本文選題：混凝土 + 三點(diǎn)彎曲試驗(yàn)��； 參考：《福建工程學(xué)院》2017年碩士論文

【摘要】：材料的斷裂破壞一直是力學(xué)界研究的熱點(diǎn)和難點(diǎn),混凝土作為一種工程材料,在土木工程領(lǐng)域得到廣泛的應(yīng)用,將斷裂力學(xué)的思想應(yīng)用到研究混凝土斷裂破壞,就形成了混凝土斷裂力學(xué)。到目前,眾多的學(xué)者對(duì)混凝土斷裂破壞進(jìn)行了大量的理論、試驗(yàn)和數(shù)值模擬的研究工作,取得了許多有價(jià)值的成果,為完善混凝土斷裂力學(xué)也建立了一系列經(jīng)典的斷裂模型。然而,由于混凝土本身具有多相、非均勻等特點(diǎn),混凝土斷裂的力學(xué)行為和破壞機(jī)理還有許多工作需要進(jìn)一步研究。為此,本文主要對(duì)含有裂縫的混凝土梁進(jìn)行了以下幾個(gè)方面的工作:(1)對(duì)15根混凝土梁進(jìn)行了三點(diǎn)彎曲試驗(yàn),試驗(yàn)參數(shù)為預(yù)制裂縫深度(40mm、60mm、80mm、100mm、120mm),采用位移加載的方式,研究混凝土梁在預(yù)制不同裂縫深度條件下斷裂性能的變化。試驗(yàn)結(jié)果表明:隨著預(yù)制裂縫深度的增大,混凝土試件起裂荷載Pini、最大荷載Pmax減小,斷裂能Gf受其影響不明顯;隨著預(yù)制裂縫深度的增大,起裂斷裂韌度K_(IC)~(ini)變化幅度較小,失穩(wěn)斷裂韌度K_(IC)~(un)有明顯的減小趨勢(shì)。(2)對(duì)18根V型切口混凝土梁進(jìn)行了三點(diǎn)彎曲試驗(yàn),試驗(yàn)參數(shù)為V型切口角度(15°、30°、45°、60°、75°、90°),采用位移加載的方式,研究混凝土梁在不同V型切口角度條件下斷裂性能的變化。試驗(yàn)結(jié)果表明:隨著V型切口角度的增大,混凝土試件起裂荷載Pini、最大荷載Pmax增大,斷裂能Gf受其影響不明顯;隨著切口角度的增大,起裂斷裂韌度K_(IC)~(ini)變化幅度較小,失穩(wěn)斷裂韌度K_(IC)~(un)有明顯的增大趨勢(shì)。(3)在試驗(yàn)基礎(chǔ)上,利用通用有限元軟件ABAQUS對(duì)兩個(gè)系列的混凝土試件進(jìn)行了有限元建模。模擬了混凝土梁三點(diǎn)彎曲試驗(yàn)的荷載-裂縫口張開(kāi)位移(P-CMOD)全曲線,計(jì)算了各組試件的雙K斷裂韌度。結(jié)果表明:雙K斷裂韌度的試驗(yàn)值與有限元模擬值的偏差在10%以內(nèi),說(shuō)明該有限元模型能夠較好地模擬混凝土梁三點(diǎn)彎曲試驗(yàn)。(4)通過(guò)對(duì)不同切口角度θ的混凝土三點(diǎn)彎曲梁試件斷裂韌度的分析,在原有裂縫深度對(duì)斷裂韌度影響的經(jīng)驗(yàn)公式基礎(chǔ)上,得到了適用于V型切口混凝土梁失穩(wěn)斷裂韌度的計(jì)算公式。
[Abstract]:Fracture failure of materials has always been a hot and difficult point in the field of mechanics. As a kind of engineering material, concrete has been widely used in the field of civil engineering, and the idea of fracture mechanics has been applied to the study of fracture failure of concrete. The fracture mechanics of concrete is formed. Up to now, many scholars have done a lot of theoretical, experimental and numerical simulation work on the fracture failure of concrete. Many valuable results have been obtained, and a series of classical fracture models have been established to perfect the fracture mechanics of concrete. However, because the concrete itself has the characteristics of multiphase and non-uniformity, the mechanical behavior and failure mechanism of concrete fracture need to be further studied. Therefore, in this paper, the concrete beams with cracks are mainly studied in the following aspects: 1) the three-point bending tests of 15 concrete beams are carried out. The experimental parameters are prefabricated crack depth of 40mm / 60mm / 80mm / 100mm / 100mm / 120mm, and displacement loading method is adopted. The change of fracture behavior of concrete beams under different crack depth was studied. The experimental results show that with the increase of precast crack depth, the initial crack load of concrete specimen is pini, the maximum load Pmax decreases, and the fracture energy G f is not affected by the prefabricated crack depth. There is an obvious decreasing trend of unstable fracture toughness (K _ S). (2) Three-point bending tests on 18 V-notched concrete beams have been carried out. The experimental parameters are as follows: V-shaped notch angle 15 擄30 擄30 擄30 擄60 擄60 擄60 擄75 擄90 擄. Displacement loading method is used. The fracture behavior of concrete beams at different V-notch angles was studied. The experimental results show that with the increase of V-notch angle, the initial crack load of concrete specimens increases, the maximum load Pmax increases, and the fracture energy G _ f is not affected obviously, but with the increase of the notch angle, the crack toughness K _ T _ I _ (I) of concrete specimen changes slightly, and the fracture energy G _ (f) of concrete specimen increases with the increase of the notch angle. On the basis of experiments, two series of concrete specimens are modeled by finite element method (ABAQUS). The load-crack opening displacement (P-CMOD) curve of three-point bending test of concrete beams is simulated and the double-K fracture toughness of each group of specimens is calculated. The results show that the deviation between the test value of double K fracture toughness and the finite element simulation value is less than 10%. It shows that the finite element model can well simulate the three-point bending test of concrete beams. The fracture toughness of concrete three-point bending beams with different notch angles 胃 is analyzed. Based on the empirical formula of the influence of fracture depth on fracture toughness, a formula for calculating the instability fracture toughness of V-notch concrete beam is obtained.
【學(xué)位授予單位】：福建工程學(xué)院
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TU528

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