Duration of Load Effect on Axially-Loaded Self-Tapping Screws Inserted Parallel to Grain in Soft- and Hardwood

The growing stock of deciduous tree species with high strength capacities predes-tines their application in plane and spatial frameworks and branched structures. Im-portant prerequisites therefore are economic and high-performing joint solutions. End-grain joints with self-tapping screws can be one efficient solution for such joints as they are highly optimised for axial loads and easy to apply. However, insufficient knowledge, singular test outcomes and fears concerning the duration of load (DoL) behaviour currently prevent economic joint solutions with self-tapping screws in-serted parallel to grain. Motivated by this apparent research gap, a project was initi-ated to investigate the DoL effect on the withdrawal capacity of in tension axially-loaded self-tapping screws inserted parallel to grain in soft- and hardwood species and products. Preliminary results gained after 2.25 years DoL investigations outline the necessity to harmonise test procedures also in respect to the time-to-failure. Considering this, the applicability of current DoL regulations in Eurocode 5 also for ax-ially-loaded self-tapping screws is demonstrated.