Long-term capacity of bolted joints loaded perpendicular to grain

The long-term tests consisted of three bolt configurations and three timber materials - solid timber, LVL and cross-veneered LVL. The DOL tests were made under cyclic humidity conditions and stepwise loading. The studied phenomenon in the tests was the splitting of the timber in the joints. The bolts showed rigid behaviour, i.e., they remained straight in the tests. The long-term behaviour is compared to the behaviour of the timber material tests where the duration of load behaviour of the strength factors that are decisive at failure was studied. The result form the DOL tests was that the behaviour is not worse on joints than on timber, when the failure mode of the joint is compared to the one that is the closest to similar on timber. This result means that the same strength reduction factor can be used for mechanical joints than for the used timber material. The basic problem lies in the assumption in Eurocode 5, which states that the DOL effect is the same for all stresses in timber. The major element, which decrease the time to failure in this kind of load is the moisture induced additional stressess.