自攻螺絲木構造接點的剪力行為與解析公式驗證

Shear Behaviour and Associated Analytic Formula for Timber Joint Composed of Self-Tapping Screw

葉玉祥(Yu-Hsiang Yeh) ； 葉衣祺(Yi-Chi Yeh) ； 游蕙安(Hui-An Yu) ； 陳怡秀(Yi-Hsiu Chen)

《建築學報》 118_S期：木構造專刊 (2021/12) Pp. 15-31

https://doi.org/10.53106/101632122021120118008

摘要

本研究主要探討木構造接點的剪力行為，其中，接點係由國產材組成並採自攻螺絲作為橫貫緊固件，透過剪力試驗評估接點的抗剪強度、韌性、及破壞模式，測出的剪力強度將拿來跟Eurocode 5的計算結果比較，藉以檢討公式之於國產建材的適用性。首先，本研究篩選適合用於建築結構的國產材和自攻螺絲，用以製作接點試體。國產材包含針葉木結構材福杉、柳杉、和屬於闊葉木的相思樹，自攻螺絲為台灣製造商代工的產品，挑選5種常用而細部處理略有不同的螺絲。以這些參數為基礎，共規劃16種接點，每種接點有9個試體，計144個剪力試體。剪力試驗的結果顯示，樹種會影響接點的剪力行為甚鉅，相思樹由於有較高的密度，因此其承載力與韌性都明顯比柳杉、福杉來得大。使用螺紋間距3mm的自攻螺絲的接點，其剪力強度和韌性分別比使用5mm螺距的試體高了10%、7%。使用全牙自攻螺絲鎖固的接點，其剪力強度與韌性也比半牙螺絲分別高出9%、7%。在使用墊片的情況下，接點的剪力強度與韌性皆可提升約7%。相較之下，鑽尾形式對於接點力學行為的影響較小。比較實驗值和Eurocode 5的計算結果後發現，Eurocode 5的評估結果偏保守，儘管仍有調適的空間以兼顧安全性與經濟性，這套評估方法可適用於國產建材並確保足夠的安全係數。

關鍵字

木構造 ； 接點 ； 自攻螺絲 ； 剪力行為 ； Eurocode 5

並列摘要

This study is focused on the shear behaviour of dowel-type timber joint composed of domestic wood and self-tapping screw. A series of shear test is intended for evaluating the shear capacity of timber connections. Then, the testing results are compared to the analytic values based on Eurocode 5' formula. The comparison contributes to verify the feasibility of the formula for domestic materials, including wood and screw. This study selects viable timber and self-tapping screw to manufacture various timber joints. The wood comprises softwood and hardwood for structural purposes, while the self-tapping screw consists of 5 different profiles in terms of screws' tailing and threading. Depending on these parameters, the shear test includes 16 types of timber joints and each type consists of 9 specimens. The testing results demonstrate that the species of wood influence the shear behaviour significantly. With greater density, the hardwood reveals higher capacity and ductility compared to softwood. Thread's spacing and the threading length influence joints' shear behaviour as well. The self-tapping screw with 3mm spacing of the thread increase the ultimate shear strength and ductility by 9% and 7%, respectively, compared to the specimens with 5mm-spacing screw. When applying fully threaded screw, the joints exhibit 9% higher shear capacity and 7% greater ductility than those with half-threaded screws do. According to the comparison between testing and analytic results, Eurocode 5 method conservatively predicts the joints' capacity. Although the formula may need further modification for Taiwanese materials, the calculation results ensure considerable safety margin for timber joints.

並列關鍵字

Timber Construction ； Joint ； Self-tapping Screw ； Shear Behaviour ； Eurocode 5

參考文獻

CNS 453木材抗壓試驗法（2013）。中華民國國家標準。臺北市：經濟部標準檢驗局。

葉民權，林玉麗，宋雲煒（2018）。結構用自攻螺絲接合之集成材雙剪抵抗性能評估。台灣林業科學，33(2)，41-61。

ASTM F1575-17. (2017). Standard Test Method for Determining Bending Yield Moment of Nails. West Conshohocken, USA: ASTM International.

ASTM D1761-12 (2012). Standard Test Methods for Mechanical Fasteners in Wood. West Conshohocken, USA: ASTM International.

Bejtka, I., & Blaß, H. J. (2005). Self-tapping screws as reinforcements in connections with dowel-type fasteners. International Council for Building Research and Innovation Working, 18(38), 38-7-4.