TECHNOLOGIES AND ENVIRONMENTAL BENEFITS TO REUSE TWO-BY-FOUR SALVAGEDLUMBERS

摘要

Demand for recycle changes reflecting the social and economical situations. Considering the change on the demand for resource utilization it is important to prepare different types of recycling methods and leave a chance to choose the best recycling method according to the situation of the society and the environment.Almost 50 years ago salvaged lumbers were commonly used as structural materials for the post and beam single detached houses in Japan. If we can tell the strength properties of the salvaged lumbers we can use them as structural elements for the wooden houses. And if we can take a little more care and spent more time on deconstruction we can produce higher quality salvaged lumbers from the deconstruction site.On the other hand recycling and reusing wood based materials will help keep storing carbon as materials. This will work as to reduce carbon discharge caused by burning the materials and to reduce the movement toward global warming.The purpose of this study is to prepare technical information for the salvaged lumbers and draft a standard for the reclaimed two-by-four lumbers. Almost 1000 pieces of salvaged lumbers were tested for their visual grades, structural defects and physical characteristics. And almost 300 pieces of salvaged lumbers were tested for their tension strength properties.The test results can be summarized as follows.(1) The strength value for the salvaged lumbers was 4.76(N/mm~2). The calculated design value for the salvaged lumbers was almost equivalent to that of the grade "Standard" and was lower than their original grade "No.2".(2) The strength value of the salvaged lumbers that was visually graded as S-P-F No.2 was 6.20(N/mm~2) and was 1.5(N/mm~2) higher than the strength values calculated for the group of all salvaged lumbers. But the yield ratio became to be 68.7% by selecting the lumbers.(3) The strength value of the salvaged lumbers that have MOE no less than 9.6(GPa) was 6.70(N/mm~2) and the yield ratio was 84%.(4) A better yield can be achieved by selecting salvaged lumbers by their MOE. The strength value of the lumbers that had MOE no less than 9.6(GPa) was equivalent to standard strength value stipulated for the S-P-F no.3 grade lumbers.