In-plane behaviour of lightweight façade systems installed in masonry and concrete under simulated seismic loading

The protection of ancillary elements is of paramount importance in earthquake engineering. During a seismic event, in fact, they may be subjected to severe loading conditions with high absolute accelerations and potential distortion due to building structure deformations. The loss of functionality and the collapse of some attached element, as lightweight façade systems, may even precede any damage to the structures. For such elements, a good design practice should always consider special detailing to accommodate imposed deformations with reliable connections to the structural parts. While for the former several ready-to-use technologies are available, fastening solutions still need additional research, particularly considering possible in-plane amplification due to the substructure layout. Within this context, an extensive experimental campaign was recently carried out to investigate the in-plane behaviour of lightweight façade systems under simulated seismic loading. The results of the experiments are presented in this paper, where full-scale mock-ups were installed in concrete, masonry, and a combination of the two, and then tested using a one-directional shaking table. The following variables are considered in the study: (i) the base-material, (ii) the angle bracket type, and (iii) the mass of the cladding panel. Results from full-scale dynamic tests are discussed focusing on the load redistribution at the fixing points and on the residual capacity of fastenings. Measured axial forces on the fasteners are compared with design methods demonstrating the need for a revision to cope with the effects of resonance. Finally, an analytical model for the in-plane behaviour of lightweight façades is presented and verified against the experimental results.