Seismic-resistant CFS walls braced with pre-tensioned UHS steel bars: Design and construction of a building mockup

The paper presents the design and the construction of a real mock-up two-story exhibition building having a load bearing cold-formed steel (CFS) structure, where the lateral force resisting system (LFRS) is represented by an innovative hybrid wall made of CFS studs and tracks laterally braced by ultra-high strength (UHS) steel pretensioned diagonal bars. The hybrid CFS wall represents the result of the Italian research project, named ECCELSA, aimed to develop a CFS LFRS wall capable to be used where high resistance capacity is required, as in the case of medium-to-high seismic areas or medium-rise buildings. From the design and construction point of view, the real mock-up building presented in this paper appears to best satisfy the high safety, durability and eco-efficiency standards required by the building construction market. In order to verify the effectiveness of the design procedure adopted, a refined numerical model was developed and validated against the experimental results obtained during the research project. The results of non-linear static analyses highlighted a structural overstrength and revealed the building ductility, mainly due to the hardening and ultimate elongation of the UHS bars, which had not been accounted for during the design phase.