Cross-laminated timber is a construction material with significant potential to realize multi-storey earthquake-resistant buildings, exploiting the lightness of timber and the high in-plane strength and stiffness of the shear-wall panels, conferred by cross lamination of massive boards. In such buildings, connections play a vital role to assure an optimal seismic performance. However, traditional connections, i.e., angle brackets and hold-downs, have well-known drawbacks: low dissipative capacity due cyclic deformation of fasteners with consequent wood embedment and possible brittle failures due to uncertainty of actual strength of fasteners and relative overstrength factors. The increasing diffusion of tall cross-laminated timber buildings in high-seismicity areas requires the development of new strategies to increase ductility and dissipative capacities and to improve the reliability of the ductile parts of the structure. Both these purposes can be achieved with the adoption of new connections with optimized cyclic behaviour and localization of deformation in a steel element, preventing damage to the timber panel. A new connection for cross-laminated timber structures named “X-bracket” has been designed and tested at the University of Padova; it works both in tension and shear and can be used as panel-to-panel or panel-to-foundation joint. The special “X” shape is optimized to assure high stiffness and diffused yielding of material, resulting in extraordinarily high ductility and dissipative capacities. Furthermore, the possibility of producing multiple elements from cutting of a mild steel plate with minimal waste of material assures low production costs. This Report presents main details of the X-bracket and summarizes the research activities from the initial design phase to the experimental validation, discussing results from numerical simulations and laboratory tests. Installation, anchoring to the panel and possibility of replacement after a strong earthquake are also addressed and supported by additional tests, to verify the reliable response and controlled overstrength of the X-bracket, in compliance with capacity design
