Seismic behaviour of curtain wall facades : a comparison between experimental mock up test and finite element method analysis

The present work is the result of a six months internship period at Permasteelisa S.p.a., a company specialized in design, production and manufacturing of curtain walls. Thanks to its laboratory facility and engineering offices, this study could have been carried out. In the first part an introduction about seismic phenomena and curtain wall façade is present. The most important criteria and features to be considered in the evaluation of the seismic behaviour of this “non-structural” element are reported. It is also fundamental the recognizing of the displacement applied to the façade, the “inter-storey drift”, as the worst load induced by an earthquake to a curtain wall, compared to forces and accelerations resulting from the same seismic event. After a comparison between the main National Regulations, Japanese JASS14 Standard has been chosen as reference. The following chapters describe the two different methods utilized: an experimental performance mock-up test, thanks to the use of Permasteelisa facility and its “seismic beam”, and a theoretical FEM modelling, through the use of the FEM software Straus7. A comparison between the results of the two different methods has been carried out: in a quantitative manner, in terms of displacements recorded during experimental tests and resulted from the FEM model solving; in a qualitative manner, through global considerations of the physical phenomena occurred during the experimental phase and, most of all, through the study of the FEM model outputs, primarily the stress distribution of every component. The results show that the considered unitized and panellized façade (structurally sealed system) behaves optimally during an earthquake, whichever its intensity could be, satisfying all the JASS14 standard requirements also thanks to the bearing phenomena of the alignment screw during the hardest test cycle. The FEM model can represent at the same time an important and complementary tool in the seismic design of a façade, but has to be improved and refined with the addition of the friction contribute. Anyway it offers the possibility to recognise stress values distribution and concentration points of every unit component.