The partial collapse of "Casa dello Studente" during L'Aquila 2009 earthquake

The seven-story RC building hosting a University dorm and named ‘‘Casa dello Studente’’, was built between 1965 and 1967 for a mixed use (residential/commercial). The building plan is subdivided in three ‘‘wings’’ connected through the stairwell, with a basement common to all the wings and a second underground level below the South wing. In 1979 the building was bought by the ‘‘Opera Universitaria’’ of the L’Aquila University, to be used as student house, and in 1982 became a property of the Abruzzo Region, in force of State and Region laws. A wide refurbishment intervention, not affecting the structural system, was performed during the years 1999–2002. During the April 6th 2009 L’Aquila (Italy) earthquake a partial collapse of the building took place, limited to the North wing. A first exam of this wing pointed out the occurrence of two distinct collapse zones: the failure of all columns at the ground floor, due to a soft/weak story mechanism, and that of three columns from the base to the top of the building. The aim of the studies here presented, that were performed for legal reasons, has been twofold: to explain the collapse mechanism and to determine the causes of the collapse. This second aim has been pursued with a multidisciplinary approach, investigating the material properties, the ground motion at the building site, the dynamic behavior of the building in its original configuration and after refurbishment. In the light of the design criteria adopted in 1965, a collapse explanation is proposed, compatible with all the experimental data coming from the analysis of damage in the part of building that survived the earthquake and allowing to determine the mechanical causes of the collapse itself.