Structural health monitoring for post-earthquake controls: Applications in l'Aquila

In the last decades structural health monitoring (SHM) has been increasingly applied in the study of Cultural Heritage (CH) buildings, as a key activity to improve the knowledge on their structural behavior and identify the presence/activation of possible damage mechanisms. This knowledge allows engineers to carry out with more confidence and only if necessary a strengthening intervention, and it helps to prevent the execution of intrusive repair works, if not justified by an experimentally demonstrated worsening of the structural conditions. The use of monitoring systems applied under ordinary conditions and installed on CH structures may allow to: (i) validate the functioning of the adopted structural models; (ii) identify ongoing damaging processes; (iii) validate the effectiveness of the strengthening interventions. In case of a seismic event, SHM can furthermore prove its usefulness in order to: (i) evaluate quantitatively the progression of the damage pattern, (ii) carry out effective and urgent interventions if an unsafe displacement patterns is recorded; (iii) define an early warning procedure for the safety of the workers employed in the strengthening interventions. Monitoring can also be effective when implemented on seriously damaged buildings, if the time schedule for the interventions is difficult to be a priori planned. In this framework, the authors designed and installed SHM systems on six representative and emblematic CH buildings in L'Aquila after the devastating earthquake occurred on the 6th of April 2009 in the Abruzzi Region. Two selected case studies (Spanish fortress and Civic tower) report the experience gained on the use of monitoring during the emergency activities after a seismic event. Monitoring and damage detection algorithms have been successfully applied to control the evolution of the seismic-induced damages and verify the effectiveness of the provisional interventions executed immediately after the earthquake.