Applications of Operational Modal Analysis in Seismic Risk Assessment of an RC Building: A Case Study from Türkiye

It is evident that earthquakes can turn into disasters if buildings in affected areas are constructed without proper engineering. The February 6, 2023, Kahramanmaraş earthquakes of Türkiye impacted 14 million people across 11 cities and caused over 150 billion USD in damage. Assessing the structural safety of existing buildings is crucial to reducing earthquake risks. In this study, first phase of seismic risk assessment for an educational building in Yakutiye, Erzurum was conducted. Data was collected, a finite element model was created, and a theoretical modal analysis was performed. The theoretical fundamental vibration period of 1.220 seconds for the four-story structure was found to be high. To verify this, a dynamic identification study was carried out. Operational modal analysis, including sensor optimization, determined the in-situ fundamental vibration period as 0.241 seconds. The additional rooftop floor significantly affected the building’s modal behavior. The discrepancy between theoretical and experimental values was due to the omission of infill wall stiffness in the finite element model. Neglecting infill wall effects in seismic risk assessments may lead to incorrect results, underestimating seismic forces. The study found that the building could experience earthquake forces ~5 times higher than that of the theoretical estimation.