Timber Pins Connection: Reliability of Bolted Joints Design Rules

The use of timber pins in connecting timber elements is a valid alternative to the employment of metallic devices, and apart from being quite spread in prefabricated timber frames, it could be an efficient solution in the field of restoring timber structures. The design rules for pinned joints are universally based on Johansen’s theory, (European Yield Model), but their application to timber pegged connections still shows some unsolved problems, linked to: 1) dowel-bearing strength; 2) bending strength of the pin; 3) shear strength of the pin; 4) the feasibility of the fourth failure Mode of EYM. Many studies analysing one or more of those aspects can be found in literature, but there isn’t yet an analytical formulation alternative to this on which the EYM is based. Authors are carrying on an extended experimental research, trying to better understand the complex mode of failure of timber joints connected by timber pegs, and consequently improving design rules. A first phase has involved double shear plane joints of glulam fir connected by ash pins, varying thickness of jointed board, pointing out the role of bending strength. In a second step the role of dowel-bearing strength has been investigated, choosing as base material three wood essences with quite different densities. Now the final step of the whole research is presented: first of all, the role of pin shear strength has been studied; then all obtained results are employed in analyzing the behaviour of double shear plane joints with varying timber essences and its transposition in using design rules.