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The potentiality of cold-formed steel structures (CFS) interms of lightness, rapid on-site erection and high structural performance is spreading the use of the technology in the most industrialized countries. In particular, the overall recognized capability to assure a good structural response in high seismic areas is allowing the adoption in some of the most conservative communities.On the other hand, despite the many ongoing research in different countries, the current seismic design codes are often inadequate if compared to the evolutionary process. In this context, the new British Force School (BFS) represents one of the first cold-formed steel structures realized in Italy and, therefore, it required a long and complex verification process. Indeed, the seismic performance at the global and local scale had to be verified during the construction phase. This paper focuses on the evaluation of lateral response of the sheathed cold-formed steel (SCFS) shear walls, which represent the seismic resisting system of this structural typology through the presentation and discussion of the experimental campaign carried out to support the design.

The seismic behavior of sheathed cold-formed steel (SCFS) structures is characterized by the lateral response of shear walls. Basically, if cold-formed steel (CFS) structures are designed according to the “sheathing-design” methodology, then the seismic behavior of shear walls is strongly influenced by the sheathing-to-frame connections response, characterized by a remarkable nonlinear response and a strong pinching of hysteresis loops. In this paper the results of an extensive parametric non linear dynamic analysis, carried out on one story buildings by means of incremental dynamic analysis (IDA), using an ad hoc model of the hysteresis response of SCFS shear walls, are presented. An extended number of wall configurations has been considered investigating several parameters such as sheathing panel typology, wall geometry, external screw spacing, seismic weight and soil type. Based on IDA results, three behavior factors have been defined, which take into account overstrength, ductility and both overstrength and ductility, respectively. Finally, a design nomograph for the seismic design of single-storey SCFS frame structures developed on the basis of non-linear dynamic analysis results is presented. This last aims to complete a proposal of a design methodology, already presented by the author in the last years.