Effect of duration of load on shear performance of wood parallel to the grain direction using tensile shear testing

High-strength joints are increasingly used in timber structures to take advantage of the shear properties of wood. Therefore, understanding the long-term shear performance is essential. In this study, the long-term shear behavior of timber was evaluated using the tensile-shear test method. A duration of load (DOL) test was conducted to assess shear performance parallel to the grain under sustained loading. The test was carried out at loading levels ranging from 70% to 90%. The obtained strength modification factors as well as duration of load coefficients were greater than those specified in the current Japanese timber design standards, indicating that the code-specified values are conservative. In other words, the existing provisions ensure safety margins relative to the actual performance observed in the test. These results satisfy the requirements of the Japanese design code and are considered applicable to international design frame works, demonstrating the global relevance of the findings. The results indicate that the deformation at failure tends to converge at approximately 0.3 mm. A correlation was observed between deformation and environmental conditions, with the specimens loaded in April (n = 2) demonstrating greater deformation than the loaded in October (n = 4). The strength modification factor was determined to be 0.67, which is considered a safe value compared to the current standard of 0.55. This result is consistent with values reported in the previous study involving creep limit test study.