Relationship between Embedment and Compressive Properties with Grain Direction of Hardwood Species

In general, softwoods are used as the main structural material for wooden structures, while hardwoods are less used. Some hardwoods show superior mechanical performance due to the high density about 1.0 x 103 kg/m3. Therefore, the utilizing hardwoods as structural materials are supposed to more flexible structural design proposals. Studies on the mechanical performance of hardwoods for structural design are not enough, especially as an embedment performance. In this study, it was conducted embedment and compression tests related to the joint performance of wooden structures using three species of hardwoods (Ulin, Buna, and Kuri) and a softwood (Sugi) to investigate the effects of strength performances such as density and woody structure. As a result, hardwoods with higher density showed higher strength performance. Embedment strength relative to compressive strength was 0.94 to 1.49 times higher in the direction parallel to the grain and 3.46 to 5.08 times higher in the direction perpendicular to the grain. About embedment strength, the ring-porous wood, Kuri, showed a similar trend (TR≒RT, TL≒RL) to that of a softwood, Sugi, while the diffuse-porous wood, Ulin and Buna, showed different trends (RT<TR, TL>RL).