本文選題：混凝土　切入點：細(xì)觀力學(xué)　出處：《西北農(nóng)林科技大學(xué)》2015年碩士論文

【摘要】：混凝土結(jié)構(gòu)經(jīng)常處于水環(huán)境中,水就會滲入到混凝土的微裂紋和孔隙中,使混凝土材料的靜動力學(xué)性能發(fā)生一系列的改變,對混凝土結(jié)構(gòu)的強度和耐久性產(chǎn)生一定影響。在水環(huán)境工作的混凝土建筑物不可避免地會承受地震荷載、波浪荷載、沖擊荷載甚至爆炸荷載等動力荷載,混凝土在動態(tài)荷載下的力學(xué)特性有別于其在靜荷載下的力學(xué)性能。因此為保證在水環(huán)境工作的混凝土建筑物的安全運行,就有必要開展水環(huán)境影響下的混凝土強度、彈性模量等力學(xué)性能的變化規(guī)律和破壞機理的研究�；诤暧^唯象學(xué)的研究模型并不能揭示混凝土材料復(fù)雜的細(xì)觀特征和力學(xué)性能的變化機理,因此本文基于細(xì)觀力學(xué)方法,以不同含水量混凝土在靜動力荷載下的力學(xué)性能為主要研究對象,分析了C20和C30兩種強度等級混凝土的抗壓強度隨含水量及加載速率的變化規(guī)律和破壞機理,所做工作及取得的成果如下:(1)從混凝土材料的細(xì)觀結(jié)構(gòu)出發(fā),將混凝土視為由骨料、砂漿和兩者之間的粘結(jié)界面組成的三相復(fù)合材料,基于蒙特卡羅方法和瓦拉文公式,生成了與真實混凝土結(jié)構(gòu)相似的二維隨機骨料模型。以ANSYS/LS-DYNA有限元分析軟件為平臺,引入彈脆性細(xì)觀損傷本構(gòu)對混凝土試樣單軸壓縮斷裂過程進行了數(shù)值模擬,分析了混凝土的破壞機理。(2)在隨機骨料三相復(fù)合材料模型的基礎(chǔ)上,通過隨機改變單元的材料屬性的方法生成了6種不同含水量的混凝土細(xì)觀數(shù)值模型,對不同含水量混凝土的單軸壓縮破壞過程進行了數(shù)值模擬,研究了水分對混凝土靜力力學(xué)性能的影響規(guī)律。通過將數(shù)值模型計算結(jié)果和夾雜理論結(jié)果比較,驗證了本文所建模型的合理性和計算結(jié)果的可靠性。研究表明:混凝土的靜抗壓強度隨含水量的增加而降低,初始彈性模量隨含水量的增加有所提高。(3)設(shè)計了不同含水量混凝土的動態(tài)加載數(shù)值試驗方案,綜合分析了強度等級、含水量及加載速率三種因素對混凝土抗壓強度的影響規(guī)律。研究表明:含水量是影響混凝土動態(tài)抗壓強度的一個重要因素,高含水量混凝土的率敏感性比干燥和低含水量混凝土更為顯著;高強度等級混凝土的率效應(yīng)比低強度等級混凝土的率效應(yīng)小。
[Abstract]:The concrete structure is often in the water environment, the water will seep into the microcracks and pores of the concrete, and make a series of changes in the static and dynamic behavior of the concrete material. Concrete buildings working in water environment will inevitably bear dynamic loads such as earthquake load, wave load, impact load and even explosion load. The mechanical properties of concrete under dynamic load are different from those under static load. Therefore, in order to ensure the safe operation of concrete buildings working in water environment, it is necessary to carry out concrete strength under the influence of water environment. The research model based on macrophenomenology can not reveal the complex meso-characteristics and the mechanism of mechanical properties of concrete, so this paper bases on the method of meso-mechanics. Taking the mechanical properties of concrete with different moisture content under static and dynamic loads as the main research object, the variation law and failure mechanism of compressive strength with water content and loading rate of concrete of two strength grades C20 and C30 are analyzed. The work done and the results obtained are as follows: 1) starting from the mesoscopic structure of concrete materials, the concrete is regarded as a three-phase composite composed of aggregate, mortar and the bond interface between them, based on Monte Carlo method and Varavan formula. A two-dimensional random aggregate model, which is similar to the real concrete structure, is generated. Based on the ANSYS/LS-DYNA finite element analysis software, the elastic brittle meso-damage constitutive model is introduced to simulate the uniaxial compressive fracture process of concrete samples. The failure mechanism of concrete is analyzed. (2) based on the three-phase composite material model of random aggregate, six kinds of meso-numerical models of concrete with different moisture content are generated by randomly changing the material properties of the element. In this paper, the uniaxial compression failure process of concrete with different moisture content is numerically simulated, and the influence of moisture on the static mechanical properties of concrete is studied. The numerical model results are compared with the inclusion theory results. The rationality of the model and the reliability of the calculation results are verified. The results show that the static compressive strength of concrete decreases with the increase of water content. The initial modulus of elasticity increases with the increase of water content. The dynamic loading numerical test scheme of concrete with different water content is designed, and the strength grade is analyzed synthetically. The effects of water content and loading rate on the compressive strength of concrete are studied. The results show that water content is an important factor affecting the dynamic compressive strength of concrete. The rate sensitivity of high water content concrete is more obvious than that of dry concrete and low water content concrete, and the rate effect of high strength grade concrete is less than that of low strength grade concrete.
【學(xué)位授予單位】：西北農(nóng)林科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TU528

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本文編號：1672638