混凝土受压与受拉性能的尺寸效应研究

发布时间：2018-02-25 19:28

本文关键词： 混凝土配筋混凝土尺寸效应抗压强度弯拉强度数值分析　出处：《湖南大学》2013年博士论文　论文类型：学位论文

【摘要】：混凝土的力学性能与其几何尺寸密切相关，为准确描述不同混凝土力学性能上的差异，系统研究混凝土的尺寸效应显得尤为必要。目前，国内外在混凝土受压变形性能尺寸效应、骨料组分和配筋情况对混凝土力学性能尺寸效应的影响等方面的研究较少。此外，在对混凝土力学性能进行数值模拟时，，通常将硬化水泥砂浆基体的力学性能假定为一常数进行分析，忽略其自身的尺寸效应，该假定的有效性尚未得到试验证实。受各种因素的限制，尺寸效应的试验研究往往只能在一个较小的尺度范围内进行，采用数值模拟的方法可有效解决试验研究的不足之处，为尺寸效应的研究提供另外一种研究手段。采用试验研究与数值分析相结合的方法，对混凝土的受压与弯拉性能尺寸效应进行了较系统研究。主要研究内容如下： 1.对162个立方体试件的抗压强度尺寸效应进行了试验研究，结果表明：混凝土抗压强度具有尺寸效应，边长150mm和200mm试件的抗压强度约为边长100mm试件的94%和88%；混凝土、砂浆和净浆抗压强度的尺寸效应依次减弱，砂浆与净浆的尺寸效应仅为混凝土的1/3和30%左右；混凝土抗压强度的尺寸效应随着强度等级的提高而增强，C60混凝土的尺寸效应约为C20混凝土的1.8倍。 2.对216个棱柱体试件单轴受压性能尺寸效应进行了试验研究，结果表明：混凝土单轴受压性能具有较明显的尺寸效应，边长200mm试件的峰值应力、应变及极限应变分别为100mm试件的85%、104%和110%。边长150mm试件的峰值应力、应变及极限应变分别为100mm试件的92%、102%与105%；强度等级越高，尺寸效应越明显，C20混凝土的尺寸效应仅为C60混凝土的1/2；尺寸效应受骨料组分影响较大，混凝土的尺寸效应分别约为砂浆和净浆的2.7倍和2.8倍；配筋混凝土的尺寸效应明显弱于混凝土试件，对于配筋率约1%时的钢筋混凝土，其内混凝土的尺寸效应约为未配筋混凝土的28%左右。 3.对162个棱柱体试件弯拉性能试验研究结果表明：弯拉强度具有尺寸效应，边长70mm和100mm混凝土试件的弯拉强度分别为150mm试件的1.15倍和1.1倍；混凝土弯拉强度的尺寸效应强于砂浆和净浆，砂浆和净浆的尺寸效应分别为混凝土的30%和24%；强度等级对弯拉强度尺寸效应影响较大，C60混凝土弯拉强度的尺寸效应约为C20混凝土的2倍。 4.对统计尺寸效应理论、基于能量释放准则的尺寸效应理论及基于裂纹分形特征的尺寸效应理论进行了比较分析，基于试验数据，给出了各尺寸效应率中相关参数的建议值，提出了不同强度等级混凝土立方体抗压强度、轴心抗压强度以及弯拉强度尺寸效应率中各参数的计算公式。定义临界尺寸和临界强度为：当试件几何尺寸大于某一尺寸后，抗压和抗拉强度的变化率分别小于0.01和0.001，则该尺寸为临界尺寸，相应的强度为临界强度。混凝土各力学性能参数的临界尺寸均随强度等级的提高而增大，C40和C60混凝土的临界尺寸分别约为C20混凝土的1.7倍和2.1倍。 5.编写了随机骨料的投放程序，建立了二维与三维混凝土随机骨料模型。基于试验数据和随机骨料模型，得到了各强度等级混凝土中粘结界面层的力学性能参数，建立了粘结界面层力学性能与混凝土宏观力学性能间的关系。 6.采用均质弹脆性、非均质弹脆性和均质弹塑性模型对混凝土的单轴受压性能进行了数值模拟，得到了破坏过程和宏观应力-应变全曲线，结果表明：非均质弹脆性模型得到的上升段和均质弹塑性模型得到的全曲线与试验结果吻合较好。 7.采用随机骨料模型分析了混凝土的受压和受拉性能，研究了各力学性能参数的尺寸效应，提出了相应的尺寸效应率，得到了临界尺寸和临界强度。结果表明：临界尺寸随强度等级的提高而增大，C40与C60混凝土的临界尺寸分别约为C20混凝土的1.8倍和2.4倍；配筋混凝土中混凝土强度的临界尺寸明显低于未配筋混凝土，临界强度高于未配筋混凝土，当配筋率为1%时，其临界尺寸和临界强度分别为未配筋混凝土的45%和1.3倍左右。
[Abstract]:The mechanical properties of concrete are closely related to their geometric dimensions . In order to accurately describe the differences in mechanical properties of concrete , it is necessary to study the size effect of concrete . With the combination of experimental research and numerical analysis , a systematic study is carried out on the effect of compression and bending performance dimension of concrete . The main research contents are as follows : 1 . The compressive strength dimension effect of 162 cube specimens is studied . The results show that the compressive strength of concrete , side length 150mm and 200mm is about 94 % and 88 % of the side length 100mm test piece . The dimension effect of concrete , mortar and net pulp is about 1 / 3 and 30 % of concrete . The dimension effect of concrete compressive strength is enhanced with the increase of strength grade , and the dimension effect of C60 concrete is about 1.8 times of C20 concrete . 2 . The size effect of single - axis compressive property of 216 prism specimens is studied . The results show that the compressive property of concrete uniaxial compression has obvious dimension effect , and the peak stress , strain and ultimate strain of 200 mm specimens are respectively 85 % , 104 % and 110 % of 100 mm specimens respectively . The higher the strength grade , the more obvious the size effect is , the dimension effect of C20 concrete is about 2.7 times and 2.8 times of that of C60 concrete respectively . The dimension effect of reinforced concrete is about 2 . 