Shear tests were conducted on screwed joints with decayed main members, and the degradation of shear performance of screwed joints by wood decay was investigated. The differences between decayed and control specimens in yield load (Py), and maximum load (Pmax) were both significant at the 1% level, while the difference in the initial stiffness (Ks) was not significant at the 5% level. The extent of decay was evaluated through Pilodyn penetration depth and the decay depth. Pilodyn penetration depth had no significant relationships with Ks, Py, or Pmax of screwed joints. It is inferred that no significant relationship was found between Pilodyn penetration depth and the strength properties because the range of the measured Pilodyn penetration depth was narrow (16–23.5 mm). The decay depth had a significant inverse correlation with Ks of the decayed specimens. There was no significant relationship between the decay depth and Py, or Pmax. Multiple regression analysis was conducted on Ks, Py, and Pmax using the decay depth and sound wood density (WDh) as 2 explanatory variables. The multiple regression of Ks, Py, and Pmax on the decay depth and WDh were significant at the 1%, 5%, and 1% level, respectively. Ks, Py, and Pmax are inferred to be determined by both the decay depth and WDh. The strength properties of screwed joints with one screw obtained in this study were compared with those of screwed joints with seven screws obtained in a previous study. The difference between Ks, Py, and Pmax of the screwed joints with one screw and those of the screwed joints with seven screws was not significant at the 5% level. It is inferred that shear performance of screw joints with multiple screws are sufficiently estimated from those of screw joints with one screw by simply multiplying the strength properties, even if the main members were decayed.

中文翻译：

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木材腐烂导致螺纹接头的剪切性能下降

对主要构件已腐烂的螺纹接头进行了剪切试验，并研究了木材腐烂对螺纹接头的剪切性能的影响。衰减试样与对照试样之间的屈服荷载（Py）和最大荷载（Pmax）的差异在1％的水平上均显着，而初始刚度（Ks）的差异在5％的水平上不显着。衰减的程度通过Pilodyn穿透深度和衰减深度进行评估。Pilodyn穿透深度与螺纹接头的Ks，Py或Pmax没有明显关系。可以推断出，在Pilodyn穿透深度与强度特性之间没有发现显着关系，因为测量的Pilodyn穿透深度的范围很窄（16–23.5 mm）。衰变深度与衰变样本的Ks呈显着反相关。衰减深度与Py或Pmax之间没有显着关系。使用衰减深度和木质密度（WDh）作为2个解释变量，对Ks，Py和Pmax进行了多元回归分析。Ks，Py和Pmax在衰减深度和WDh上的多元回归分别在1％，5％和1％的水平上显着。推断Ks，Py和Pmax由衰减深度和WDh决定。比较了本研究中获得的带有一个螺钉的螺纹接头的强度特性与先前研究中获得的具有七个螺钉的螺纹接头的强度特性。在5％的水平下，一个螺钉的螺纹接头与七个螺钉的螺纹接头的Ks，Py和Pmax之间的差异不显着。