Physics-based seismic vulnerability assessment of aging building stocks at city scale

Earthquakes pose significant risks to urban areas, often leading to devastating economic losses and casualties. This paper aims to introduce YouSimulator, an innovative city-wide seismic damage simulation software, as a valuable platform for assessing urban resilience to earthquakes. Applied to Thessaloniki, Greece—a city with a notable seismic history as it was the first modern metropolitan area in Greece to be hit by a catastrophic earthquake—YouSimulator demonstrates its ability to quantify the functional integrity of urban areas by creating a digital twin of 1,252 buildings. The software consists of four key functional modules enabling automated modeling, seismic response calculations, comprehensive analysis of multi-degree-of-freedom responses and three-dimensional visualization of the seismic response. Utilizing parallel computing and high-performance algorithms, YouSimulator automates the assessment of building vulnerability, calculating a generalized damage index that categorizes buildings into five levels: free of damage, minor damage, moderate damage, severe damage, and destroyed/collapsed. The analysis reveals that Thessaloniki’s downtown performs satisfactorily under design earthquake scenarios, with no building collapses but a significant reduction in overall strength capacity of buildings. Notably, older pre-code reinforced concrete structures, which make up 96.3% of the building stock, exhibit high seismic vulnerability, highlighting the urgent need for retrofitting measures. Medium and tall buildings show increased susceptibility to severe damage, indicating a need for height-specific mitigation strategies. Additionally, pre-1959 buildings facing severe damage state should be targeted for structural interventions. Overall, this research validates YouSimulator for assessing urban seismic vulnerability and emphasizes the necessity of integrating detailed local seismic data into urban planning efforts to bolster resilience of cities against future earthquakes.