Tensile Strength Properties of Glued Laminated Wood and Laminated Veneer Lumber with Butt-Joints
Tomoyuki HAYASHI and Atsushi MIYATAKE
Abstract:Tensile strength tests were carried out on various glued laminated wood (GL) and laminated veneer lumber (LVL) with butt-joints (BJ), and size effects of the length of specimens were examined experimentally. In addition, laminating effects which improve strength properties were also examined on the GL. Species used for the specimens were sugi(Cryptomeria japonica D. Don), akamatsu(Pinus densiflora Sieb. Et Z.), and Douglas fir (Pseudotsuga menziesii Franco) for the GL, and akamatsu and radiata pine (Pinus Radiata D. Don)for the LVL.@In the case of GL, tensile strength(TS) decreased to 23.5% (sugi), 30. 9% (akamatsu), 18.2% (Douglas fir) of their raw materials. Size effect was evidently observed on the GL, and the reduction of TS by size effect was higher than that of the laminae. Coefficient of laminating effect (ratio of 5% lower extrusion limit after lamination to that of before lamination) on the TS of 2 ply laminated GL ranged from 1.84 to 2.47. In the case of LVL, the thickness of veneer affected on TS remarkably, and 15 ply type specimens composed of 3 mm thick veneer showed higher TS than 7 ply type specimens composed of 6 mm thick veneer. Size effect of LVL depended on the thickness of veneer. While 15 ply type specimen showed no size effect, TS of the 7 ply type specimen decreased with increasing the specimen length. Key Words:Tensile strength, Glued laminated wood, Laminated veneer lumber, Size effect, Laminating effect