【摘要】：混凝土作為一種典型的多相非均質(zhì)復(fù)合材料,在土木工程領(lǐng)域有著非常廣泛的應(yīng)用,其材料性能與混凝土結(jié)構(gòu)的耐久性和安全性等有著密切的聯(lián)系�；炷羶�(nèi)部各相材料的力學(xué)性能差距很大,加之微裂紋、孔隙和其它初始缺陷的存在導(dǎo)致混凝土的基本性能變化規(guī)律有待進(jìn)一步研究。數(shù)值分析方法作為研究混凝土劣化機(jī)理的重要手段,可以在各項(xiàng)試驗(yàn)數(shù)據(jù)和理論研究的支持下對(duì)混凝土的各項(xiàng)力學(xué)性能進(jìn)行模擬和預(yù)測(cè),是當(dāng)下混凝土材料性能研究的熱點(diǎn)之一�；炷猎诩�(xì)觀層次上可以看作是由粗細(xì)骨料、水泥漿體和各種初始缺陷點(diǎn)等組成的復(fù)合材料�；诩�(xì)觀分析方法的混凝土數(shù)值模型,在參數(shù)選擇合理的情況下不僅可以直觀的反映出混凝土各相組成對(duì)其性能的影響以及持續(xù)變化荷載作用下的整個(gè)損傷斷裂過(guò)程,而且可以避免實(shí)體試驗(yàn)中環(huán)境因素和人為失誤等客觀原因?qū)υ囼?yàn)結(jié)果的影響。本文基于混凝土細(xì)觀隨機(jī)骨料模型,將損傷力學(xué)理論應(yīng)用到數(shù)值分析中,模擬研究了混凝土試件在單軸荷載作用下的的損傷破壞過(guò)程,并在數(shù)值模型的建立過(guò)程中引入等效化方法的概念,通過(guò)等效前后模擬結(jié)果的對(duì)比驗(yàn)證了等效化方法在混凝土的細(xì)觀損傷模型中應(yīng)用的合理性。具體工作如下:1.闡述了等效化方法及混凝土損傷斷裂力學(xué)的基本概念,并研究了等效化方法在混凝土細(xì)觀力學(xué)分析中的具體應(yīng)用。2.在數(shù)值軟件中運(yùn)用蒙特卡洛方法,通過(guò)編寫程序化語(yǔ)言實(shí)現(xiàn)了圓形骨料顆粒在指定的區(qū)域和骨料級(jí)配范圍內(nèi)的隨機(jī)分布。然后對(duì)生成的骨料坐標(biāo)數(shù)據(jù)進(jìn)行處理,添加界面單元最終生成二維混凝土試件的幾何模型。3.對(duì)有限元軟件進(jìn)行二次開(kāi)發(fā),將雙折線損傷模型引入到混凝土試件的單軸受拉、單軸受壓的數(shù)值模擬中去,通過(guò)設(shè)置狀態(tài)變量判斷單元是否失效刪除,進(jìn)而模擬出混凝土內(nèi)部裂紋的擴(kuò)展規(guī)律,并得到相應(yīng)的應(yīng)力應(yīng)變曲線。4.將等效化方法應(yīng)用到數(shù)值模型中去,即把砂漿基質(zhì)與界面過(guò)渡區(qū)等效為一種材料,通過(guò)與原三相材料模型的試驗(yàn)結(jié)果進(jìn)行對(duì)比,驗(yàn)證方法的可靠性,并在子程序中創(chuàng)建損傷變量輸出模塊,較為直觀地反映等效后模型的損傷斷裂過(guò)程。5.討論了混凝土的界面厚度、骨料粒徑選取范圍和孔隙率對(duì)其性能的影響。本文運(yùn)用等效化方法簡(jiǎn)化了模型的建立過(guò)程,而且開(kāi)發(fā)出了模型的損傷變量輸出模塊,在提高模型計(jì)算效率的同時(shí)可以更真實(shí)和直觀地表達(dá)混凝土在單軸荷載作用下的損傷斷裂過(guò)程。為進(jìn)行混凝土基本性能的細(xì)觀分析提供技術(shù)支持,為對(duì)混凝土結(jié)構(gòu)進(jìn)行結(jié)構(gòu)分析與優(yōu)化設(shè)計(jì)奠定理論基礎(chǔ)。
[Abstract]:As a typical heterogeneous composite material, concrete has been widely used in civil engineering. Its properties are closely related to the durability and safety of concrete structures. The difference of mechanical properties between different phases of concrete is very large, and the existence of micro-cracks, pores and other initial defects lead to the further study of the basic performance of concrete. As an important means to study the deterioration mechanism of concrete, numerical analysis method can be used to simulate and predict the mechanical properties of concrete under the support of experimental data and theoretical research. At present, it is one of the hot spots in the research of concrete material performance. At the meso level, concrete can be regarded as a composite composed of coarse aggregate, cement paste and various initial defect points. The numerical model of concrete based on the mesoscopic analysis method can not only reflect the effect of each phase composition of concrete on its performance but also the whole damage and fracture process of concrete under the action of continuous changing load under reasonable selection of parameters. Moreover, it can avoid the influence of environmental factors and human error on the test results. Based on the concrete meso-random aggregate model, the damage mechanics theory is applied to the numerical analysis, and the damage and failure process of concrete specimen under uniaxial load is simulated. The concept of equivalent method is introduced in the process of establishing the numerical model. The rationality of the application of the equivalent method in the meso-damage model of concrete is verified by the comparison of the results of the simulation before and after the equivalence. The work is as follows: 1. This paper expounds the basic concept of equivalent method and concrete damage fracture mechanics, and studies the concrete application of equivalent method in concrete meso-mechanics analysis. The Monte Carlo method is used in the numerical software to realize the random distribution of the circular aggregate particles in the specified area and the aggregate gradation range by programming language. Then, the data of aggregate coordinate are processed, and the geometric model of two-dimensional concrete specimen is generated by adding interface element. The double broken line damage model is introduced into the numerical simulation of uniaxial tension and uniaxial compression of concrete specimens, and the state variables are set to determine whether the unit is invalid or not. Furthermore, the propagation law of internal crack in concrete is simulated, and the corresponding stress-strain curve. 4. The equivalent method is applied to the numerical model, that is, the mortar matrix is equivalent to the interfacial transition zone as a kind of material, and the reliability of the method is verified by comparing the experimental results with the original three-phase material model. The damage variable output module is created in the subprogram to reflect the damage fracture process of the equivalent model. The influence of interfacial thickness of concrete, selection range of aggregate particle size and porosity on its performance is discussed. In this paper, the process of establishing the model is simplified by using the method of equivalence, and the output module of the damage variable of the model is developed. The damage and fracture process of concrete under uniaxial load can be expressed more realistically and intuitively while improving the efficiency of model calculation. It provides technical support for the mesoscopic analysis of the basic properties of concrete and lays a theoretical foundation for structural analysis and optimum design of concrete structures.
【學(xué)位授予單位】：河南工業(yè)大學(xué)
【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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