Self-tapping screws have the potential to reinforce timber elements. However, their application is restricted due to a lack of design guidance. Compared with fully threaded screws, partially threaded screws with a shorter thread length have less drive-in torque, enabling easier installation. This study showed that partially threaded screws are as effective as fully threaded screws in enhancing the mechanical properties of single-dowel timber connections with artificial cracks. A total of 120 embedment tests were conducted, using screws with two thread lengths (33% and 100%) on single-dowel connections. The connections were also prepared with three different widths of artificial crack to represent splitting of the wood due to moisture variation. The results showed that the screws with 33% thread length were as effective as screws with 100% thread length at reinforcing the connections when the crack width was 1.5 mm or 4.5 mm. However, for a crack width of 6 mm, the embedment strength of the connections reinforced with screws with a 33% thread length was significantly lower (about 15.7%) than the connections reinforced with screws with a 100% thread length. This research demonstrates the potential of using self-tapping screws with a partial thread to reinforce existing timber elements with cracks.

中文翻译：

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自攻螺钉作为带有人工裂缝的单销钉连接的加固

自攻螺钉有可能加固木材构件。然而，由于缺乏设计指导，它们的应用受到限制。与全螺纹螺钉相比，螺纹长度较短的半螺纹螺钉具有更小的拧入扭矩，从而使安装更容易。这项研究表明，部分螺纹螺钉与全螺纹螺钉一样有效，可以提高具有人工裂缝的单榫木材连接的机械性能。总共进行了 120 次嵌入测试，使用具有两种螺纹长度（33% 和 100%）的螺钉连接单销钉。这些连接还准备了三种不同宽度的人工裂缝，以表示由于水分变化导致的木材开裂。结果表明，当裂缝宽度为 1.5 mm 或 4.5 mm 时，螺纹长度为 33% 的螺钉与螺纹长度为 100% 的螺钉一样有效地加固连接。然而，对于 6 mm 的裂缝宽度，使用螺纹长度为 33% 的螺钉加固连接的嵌入强度明显低于使用螺纹长度为 100% 的螺钉加固连接的嵌入强度（约 15.7%）。这项研究展示了使用带有部分螺纹的自攻螺钉来加固现有裂缝木材构件的潜力。7%) 比用 100% 螺纹长度的螺钉加固的连接。这项研究展示了使用带有部分螺纹的自攻螺钉来加固现有裂缝木材构件的潜力。7%) 比用 100% 螺纹长度的螺钉加固的连接。这项研究展示了使用带有部分螺纹的自攻螺钉来加固现有裂缝木材构件的潜力。