部分預力普通強度混凝土Ｉ形梁之剪力強度研究

Study on the Shear Strength of Partially Prestressed Normal Strength Concrete I Beams

陳憲宏(Hsien-Hung Chen)

指導教授 ： 黃世建

共同指導教授 ： 徐增全(Thomas T. C. Hsu)

國立臺灣大學/工學院/土木工程學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.02790

摘要

一般相信RC梁中混凝土抗剪強度之貢獻，其係源自粗骨材之粒料互鎖效應、壓力區混凝土之參與、以及軸向鋼筋之插筋效應。若是粗骨材之粒料互鎖為主要之強度來源，則其設計公式宜以梁之有效深度（d）為計算參數。若是壓力區混凝土之參與為強度之主控，則其設計公式宜以梁之壓力區（c）為計算參數。現行規範採用粒料互鎖之設計概念，但已有研究顯示或許混凝土壓力區之大小才是主控之參數。
　　為釐清此一疑問，此研究共規劃8座Ｉ形梁試體以及8座矩形梁試體，採用了30 MPa以及80 MPa兩種混凝土強度，分別變化其加載之預力量，對其進行剪力試驗，實驗測試至梁兩端都破壞，一座梁試體可得到兩組載重位移曲線，透過實驗結果，可了解預力的加載對於混凝土梁之剪力強度之影響，並可鑑定梁之壓力區深度是否為混凝土抗剪強度之主要參數，此外亦比較ACI規範、AASHTO規範以及UH剪力強度公式之預測結果。
　　本論文單就整體系列試驗中，混凝土強度為30 MPa的Ｉ形梁探討之，試驗結果顯示，預力之加載確實能夠提升Ｉ形梁的剪力強度，同時預力將會降低其位移能力，破壞模式會較趨脆性。但混凝土抗剪強度的主要貢獻是否來自於壓力區之混凝土，仍需後續實驗的完成與比較來佐證。

關鍵字

預力混凝土梁 ； 混凝土抗剪強度貢獻 ； 剪力強度 ； 部分預力

並列摘要

It is generally believed that the shear strength contributed by concrete consists of aggregate interlocking, compressive concrete and dowel action. If the major contribution comes from aggregate interlocking, the design parameter of Vc should adopt the effective depth (d) of beam. However, if the concrete contribution is dominated by compressive concrete, the design parameter of Vc should select the depth of compression zone (c). The current code employs the design concept of aggregate interlocking. But some researchers found that the size of compression zone of beam might govern the concrete contribution of shear strength.
To solve this dilemma, we schemed a test series which includes 8 I-shaped beams and 8 rectangular beams with concrete strength of 30 MPa and 80 MPa. We applied different amount of prestress load on each specimen and tested on both ends of each specimen up to failure. After the tests, we can get two force-deflection curves from each specimen. By varying the size of compression zone of beam due to prestressing, we can examine the effect of prestress load on shear strength and the role of beam compression zone for shear contribution.
In this thesis, we only focus on four I-shaped beams with concrete strength 30 MPa. From test results, prestress load can obviously increase the shear strength of I beams, so the compression zone seems to dominate the concrete contribution of shear strength. In the other end, prestress load also lowers the deflection capability of I beams, leading to brittle failure mode. However, we can not conclude exactly if the shear strength mainly comes from the compression zone at this step. We need to finish the rest of experiments in the test series and study all the results, then come up with a firm conclusion.

並列關鍵字

Concrete Contribution ； Partially Prestressed ； Prestressed Beam ； Shear Strength

參考文獻

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