抄録
Mechanical properties of timber joints with metal plate connectors have been tested so far mainly by static loading. Works on fatigue properties of the joints subjected to cyclic loading, which are needed for determining safe design loads and for predicting the safe service life of the joints, are scarce and the effect of moisture cycling on the fatigue properties of the joints has not been clarified at all.
Rotating bending fatigue tests were therefore carried out on the timber joints of air-dried, water-saturated or moisture-cycled specimens. The effects of moisture content and moisture cycling on the fatigue properties of the joints were discussed with considering the failure modes of the joints and the strain distribution in the metal plate connector.
The results obtained are as follows;
(1) The relationship between the applied bending moment and the cycles to failure was expressed as a single continuous curve. The fatigue limit of air-dried and water-saturated specimens are 9% and 11% of the static strength, respectively.
(2) The failure modes of joints in fatigue tests could be divided into three categories. All teeth were pulled out of the wood block at relatively high moment levels, but they were sheared off at the root of teeth at relatively low moment levels. At intermediate moment levels, some were pulled out and the rest were sheared off.
(3) The fatigue strength of the joints was much influenced by the pre-treatments of moisture cycling, while the static strength was rather insensitive to the treatments.
