The Spanish Fortress in l’Aquila: emergency actions, investigations and monitoring

The earthquake occurred on the 6th of April 2009 in the Abruzzo Region of Italy seriously hit the Cultural Heritage (C.H.) patrimony with major destructive effects on l’Aquila, a city of 70,000 inhabitants with the size and the historical and strategic importance of the capital of the Region. The emergency activities to protect the C.H. have been developed following two parallel levels: (i) damage survey and (ii) design and implementation of temporary safety measures. The organization of emergency actions was managed by a centralized structure, the so-called Function 15 “Protection of Cultural Heritage” directed by a Special Commissioner. The structure coordinated the on-site surveys of protected buildings and the design and implementation of temporary safety measures. Several Italian Universities during and after these first emergency actions were invited by the Commissioner to work on selected Case Histories: the aim was on the one hand to provide a first interpretation of the observed damages and on the other hand to define some guidelines for a higher level of investigation. In this paper the case study of the Spanish Fortress in L’Aquila supervised by the authors is reported with the description of the earthquake damages and the emergency intervention derived from the “Palaces template” [Ref. 1]. The emergency interventions were carried out in order to avoid progressive damages due to the following several aftershocks. The authors decided together with the officers of MiBAC (Ministry of C.H.) in L’Aquila to proceed with further on site investigations and monitoring. A series of non destructive and minor destructive testing were performed in the Spanish Fortress by the research groups of the Politecnico of Milan and the University of Padova in order to characterize and evaluate quantitatively and qualitatively the state of damage of the masonry structures (walls and pillars) and to identify the structural response of the most damaged wings of the building. The experimental campaigns included: (i) sonic pulse velocity tests, radar tests and thermography, (ii) single and double flat jack tests, (iii) dynamic identification tests. The ND tests were mainly aimed at defining the state of damage of the heavy pillars and of the transversal bearing walls on the ground floor and at designing the most effective strengthening interventions. Furthermore a permanent static and dynamic monitoring system was installed by the ISCR (Rome) and the University of Padova respectively in order to control the dynamic characteristics of the fortress, constantly verify the damage pattern of the structure and provide a step-by-step monitoring procedure during each phase of restoration.