PUSH-OUT TESTS ON TIMBER-TO-TIMBER COMPOSITE (TTC) SYSTEMS MADE OF HARDWOOD

This paper presents the experimental results of mechanical test on fully threaded inclined screws when combined with different types of hardwood. Push-out specimens with symmetrical configuration were realized using glulam beams and boards made of three different species of Italian hardwood such beech, chestnut and beech-silver fir which constituted respectively the central and side members of the samples. Short term tested under quasi-static monotonic loading were carried out according to EN 26891. The main aim was to define the fasteners' stiffness, strength, static ductility and failure modes and so, to assess their goodness for the timber-to-timber composite (TTC) floor use. Outcomes are presented and discussed. Theoretical models proposed in literature were adopted to estimate the ultimate force and slip modulus to be compared with experimental results. Screws in hybrid beech-silver fir demonstrated significantly higher ultimate load, stiffness, and yield force than those in homogeneous beech and chestnut. The comparison with theoretical models highlighted an overall underestimation of load bearing forces and an overestimate of the slip modulus for fully hardwood components.