An investigation on the collapse sequence of an RC frame during L’Aquila 2009 earthquake

The partial collapse of a seven-story reinforced concrete building designed in 1965 is investigated starting from previous results. The building was hosting a university dorm, named “Casa dello Studente”, and suffered the partial collapse of one of its three wings during the April 6, 2009 earthquake of L’Aquila (Italy). Two distinct collapse zones were detected in the collapsed wing: a soft/weak story mechanism at the ground floor, and the failure of three columns along the height. In a previous study, encompassing only linear analyses, the lack of flexural strength of ground story columns was detected as the main cause of the collapse. Here non-linear static analyses of a refined numerical model of the structure, including the reinforcement data, allow for a better insight on the disproportionate effects that the partial soft-story collapse had. The results clarify the role of lack of shear strength of a beam on the collapse of the three columns.