AN AGING TEST OF NAILED TIMBER JOINTS WITH STRUCTURAL WOODEN PANELS

Strengths of wooden shear walls with structural wooden panels are affe cted mainly by the strengths of nailed joints between the panels and f rame members. Nailed joints with structural wooden panels, however, ha ve the risk of being impaired in their lateral resistance by aging par ticularly when exposed to moisture. This means that we must evaluate t his strength impairment to make sure of the structural safety of light frame timber structures through their service intervals. An appropria te single shear test of the nailed timber joints with structural woode n panels was investigated in this study. Oriented strand board (OSB) w as used as the test material. Strips of OSB were nailed onto small Dou glas-fir blocks with CN50 nails. Assembled test specimens were boiled and soaked in water according to the standard testing method JIS A 590 8 which is an accelerated aging test for structural wooden panels. JIS A 5908 provides that specimens must be tested immediately after soaki ng to avoid recovery of the specimen properties. This testing way, how ever, seems not to be appropriate for single shear tests of nailed spe cimens because the swelling of the wooden panels and timber members ma y result in high initial stiffness of the specimens due to strong inte rlayer contacts which prevents the exact evaluation of strength impair ment. To determine the most appropriate testing conditions, nailed joi nt specimens boiled and soaked in water according to JIS A 5908 were l eft in an irregular room condition for 0, 24, 48, 72, 96 or 120 hours. Then the specimens were tested, and their maximum lateral resistance and slip moduli were compared with each other. Test results showed tha t it was better to test the specimens after leaving them so that the w ooden panels would be dried to allow narrow gaps between the panels an d the timber members which avoided initial frictions between them.