| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1995: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1994: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Research Abstract |
1. In the pre-stressed laminated timber deck bridge made of Japanese Cedar, Larch and Oak, the initial rod force dropped to about 15% losses after two years. This initial rod force is based on the assumption that 60% of the stress will be lost during the lifetime of the bridge as a result of stress relaxation of the timber laminations. One year after the construction, the full scale field tests were done under static truck loading. the test values of deflection at midspan for symmetric loads and eccentric loads were about 10% and 15% smaller than test results at the time of bridge construction.
2. To investigate the effects of time-related stress loss of rod force on deflection of the pre-stressed laminated timber deck bridge, the bending tests were done by using the model deck. In the condition that the initial rod force dropped to 60% losses, the effect on deflection was about 10%. Therefore, the initial uniform compressive stress required between the laminations made of Japanese Cedar at the time of bridge construction is about 5kgf/cm^2, and the test values of deflection of the pre-stressed laminated timber bridge for this stress condition were approximately coincident with the results of numerical solutions by the orthotropic plate theory.
3. The model tests were done by using the composite glulam timber grillage girder made of Japanese Cedar. In this system, two main girders and two deck panels were used, and deck panels were placed in the direction of bridge axis and stressed together with steel rods installed tothe direction of bridge width. In the condition that the initial rod force dropped to 60% losses, the effect on deflection was about 5%, and the initial uniform compressive stress required between the deck panels made of Japanese Cedar is about 3kgf/cm^2.
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