Experimental tests on dissipative cladding connection systems of precast structures

This paper presents the main results of an experimental campaign carried out within the FP7-SME European research project SAFECLADDING devoted to the improvement of the seismic performance of precast structures with cladding panels. The beneficial effects of dissipative cladding connection systems in providing additional structural damping through energy dissipation mechanisms, mainly based on plasticity and friction, are investigated. Different types of connectors are considered, including a panel-to-column and two panel-to-panel connection devices. The panel to-column device is designed for horizontal panels and consists of a steel plate folded at right-angle along three lines to get a W-shaped profile. In this way, the dissipative connection system allows to achieve stiffness and strength against out-of-plane loading, as well as flexibility and ductility to accommodate in-plane panel-to-structure relative displacements. The panel-to-panel connectors are friction-based or plasticity-based devices made by steel plates inserted into appropriate recesses within the joints in between vertical or horizontal panels. If the panels are connected to the frame structure by means of statically determined schemes, the panel-to-panel dissipative connections make the whole façade much stiffer and integral part of the earthquake resisting system up to the force associated with the friction threshold or yielding of the devices. Cyclic experimental tests on both single dissipative connectors and structural sub assemblies consisting of two full scale panels have been performed at the Laboratorio Prove Materiali of Politecnico di Milano to investigate the hysteretic behavior of the devices considering different technological features, restraint conditions, and loading protocols. Cyclic and pseudo-dynamic experimental tests have also been performed at the European Laboratory for Structural Assessment of the Joint Research Centre of the European Commission on full scale prototypes of precast buildings with vertical or horizontal panels. The results of the experimental tests confirm the remarkable improvement of the seismic performance of precast structures based on the beneficial effects of dissipative cladding connections, which can provide suitable energy dissipation capacity and limit forces and displacements under earthquake excitation.