TREMA Project: Experimental evaluation of the seismic performance of a R/C ¼ scaled model upgraded with the DIS-CAM system.

A new system for the seismic retrofit of R/C frames has been tested within an extensive experimental investigation on shaking table, carried out for the TREMA project (Technologies for the Reduction of seismic Effects on Architectural Manufacts) [5]. The system has been applied to a 3D reinforced concrete model. The model was a ¼ scaled frame, with three stories, two and one bay in the two directions respectively, originally designed for gravity loads only [5]. It was previously tested, first with base isolation and then in the fixed base configuration, up to being severely damaged. It was repaired, by restoring concrete of failed joints at the 2nd floor with high strength mortar and by injecting cracks with epoxy resin. It was then upgraded with the DIS-CAM system. This system is an improvement of the CAM system described in [4]. The original CAM system provides confinement to columns using steel angles and steel ribbons, while the new improvement is based on the addition of special steel connecting energy dissipating elements at the beam-column joints. The retrofit determines an increase of strength and ductility of single elements and joints, as well as an increase of the overall ductility, if it is designed according to the capacity design criterion forcing the structure to develop a strong column-weak beam mechanism. The experimental tests were carried out with the two simultaneous horizontal components of the Umbria-Marche 1997 earthquake, up to 0.52g normalised peak value (NPA as defined in [5]) of the horizontal table acceleration and with the three simultaneous components of the near-fault Northridge Rinaldi record, up to 0.84g horizontal NPA. In the paper the application of the DIS-CAM system is described, along with the criteria for the design of the upgrading intervention made on the damaged model. The main results of the experimental tests are reported, in terms of interstory drift, accelerations and period variation during the sequence of tests. The behaviour of the model under the different seismic excitation is discussed and the local and global damage is carefully analysed.