derived to quantify the effect of each parameter on the probability of exceeding specific damage thresholds. The results confirm that low masonry quality and increased building height significantly amplify seismic vulnerability of historic URM buildings, whereas typical variations in floor configurations have only minor impact. These findings emphasise the importance of robust on-site experimental investigations to accurately characterise material properties and thereby enhance the reliability of vulnerability assessments. Moreover, the study highlights the limitations of simplified typology-based approaches and provides a solid basis for improved risk evaluation, retrofit prioritisation and seismic mitigation strategies.