Failure of industrial structures induced by the Emilia (Italy) 2012 earthquakes

At the end of May 2012, a seismic sequence struck the Emilia Region of Northern Italy, with two main events of local magnitude M-L. 5.9 and 5.8. The area affected is characterised by a high density of industrial buildings and its seismicity has been codified only recently. Given these conditions, there have been many structural failures. In this study, damage observed during field surveys is presented focusing on production plants. The interpretation of the structural performance is carried out recognising seven main types of damage related to: column base, short column failure, column top, shed beam, roof element, cladding/infill panel, and steel stand. These failures are compared with behaviours observed in the L'Aquila (central Italy), earthquake of 2009, with provisions compulsory at the time of the construction and with the current Italian seismic code. Some of the damage types, such as the formation of a plastic hinge at the base of a column and the unseating of the beam end from the column support, are interpreted by means of non-linear dynamic analyses on plane models representing typical configurations for such buildings. The contact between column and beam is modelled with either a pin or a friction connection. The analyses highlight the directionality of damage, the relevance of the vertical component of earthquake excitation, and the significant inelastic rotation induced in the columns. Finally, recommendations are made to improve the seismic behaviour of these types of structures. (C) 2013 Elsevier Ltd. All rights reserved.