發(fā)布時間：2018-04-27 13:14

  本文選題：混凝土 + 動力沖擊性能�。� 參考：《清華大學(xué)》2015年博士論文

【摘要】：混凝土在動力荷載作用下,其本構(gòu)關(guān)系與破壞性能顯示出明顯的與加載速率相關(guān)的特征,同時動力強度隨應(yīng)變率的增加而增加,即率相關(guān)效應(yīng)。本文基于細觀顆粒元數(shù)值模型和動力試驗相結(jié)合的方法,對混凝土沖擊性能進行分析和研究。論文的主要研究工作和創(chuàng)新成果有:1.基于細觀顆粒元模型,對混凝土直拉、劈拉、彎拉強度試驗進行仿真,數(shù)值和試驗中靜動力抗拉強度結(jié)果符合良好,三種抗拉強度關(guān)系符合現(xiàn)行統(tǒng)計經(jīng)驗公式,驗證了仿真模型的有效性。2.建立穩(wěn)定可靠的混凝土落錘沖擊試驗測試系統(tǒng),通過改變重錘質(zhì)量、下落高度和錘頭材料完成了不同加載速率的沖擊試驗,對試驗中混凝土梁的承載力、動態(tài)位移、應(yīng)變、斷裂過程、動量-沖量平衡關(guān)系、慣性力和斷裂能等動力特性進行了測量和分析。3.基于細觀顆粒元建立落錘-結(jié)構(gòu)全系統(tǒng)仿真模型,對沖擊試驗進行全過程模擬,研究了系統(tǒng)能量轉(zhuǎn)化過程,并提出顆粒元能量模式與傳統(tǒng)斷裂能的轉(zhuǎn)換關(guān)系。細觀數(shù)值方法與試驗的相互驗證揭示了混凝土動力沖擊性能與破壞機理。4.設(shè)計了無粘結(jié)預(yù)應(yīng)力混凝土梁沖擊試驗,對鋼筋屈服-混凝土斷裂的非線性相互作用過程進行系統(tǒng)分析,證明預(yù)應(yīng)力鋼筋限制了混凝土的變形和裂紋擴展,鋼筋的屈服程度決定了混凝土的裂紋擴展和多次沖擊的剩余承載力。5.基于顆粒元-有限差耦合方法,建立無粘結(jié)預(yù)應(yīng)力混凝土梁沖擊試驗仿真模型,其中混凝土顆粒單元和鋼筋桿單元在錨固點交互作用,對混凝土損傷斷裂和鋼筋屈服進行模擬,并與試驗結(jié)果進行了比較研究。表明顆粒元-有限差耦合模型適用于鋼筋-混凝土類復(fù)合材料的動力特性與破壞機理研究。6.基于顆粒元模型對混凝土進行動力彎曲模擬,解釋了初始靜載影響的力學(xué)機理。對力鏈、裂紋發(fā)展和能量過程進行分析,揭示當(dāng)初始靜載水平處于靜力線彈性階段時,動力強度隨初始靜載增加,初始靜載處于靜力線彈性極限時,動力強度最大;而當(dāng)初始靜載處于靜力的損傷軟化階段時,初始裂紋的產(chǎn)生使結(jié)構(gòu)產(chǎn)生損傷,動力強度下降。
[Abstract]:Under dynamic load, the constitutive relation and destructive energy of concrete show obvious characteristics related to loading rate, and the dynamic strength increases with the increase of strain rate, that is, rate-dependent effect. Based on the mesoscopic particle element numerical model and dynamic test, the impact performance of concrete is analyzed and studied in this paper. The main research work and innovative achievements of the thesis are: 1. 1. Based on the mesoscopic particle element model, the tests of Czochralski, split and bending tensile strength of concrete are simulated. The numerical results agree well with the results of static and dynamic tensile strength in the tests, and the three kinds of tensile strength relations accord with the current statistical empirical formulas. The validity of the simulation model is verified. 2. A stable and reliable impact test system for concrete drop hammer is established. By changing the weight of the hammer, the falling height and the material of the hammer head, the impact tests with different loading rates are completed, and the bearing capacity, dynamic displacement and strain of the concrete beam are tested. The dynamic characteristics of fracture process, momentum impulse balance, inertial force and fracture energy are measured and analyzed. Based on the mesoscopic particle element, the full-system simulation model of drop weight and structure was established, and the whole process of impact test was simulated. The energy transformation process of the system was studied, and the relationship between the energy model of particle element and the traditional fracture energy was put forward. The mutual verification of mesoscopic numerical method and test reveals the dynamic impact performance and failure mechanism of concrete. 4. The impact test of unbonded prestressed concrete beam is designed, and the nonlinear interaction process of yield concrete fracture is analyzed systematically. It is proved that the prestressed steel bar restricts the deformation and crack propagation of concrete. The yield degree of steel bars determines the crack growth of concrete and the residual bearing capacity of multiple impact. Based on the coupling method of particle element and finite difference, a simulation model of impact test of unbonded prestressed concrete beam is established, in which the concrete particle element and the reinforced bar element interact at the anchoring point to simulate the damage and fracture of concrete and the yield of steel bar. The results are compared with the experimental results. The results show that the particle element finite difference coupling model is suitable for the study of dynamic characteristics and failure mechanism of reinforced concrete composites. Based on the particle element model, the dynamic bending of concrete is simulated, and the mechanical mechanism of initial static load is explained. The analysis of force chain, crack development and energy process shows that when the initial static load level is in the static linear elastic stage, the dynamic strength increases with the initial static load, and the initial static load is at the static linear elastic limit, the dynamic strength is the largest. When the initial static load is in the stage of static damage softening, the initial crack causes damage and the dynamic strength decreases.
【學(xué)位授予單位】：清華大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TU528

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本文編號：1810873