Abstract
Effects of various environmental conditions on mechanical properties of wooden I-beams with Todomatsu (Abies sachalinensis) lumber and Karamatsu (Larix kaempferi) plywood were investigated. Five types of degradation treatment were chosen in this study. Ten pairs of treated specimens and end-matched control specimens were used in each treatment. After the moisture absorption treatment, the bending properties, maximum shear force and partial bearing strength of the treated specimens were about 10% lower than those of the control specimens. However, the bending stiffness obtained from shear tests was about 20% lower because the shear modulus of plywood decreases with increasing moisture content. Meanwhile, the water immersion and preservative treatments deteriorated the mechanical properties slightly. This indicated that the deterioration by water absorption would recover when the raised moisture content returns to the normal state. The boiling and decompression-pressure treatments deteriorated the shear bearing force more significantly than the bending bearing force. Based on the shear test results, it was confirmed that the treatments would greatly affect the shear properties in the following order ; preservative, water immersion, moisture absorption, decompression-pressure and boiling treatment. The residual ratios of the mechanical properties, evaluated in this study, could be utilized as adjustment factors related to environmental conditions and quality control of adhesion processes.
