Behavior factor of concrete portal frames with dissipative devices based on carbon-wrapped steel tubes
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Behavior factor of concrete portal frames with dissipative devices based on carbon‑wrapped steel tubes Andrea Vittorio Pollini1 · Nicola Buratti1 · Claudio Mazzotti1 Received: 11 October 2019 / Accepted: 7 October 2020 © The Author(s) 2020
Abstract The key element characterizing the seismic vulnerability of existing prefabricated RC structures, not designed for earthquake actions, are friction-based connections between structural members; mainly those between beams and columns and beams and roofing beams. The paper discusses the effectiveness of dissipative connectors made of carbon wrapped steel tubes. In particular, it presents the results of Incremental Dynamic Analyses on portal frames, aimed at evaluating behavior factor values to be used in design. A simplified formula for estimating the behavior factor is also proposed. Results of nonlinear IDAs suggest that the introduction of these dissipative devices in friction-based beam-column joints provides an effective connection between structural members and, in addition, reduces the forces transmitted to columns, improving the seismic behavior of the entire structure. Keywords Precast RC buildings · Friction connections · Dissipative device · Behavior factor · Seismic retrofitting
1 Introduction Precast reinforced concrete (RC) structures are widely used in many countries for one-story industrial buildings such as warehouses and factories. These structures, when designed and built without seismic-design criteria, have exhibited very high seismic vulnerability (Demartino et al. 2018), as highlighted by the 2012 Emilia earthquakes (Belleri et al. 2015; Savoia et al. 2017; Buratti et al. 2017). Considering their economic importance (Rossi et al. 2019), reducing their seismic vulnerability and, in general, the related losses in case of earthquakes, is of primary importance. Most of the partial- and full-collapses observed during past seismic events were caused by the absence of effective mechanical connectors between structural elements, in fact, friction-based connections were widespread (Bournas et al. 2013; Liberatore et al. 2013; Magliulo et al. 2014; Belleri et al. 2015; Babič and Dolšek 2016; Savoia * Nicola Buratti [email protected] 1
Department of Civil, Chemical, Environmental and Materials Engineering (DICAM), Alma Mater Studiorum - University of Bologna, Bologna, Italy
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Vol.:(0123456789)
Bulletin of Earthquake Engineering
et al. 2017; Demartino et al. 2018; Titi et al. 2018). The vulnerability of structures with this type of connections has been confirmed also by numerical simulations. Biondini et al. (2013a) analyzed the behavior under earthquake loads of friction-based connections by means of incremental time-history analyses. In particular, they investigated the influence of different values of the friction coefficient and of vertical of groundmotions. Titi et al. (2018) found that dry beam-column connections are associated to large relative displacements, which may lead to structural collapse, and that this condition is mo
