【摘要】：該文使用數(shù)字圖像相關(guān)方法實(shí)時(shí)觀(guān)測(cè)三點(diǎn)彎試驗(yàn)中切口混凝土梁全場(chǎng)變形,分析混凝土梁斷裂破壞過(guò)程中水平位移和應(yīng)變的變化規(guī)律,基于切口處水平位移和應(yīng)變變化規(guī)律確定起裂荷載,并研究?jī)鋈谘h(huán)次數(shù)和纖維摻量對(duì)混凝土起裂韌度、失穩(wěn)韌度、臨界開(kāi)口位移的影響,結(jié)果表明:對(duì)于C30混凝土而言,起裂韌度和失穩(wěn)韌度隨凍融次數(shù)的增加而減小,降幅約為0.6 MPa·m~(1/2)~0.80 MPa·m~(1/2),兩種韌度隨玄武巖纖維摻量增加有小幅增加,最大增幅分別約為0.1 MPa·m~(1/2)和0.2 MPa·m~(1/2),說(shuō)明玄武巖纖維能提高C30混凝土的抗凍性,但提高程度是一定的,玄武巖纖維不能完全抑制凍融對(duì)混凝土的損傷;纖維摻量對(duì)失穩(wěn)韌度的提高幅度要比起裂韌度大;起裂韌度增益比和失穩(wěn)韌度增益比都隨纖維摻量增加先增大后減小,兩種韌度增益比均在纖維摻量為2.0 kg/m~3時(shí)最大,因此,在混凝土強(qiáng)度等級(jí)為C30時(shí),2.0 kg/m~3可作為最佳纖維摻量;臨界開(kāi)口位移隨凍融次數(shù)增加而增大,隨纖維摻量變化效果不明顯,與纖維增強(qiáng)作用相比凍融損傷是影響斷裂過(guò)程變形性能的主要因素;最后在試驗(yàn)結(jié)果的基礎(chǔ)上,建立了起裂韌度和失穩(wěn)韌度隨纖維摻量和凍融次數(shù)的擬合模型。
[Abstract]:In this paper, digital image correlation method is used to observe the full-field deformation of notch concrete beam in three-point bending test in real time, and the variation law of horizontal displacement and strain during fracture and failure of concrete beam is analyzed. Based on the horizontal displacement and strain variation at the notch, the crack initiation load is determined, and the effects of freeze-thaw cycle times and fiber content on the crack initiation toughness, instability toughness and critical opening displacement of concrete are studied. The results show that: for C30 concrete, the crack initiation toughness, instability toughness and critical opening displacement are affected by the number of freeze-thaw cycles. The initial fracture toughness and instability toughness decreased with the increase of freezing and thawing times, about 0.6 MPa m2 ~ 0.80 MPa m ~ (1 / 2), and the two types of toughness increased slightly with the increase of basalt fiber content. The maximum increases are about 0.1 MPa m2 and 0.2 MPa m2, respectively, indicating that basalt fiber can improve the frost resistance of C30 concrete, but the degree of improvement is certain, basalt fiber can not completely inhibit the damage to concrete caused by freeze-thaw. The increase of the initial toughness gain ratio and the instability toughness gain ratio increased firstly and then decreased with the increase of fiber content, and the maximum toughness gain ratio of the two fibers was 2. 0 kg/m~ 3, so the ratio of initial toughness gain and instability toughness gain ratio increased with the increase of fiber content, and the ratio of initial toughness gain ratio and instability toughness gain ratio increased firstly and then decreased with the increase of fiber content. When the strength grade of concrete is C30, 2.0 kg/m~3 can be regarded as the best fiber content, and the critical opening displacement increases with the increase of freeze-thaw times, but the effect is not obvious with the fiber content. Freezing and thawing damage is the main factor affecting the deformation property of fracture process compared with fiber reinforcement. Finally, a fitting model of initial crack toughness and instability toughness with fiber content and freeze-thaw number is established on the basis of experimental results.
【作者單位】： 內(nèi)蒙古工業(yè)大學(xué)土木工程學(xué)院;
【基金】：國(guó)家自然科學(xué)基金項(xiàng)目(11362013)
【分類(lèi)號(hào)】：TU528

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