A CASE STUDY OF COLLAPSE DURING THE 2009 L’AQUILA (ITALY) EARTHQUAKE

A number of masonry and reinforced concrete (RC) buildings suffered failure during the magnitude Mw 6.3 earthquake that struck the city of L’Aquila (Italy) on April 6 2009. Many of the RC buildings were designed and built between the late fifties and the early seventies. The partial collapse of the “Casa dello Studente” (Student House) building in L’Aquila, with its high death toll of eight students killed and one suffering serious injury, is paragdimatic on one hand of the possible fragility of reinforced concrete construction of that period, on the other hand of failure due to an adverse sequence of events. The legal authority appointed a forensic team, lead by the first author, for investigating the causes and the mechanism of the collapse. During a six-months period, the team had a unique chance to analyze in a thorough way the collapse causes. The joint efforts of the forensic team led to a complete explanation of the collapse and highlighted the sequence of missed opportu- nities that let this happen. Collapse took place within part of the North wing trough a twofold mechanism: a weak-story mechanism, which involved collapse of all the columns at the first story, and the complete collapse of three columns located close to the floor center. The two mechanisms were due to an initial design error, never discovered during the subsequent ren- ovations of the building, whose effects were adversely amplified by a non-structural fire-proof wall inserted in recent times to comply with fire safety requirements. This imposed unforeseen strength and ductility requirements on members not specifically designed for this. This paper presents some of the result of the studies that, not strictly necessary for legal reasons, were only performed after completing the report for the legal authority. Nonlinear analyses are adopted to highlight the role of each of the factors listed above which lead to the structural failure.