主鋼筋對RC無腹筋矩形梁剪力行為之影響

The Effect of Main Reinforcements for Shear Behavior of The Rectangular RC Beams without Stirrups

林育民(Yu-Min Lin)

指導教授 ： 林至聰

國立臺北科技大學/工程學院/土木與防災研究所/碩士(2008年)

https://doi.org/10.6841/NTUT.2008.00469

摘要

目前國內對RC規範的訂定仍以ACI (American Concrete Institute) 規範系統為主要依據，而探討RC結構的破壞模式時可以發現，撓曲的破壞行為富有延展性，具有延遲預警的效果，反之剪力的破壞則常發生於頃刻之間，往往造成重大傷亡產生，因此避免剪力破壞的發生在結構設計上仍是項重要的課題。然而造成剪力行為的因素較複雜，且規範對Vc過於低估其主鋼筋的影響而有過於保守之嫌，故仍有許多值得檢討的空間，而目前對於剪力行為的研究已稍具規模，但相對於撓曲行為仍顯得較為模糊，因此相關研究還有待更多試驗的佐證。
　　而為探究主鋼筋對剪力行為的影響差異，本研究製作18cm×22cm×135cm之RC無腹筋矩形梁試體18組共36根，以六種主筋配置及170kg/cm2、245kg/cm2、333kg/cm2等三種強度混凝土分批進行載重試驗，探討不同配筋與強度下之剪力破壞情形及其配筋效應的表現，而由實驗結果發現，開裂前剪力主要仍由混凝土強度所控制，但開裂後的剪力行為則受到主筋插接效應的影響而有所差異，進一步分析顯示，拉力筋的補強效益較壓力筋為佳，而中性軸配筋的剪力摩擦效應對剪力的提升較其他配筋位置更為顯著，另在公式驗證上，ACI規範對剪力的預測較為保守，而Zustty公式雖較為精確，但兩者皆未考量中性軸配筋之影響。

關鍵字

主鋼筋 ； 剪力強度 ； 剪力破壞 ； 剪力行為

並列摘要

The internal codes of RC were still constituted by the source of ACI system.at present. This detection could be found when treat the destruct mode of RC. Failure mode of bending behavior have the tractility to be a warning for hold off. Whereas shear would often fracture in a second and make big toll. Accordingly, avoid the shear failure happening which had been an important subject of structural design. However, the causes of shear behavior are more complicated, and then the codes were underestimating the effect of main reinforcements for Vc and too conservative. So it is worth to amend more. Although the investigation of shear behavior has been some scale, it is still indefinite to compare with bending. Hence the related research should be proofed by more experiment.
　　In order to explore the effect of main reinforcements for shear behavior. This study produces thirty-six specimens of rectangular RC beams without stirrups, each specimen are 18cm×22cm×135cm. Using six types of the reinforced collocation and three strength of concrete with 170kg/cm2, 245kg/cm2, 333kg/cm2 to take the load experiment for find the conditions of shear failure with different reinforced types and the impact on expression. According to the experimental result, we can know the diagonal crack of shear strength be controlled by the tensile strength of concrete, but the behavior after crack is concerned to the connection of main reinforcements. Further to the analysis, the benefit of tensile reinforcements is better than compressive. And then the reinforcement of neutral axis have the influence of shear friction could improve definitely. Besides, the ACI codes is more conservative on demonstrating the formula and the formula of Zustty is more exact. Both don’t consider the effect of the neutral axis of reinforcement.

並列關鍵字

main reinforcements ； shear strength ； shear failure ； shear behavior

參考文獻

[12] 吳政諭（2008），「剪力筋對於鋼筋混凝土矩形梁剪力行為之影響」，國立台北科技大學土木與防災研究所碩士論文。

[19] 蕭乃為（2006），「無腹筋RC梁利用壓拉桿模式預測剪力強度之研究」，國立中央大學土木工程研究所碩士論文。

[16] 湯兆緯（2007），「無腹筋輕質粒料混凝土RC梁之剪力行為」，中國土木水利工程學刊，第19卷，第1期，第57-66頁。

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[3] Kani, G. N. J., “Basic facts concerning shear failure,” Journal of the ACI, June 1966, pp. 675-692.