Compressive behavior of wood contact with mortar and epoxy resin adhesives

In recent years, researchers and engineers have developed a wide range of connection systems between wood and other materials, such as concrete and steel. However, the mechanical behavior of the surfaces where wood meets these materials is yet to be understood. In wood, low-stiffness areas called damage zones form near end grains, when compressed parallel to the grain. These low-stiffness areas may come in contact with various materials; therefore, understanding the behavior of the damage zones with various materials is important. This paper describes the results and analysis of experimental tests conducted on 130 specimens compressed parallel to the grain, to examine the compression behavior when the low-stiffness areas of glulam (Japanese cedar and Japanese larch) come in contact with mortar, epoxy adhesives, and steel. Compared with specimens joined with steels, the specimens joined with mortar had lower strength and stiffness, whereas those with epoxy structural adhesives had higher or almost equivalent strength and stiffness. Additionally, the specimens joined with mortar had the most significant strain in the damage zone, followed by those with steel loading plates and those with epoxy structural adhesives. These results suggest that using mortar as a contact material has a detrimental effect on the strength and stiffness of glulam. In contrast, the use of epoxy structural adhesives can improve the stiffness of glulam by mitigating the effects of the damage zone.