Degradation of shear performance of screwed joints caused by wood decay

Rintaro Ueda,Takanobu Sasaki,Yoshihisa Sasaki,Kei Sawata,Ryuya Takanashi

doi:10.1186/s10086-020-01889-w

Rintaro Ueda, Takanobu Sasaki + Show 3 more

Open Access

https://doi.org/10.1186/s10086-020-01889-w

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Abstract

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.

Highlights

When degradation of wood occurs in wooden construction, the degraded wood member is reinforced or partly replaced
We have investigated the effects of wood decay on the shear performance of screwed joints
Pilodyn penetration depth had no significant relationships with Initial stiffness (Ks), Yield load (Py), or P-max

Summary

Introduction

When degradation of wood occurs in wooden construction, the degraded wood member is reinforced or partly replaced. The replacing of the timber might necessitate the disassembly of the wooden structure which is difficult, costly, and requires skills and knowledge. For these reasons, reinforcing is often preferred to repair the deteriorated wooden constructions. Information on the remaining strength capacity of joints with decayed wood is required because the strength capacity of joints often affect the structural performance of the construction. Some studies that evaluate the degradation of shear performance of nailed joints caused by wood decay have already been reported [8–10]

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