7 times and 2.8 times of mortar and net pulp , respectively . The dimension effect of reinforced concrete is about 28 % of unreinforced concrete . 3 . The tensile strength of 162 prism specimens is tested . The results show that the bending strength of concrete specimens is 1.15 times and 1.1 times that of 150mm specimens respectively . The dimension effect of concrete bending strength is greater than 30 % and 24 % of the concrete , and the strength grade has great influence on bending strength dimension effect , and the size effect of the flexural strength of C60 concrete is about 2 times of C20 concrete . 4 . According to the theory of statistical dimension effect , based on the theory of dimension effect of energy release criterion and the theory of dimension effect based on the fractal characteristics of crack , the calculation formulas of the parameters in each dimension effect rate are given . The critical dimension and the critical strength are as follows : when the geometric dimension of the test piece is bigger than a certain size , the change rate of compressive strength and tensile strength is less than 0.01 and 0.001 respectively . The critical dimension of each mechanical property parameter of concrete is increased with the increase of strength grade , and the critical dimension of C40 and C60 concrete is about 1.7 times and 2.1 times of C20 concrete respectively . Based on the experimental data and the random aggregate model , the mechanical property parameters of the bonding interface layer in each strength grade concrete are obtained , and the relationship between the mechanical properties of the bonded interface layer and the macroscopic mechanical properties of the concrete is established . 6 . The uniaxial compressive properties of concrete are numerically simulated by homogeneous elastic brittle , non - homogeneous elastic brittle and homogeneous elastic - plastic model . The failure process and the macroscopic stress - strain curve are obtained . The results show that the whole curve obtained by the non - homogeneous elastic brittle model is in good agreement with the experimental results . 7 . The compressive and tensile properties of concrete are analyzed by using random aggregate model . The dimension effect of each mechanical property parameter is studied . The critical dimension and critical strength are obtained . The critical dimension of C40 and C60 concrete is about 1.8 times and 2.4 times of C20 concrete respectively . The critical dimension of concrete in reinforced concrete is obviously lower than that of unreinforced concrete . When the reinforcement ratio is 1 % , the critical dimension and critical strength are about 45 % and 1.3 times of unreinforced concrete respectively .

【学位授予单位】：湖南大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TU528

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