Strength and Rigidity Performance of Laminated Members Using Small-Diameter Logs

Abstract

Abstract Korea and other countries have a high ratio of small-diameter logs in the harvested log volume. Hence, using these small-diameter logs as structural materials is an important issue. The lumber obtained from small-diameter logs generally has small cross-section dimensions and is mostly juvenile wood, resulting in inferior strength performance. In this research, a laminating process was developed for effective utilization of small-diameter logs as structural materials, and eight types of laminated beams and eight types of laminated columns were manufactured by the vertical and horizontal laminations with square cross-section timber. The laminated members were composed of laminated square timber obtained from small-diameter logs and were reinforced by square timber or lamina obtained from large-diameter logs. The laminated members were evaluated for their bending and axial compression performance. As a result, the beam exhibited an increase in bending Young's modulus of 63 percent and bending strength of 77 percent. Additionally, the column's axial compression performance indicated a positive effect on compression Young's modulus, where a 158 percent increase was found. Furthermore, when Johnson's equation was used to determine the critical stress, the value was close to the yield stress. In contrast, Euler's equation led to overestimation of the capacity as the slenderness ratio became smaller, which indicated that the application of Johnson's equation may be preferable. Therefore, a combination of small-diameter logs and large-diameter logs provided increased strength and rigidity performance, indicating the possibility of an effective use of small-diameter logs.