Effect of deformation rate on bearing properties of mechanical joints of LVL with a drift pin

Strength properties of most mechanical joints used in timber structures dep end on bearing performance of wood as a visco-elastic body. Thus, in order to examine the behavior of the joint, the effect of loading rate ur deforma tion rate should be considered. As the first step tu investigate the effect of deformation rate on bearing characteristics, we conducted embedment tests of a drift gin into laminated veneer lumber (LVL). Species used for the LVL were radiata pine (Pinus radiata D. Don.), Japanes e red pine (Pinus densiflora Sieb. et Zucc.) and grand fir (Abies grandis L indl.). Diameter of the drift pin was 12 mm. Loading type was monotonic ten sile, and deformation rates (embedding speed of the drift pin) were 0.05, 0 .5, 1, 5, 50 and 500 mm/min. Maximum bearing stress increased with increasing deformation rate except fo r Japanese red pine. Initial stiffness showed a tendency to have a minimum value at a certain rate. Deformation at maximum stress and total bearing en ergy showed a tendency to have a maximum value at a certain rate. Ratio of ductile bearing energy (bearing energy from deformation at maximum stress t o ultimate deformation) to total bearing energy was not influenced by the r ate. Maximum bearing stress decreased with increasing time to rupture.