Editorial
The use of steel and composites structures for seismic resistant building has always been a fundamental topic of seismic engineering. During the last Italian Conference of Steel Structures – CTA 2019, held in Bologna, a great part of the conference proceedings was focused on seismic issues regarding the design and evaluation of seismic performances in new buildings and the use of steel for the retrofitting of existing buildings. Steel construction in seismic areas provides many advantages as the weight reduction with a consequent reduction in seismic actions demand. In addition, metalic members are usually able to develop wide and stable hysteresis loops under seismic loadings, thus affecting the global ductility of buildings [Chao et al., 2019; Mitsui et al., 2018; Montuori et al., 2020; Piluso et al., 2019a; Castaldo et al.; 2017a; 2017b] whose is of paramount importance for the correct evaluation of the building capacity [Giordano et al., 2017; Chisari et al., 2017; Montuori et al. 2019a]. Moment resisting frames behavior under seismic loadings can be strongly affected by the degradation phenomena occurring in dissipative zones [Bernuzzi et al., 2018; Bernuzzi et al., 2019; Dell’Aglio et al., 2017; Ferraioli et al. 2018a; 2018b; Sandoli et al., 2019; Pengfei et al., 2019; Wang et al., 2019]. Moment Resisting Frames are usually cheaper than other steel typologies and assures an adequate seismic dissipation, provided that, connections are appropriately detailed and able to support the required strength and behaving as rigid connections [Tartaglia et al., 2018b; 2019; D’Aniello et al., 2017; Tenchini et al., 2018, Xu et al., 2018]. However, Moment Resisting Frames could not be used for high-rise buildings because of their high deformability that makes this structural typology very sensitive against serviceability and second order effects [Tartaglia et al., 2018a; 2018c; Montuori et al., 2019b], therefore, braced frames or dual systems are preferred [Costanzo et al. 2017; Costanzo et al., 2018; Jia et al., 2019]. In the last years, also cold formed profiles are getting head in the seismic field, used not only as a system for the strengthening and retrofitting of existing buildings [Totter et al., 2018; Formisano et al., 2016; Barbagallo et al., 2020; Ferraioli et al., 2020; Di Lorenzo et al., 2020] or for pallet racks [Gabbianelli et al., 2017; Montuori et al., 2019b] but also as the main structural system of new buildings, [Poursadrollah et al., 2020; Monsef Ahmadi and De Matteis, 2020; Campiche et al. 2018; Fiorino et al., 2018; 2019; 2012; 2017a; 2017b; Landolfo et al., 2010] or as an innovative bracing system [De Matteis et al., 2018]. Other research fields regard the use of dissipative devices in place of traditional dissipative zones for both steel structures and composites structures [Lemos et al. 2018; Latour et al. 2018; Titirla et al., 2017; Di Lauro et al., 2019; Piluso et al., 2019b; Nastri et al., 2019; Farzampour et al., 2019; Colajanni et al., 2020]. The use of these devices, properly located in points where the high displacement demand is expected allow the structure to remain in service also after the seismic event and an adequate reparability, benefit the maintenance costs. From the other side, the use of base seismic isolation remains a useful strategy to limit the plastic excursion and the structural damage [Avossa et al., 2017; Fraternali et al., 2018; Palazzo and Ferrentino, 2019]. However, the attentions of the research and many efforts are focused on designing and retrofitting buildings showing, after a seismicevent, the chance to exhibit a residual drift compatible with a convenient reparability cost.