裂缝深度及角度对混凝土断裂性能的影响

发布时间：2018-04-30 11:35

本文选题：混凝土 + 三点弯曲试验　；参考：《福建工程学院》2017年硕士论文

【摘要】：材料的断裂破坏一直是力学界研究的热点和难点,混凝土作为一种工程材料,在土木工程领域得到广泛的应用,将断裂力学的思想应用到研究混凝土断裂破坏,就形成了混凝土断裂力学。到目前,众多的学者对混凝土断裂破坏进行了大量的理论、试验和数值模拟的研究工作,取得了许多有价值的成果,为完善混凝土断裂力学也建立了一系列经典的断裂模型。然而,由于混凝土本身具有多相、非均匀等特点,混凝土断裂的力学行为和破坏机理还有许多工作需要进一步研究。为此,本文主要对含有裂缝的混凝土梁进行了以下几个方面的工作:(1)对15根混凝土梁进行了三点弯曲试验,试验参数为预制裂缝深度(40mm、60mm、80mm、100mm、120mm),采用位移加载的方式,研究混凝土梁在预制不同裂缝深度条件下断裂性能的变化。试验结果表明:随着预制裂缝深度的增大,混凝土试件起裂荷载Pini、最大荷载Pmax减小,断裂能Gf受其影响不明显;随着预制裂缝深度的增大,起裂断裂韧度K_(IC)~(ini)变化幅度较小,失稳断裂韧度K_(IC)~(un)有明显的减小趋势。(2)对18根V型切口混凝土梁进行了三点弯曲试验,试验参数为V型切口角度(15°、30°、45°、60°、75°、90°),采用位移加载的方式,研究混凝土梁在不同V型切口角度条件下断裂性能的变化。试验结果表明:随着V型切口角度的增大,混凝土试件起裂荷载Pini、最大荷载Pmax增大,断裂能Gf受其影响不明显;随着切口角度的增大,起裂断裂韧度K_(IC)~(ini)变化幅度较小,失稳断裂韧度K_(IC)~(un)有明显的增大趋势。(3)在试验基础上,利用通用有限元软件ABAQUS对两个系列的混凝土试件进行了有限元建模。模拟了混凝土梁三点弯曲试验的荷载-裂缝口张开位移(P-CMOD)全曲线,计算了各组试件的双K断裂韧度。结果表明:双K断裂韧度的试验值与有限元模拟值的偏差在10%以内,说明该有限元模型能够较好地模拟混凝土梁三点弯曲试验。(4)通过对不同切口角度θ的混凝土三点弯曲梁试件断裂韧度的分析,在原有裂缝深度对断裂韧度影响的经验公式基础上,得到了适用于V型切口混凝土梁失稳断裂韧度的计算公式。
[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 掳30 掳30 掳30 掳60 掳60 掳60 掳75 掳90 掳. 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.
【学位授予单位】：福建工程学院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528

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