Structural monitoring and earthquake early warning systems for the AHEPA hospital in Thessaloniki

This study aims at presenting the analyses of monitoring data that have been used in the context of structural monitoring and Earthquake Early Warning (EEW) for a hospital building in Thessaloniki. Permanent and temporary instrumentation arrays, implemented under the responsibility of Aristotle University of Thessaloniki (SDGEE-AUTH) in close cooperation with German Centre for Geosciences (GFZ) are presented. The ambient noise data recorded at the temporarily installed networks are used for the dynamic characterization of the building based on both vibrational and waveform approaches. Moreover, long-term ambient noise recordings from the permanent array installed within the hospital are used for the investigation of the daily and seasonal wandering of the building resonance frequencies related to environmental effects. The modal identification results are used in a comprehensive framework for the computation of the up-to-date fragility curves representing the actual structural state considering aging effects of the construction materials, possible pre-existing damages and changes in the geometry and mass distribution. The building-specific fragility functions are integrated into two independent EEW systems and rapid damage assessment approaches, namely the PRESTo software and an onsite EEW algorithm on the instruments of the permanent array, to provide the expected level of damage after strong ground shaking at the monitored building. The implemented monitoring networks and the developed operational tools can be used in the context of seismic risk mitigation and preparedness for structural safety assessment under earthquake loading.