A proposal of high strength wooden nail for environmentally friendly building

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In this research, we investigate the possibilities of compressed wood or bamboo nails as fastener in house construction and its adaptability to automatic nailer. Wooden nails have some points of advantage as follows :1. It does not have to assort from wooden part when recycling or scraping.2. It can be cut by wood machinery together with wood flame or panels when reusing.3. It causes neither the stain by metal nor the damages by moisture condensation.4. It is enough light to have an advantage in withstand load and seismic-resistant design.Splitting bamboo culms into 12 to 16 pieces, alternatively orienting, to outer and inner directions, compressing them with adhesive resin, the curvature of the strips is bent into flat form. The bamboo strips restrain each other during compression, which achieved greater deformation without breakage. A wide bamboo flat board can be obtained.We could obtain high strength material more than 400Mpa in MOR at density of 1.45g/cm^3 by 53% compression of bamboo (Madake).Nail head is important to increase withdrawal resistance when the panels joint to the flame by nails. Thus, we try to shape the nail with offset head. Furthermore, it increases by recovery of compression at nail point after piercing through the base material resulting in the same effect as clenching.As a pre-treatment to separate the long vascular bundles sheath from bamboo strips, we have tried the alkali treatment, steaming, steam explosion, and their combinations. As an example of the results, density of the products was around 1.33-1.43g/cm^3. The MOE and MOR exceeded 40GPa and 400MPa, respectively.The higher stiffness, yield and max strength, but lower toughness can be observed in bamboo nail compared to steel common nail.