| Budget Amount *help |
¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 1996: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1995: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Research Abstract |
Hysteretic behavior of mechanical timber joints subjected to cyclic loading was analyzed theoretically. Stepwise linear analyzes based on the theory of a beam on an elastic foundation was adopted in this study. Load-slip relationships of Nailed timber joints with plywood side-members, which are popular in light frame timber construction, under cyclic loading particularly were analyzed in the first year. In the second year, cyclic load-slip relationships of drift-pinned joints with steel center webs, which are popular in heavy timber construction, were analyzed.
In the first year, mechanical properties of the nail, which were required to evaluate the elasto-plastic bending stiffness of the nail, was determined by tensile tests of the wire material of the nails. Bearing stiffness of the timber under a nail, which also is required, were determined by monotonic, semi-cyclic and cyclic bearing tests. In the bearing tests, nails were driven into thin wood bearing specimens without lead holes
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so that the nails initially are gripped tight which could simulate the actual initial condition of the nail. From these test results, a hysteresis loop model was proposed considering the loading direction to the grain, impairment of bearing stress due to cyclic loading. To verify the analyzes, single-shear tests of nailed specimens with timber main-members and plywood side-members were conducted. The load-slip curves analyzed with the hysteresis loop model obtained in this study showed good agreement with the experimental results.
In the second year, similar experimental and analytical procedures are traced for the analyzes of the load-slip relationships of drift-pinned joints. Elasto-plastic bending stiffness of the drift-pin was determined directly from the test results of pure bending tests. Bearing stiffness of the timber under a drift-pin was determined ordinary bearing tests. Cyclic tests of drift-pinned joints with steel center webs were done to verify the analyzes. The computing program made for nailed joints were modified for drift-pinned joints. Analytical results successfully fitted the experimental results. Less
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