Structural monitoring of damaged cultural heritage buildings after the April 2009 Abruzzo earthquake

The 6th of April 2009 a major earthquake struck the central part of Italy, causing hundreds of casualties and devastating the historical city of L’Aquila and several small towns in the area. The toll in terms of structural damage was enormous, also considered that a vast amount of buildings was made of poorly arranged masonry composed by round pebbles, with mortar of scarce mechanical characteristics. In particular, the buildings belonging to cultural heritage were between the structures that suffered more from seismic damage. The first step in the process of reconstruction was to provide the minimum safety conditions to the structures, in order both to avoid the damage progression and to allow to proceed with the necessary successive strengthening or retrofitting intervention with adequate safety conditions. In this framework, structural monitoring was employed in emblematic buildings to control the damage progression or stationariness with reference to the already carried out stabilisation interventions, or to allow a safer workplace during the execution of the interventions, also evaluating the effectiveness of the used strengthening techniques. The paper presents the first results of two dynamic and static monitoring systems, installed in the St. Mark church – a heavily damaged church of the city centre, and in the Spanish Fortress (L'Aquila castle), installed after a first experimental investigation campaign carried out in September 2009.