Strength Properties of Sugi Timber-Joints with Metal Plate Connectors
Tomoyuki HAYASHI, Masahiko KARUBE, Masaki HARADA and Hirofumi IDO
Abstract: Gusset truss systems using metal plate connectors have been developed and are used in residential constructions in Japan. Several softwoods, such as SPF (Picea spp., Pinus spp., and Abies spp.) and White Spruce (Picea abies Karst), have been used as structural members of the systems. However, Sugi (Cryptomeria japonica D. Don), the most important species in Japan has not been used so far. To examine the feasibility of Sugi, tensile strength tests were made on Sugi timber joints with two kinds of metal plate connectors (GN80 and GNQ). Furthermore, full size bending tests of roof trusses composed of Sugi and GN80 were conducted to discuss the availability of current structural design method. Sugi joints showed lower maximum strength and toughness than SPF and White Spruce. However, it was found that Sugi had enough performance required for structural members. Coefficient of correlation between the density of wood and tensile strength of the joint was positive in any kinds of specimens, but most of them were less than 0.3. The current design method for plate size and truss members can be applied to the Sugi gusset trusses, though its estimation for deformation is rather conservative. Since the mechanical properties of Sugi vary with its cultivar, provenance, or other factors, such as the amounts of small knots, more experimental data should be accumulated to expand the practical applications. Key Words:Metal plate connector, Timber joint, Metal plate gusset truss, Sugi, Full size test