Shear capacity assessment of steel-to-CLT connectors

In modern prefabricated wooden buildings, CLT elements (Cross Laminated Timber, also known as Xlam, CrossLam or BSP) are assembled into macro elements (e.g., walls and slabs) and anchored by means of steel brackets and fasteners. A wide variety of such elements, in the shape of nails, screws and bolts, has been used in the construction market in recent years. Both the novelty of the construction technique and the wide number of fastener types imply that the knowledge about timber (CLT) joints is still limited. Under seismic shocks, steel-to-timber joints can prevent timber panels from overturning but, due to their high stiffness and low ductility, seismic energy dissipation occurs by damaging the timber elements over the fastening area. Hence, the sizing of such joints is a key factor in the design of a timber building. To improve the knowledge on the behavior of fastened steel-to-timber joints an experimental campaign was carried out. The paper discusses the testing of steel-to-CLT specimens, at changing of fasteners (i) type (i.e., 60 mm-length Anker nails and screws) and (ii) number (i.e., 2, 10, 18). The research aimed at characterizing the strength and stiffness of the compound element and at estimating the potential redistribution of loads at increasing number of fasteners (i.e., group effect).