PSI - Issue 78

Franco Braga et al. / Procedia Structural Integrity 78 (2026) 2176–2183

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1. Introduction The earthquake of the night of August 24, 2016, the first event in the Central Italy sequence, shocked the town of Amatrice, causing devastation to buildings and a significant number of injuries and loss of life. The devastation observed following the event raised many questions, particularly regarding the exceptional nature and therefore severity of this specific earthquake. The presence of two accelerometer stations, one from the RAN network, called AMT, located at the western entrance to the town, below the "morphological terrace" of Amatrice, and one from the Civil Protection Department network, called AMTS, located inside the "Romolo Capranica" School, allowed for precise knowledge of the seismic signal that struck the town. Specifically, in this work, after defining the peculiar characteristics of the earthquake in question through analysis of the recordings from the previously described stations, a numerical model of one of the reinforced concrete twin buildings, located in P.zza Sagnotti 5,6, a few meters from the AMTS accelerometer station, was implemented. The analysis carried out on the model demonstrate the severity of the stresses on the load-bearing structures of these buildings which suffered a generalized collapse

caused by the 2016 earthquake. 2. Description of the buildings

The buildings analyzed were located in Amatrice (Rieti) in Piazza Sagnotti n.5 (building "B") and n.6 (building "A"), they were divided into a ground floor, three floors for residential use, a pitched roof. Fig. 1 shows the general plan of the town of Amatrice, identifying and positioning: i) the buildings in question; ii) the AMTS accelerometer station installed by the Department of Civil Protection (DPC) in the Romolo Capranica school, approximately 100 m away from the buildings in question; iii) the accelerometer station of the National Accelerometric Network (RAN) called AMT.

Fig. 1. General plan of the Municipality of Amatrice (Google Earth).

3. The event of 08.24.2016 3.1. “Near Fault” earthquakes

The earthquake in question, due to a hypocenter depth of less than 10km, is one of those already defined in the 90s by US codes (UBC-1997) as "near fault earthquakes". In the UBC (and in other international technical regulations) the treatment of this type of earthquakes is motivated by the fact that, the reduced depth of the hypocenter produces, in addition to a limited dissipation of energy due to the reduced power of the layers of soil crossed, a series of peculiar characteristics and a particular severity of the seismic actions that stress the structures on the surface. In detail, the characteristics of "near fault" earthquakes are the following: • Forward-directivity consisting in the fact that, if the failure front of the fault propagates towards the site under examination and the speed of advancement of the failure and the transmission speed of the shear waves are similar, there is an accumulation of several waves that determine a considerable impulsive motion in the direction orthogonal to the fault; this motion is characterized by high frequencies (Somerville et al., 1997; Braya & RodriguezMarek, 2004; Ghahari et al., 2010) whose effects on the