混凝土动力冲击性能试验与细观数值仿真研究

发布时间：2018-04-27 13:14

本文选题：混凝土 + 动力冲击性能　；参考：《清华大学》2015年博士论文

【摘要】：混凝土在动力荷载作用下,其本构关系与破坏性能显示出明显的与加载速率相关的特征,同时动力强度随应变率的增加而增加,即率相关效应。本文基于细观颗粒元数值模型和动力试验相结合的方法,对混凝土冲击性能进行分析和研究。论文的主要研究工作和创新成果有:1.基于细观颗粒元模型,对混凝土直拉、劈拉、弯拉强度试验进行仿真,数值和试验中静动力抗拉强度结果符合良好,三种抗拉强度关系符合现行统计经验公式,验证了仿真模型的有效性。2.建立稳定可靠的混凝土落锤冲击试验测试系统,通过改变重锤质量、下落高度和锤头材料完成了不同加载速率的冲击试验,对试验中混凝土梁的承载力、动态位移、应变、断裂过程、动量-冲量平衡关系、惯性力和断裂能等动力特性进行了测量和分析。3.基于细观颗粒元建立落锤-结构全系统仿真模型,对冲击试验进行全过程模拟,研究了系统能量转化过程,并提出颗粒元能量模式与传统断裂能的转换关系。细观数值方法与试验的相互验证揭示了混凝土动力冲击性能与破坏机理。4.设计了无粘结预应力混凝土梁冲击试验,对钢筋屈服-混凝土断裂的非线性相互作用过程进行系统分析,证明预应力钢筋限制了混凝土的变形和裂纹扩展,钢筋的屈服程度决定了混凝土的裂纹扩展和多次冲击的剩余承载力。5.基于颗粒元-有限差耦合方法,建立无粘结预应力混凝土梁冲击试验仿真模型,其中混凝土颗粒单元和钢筋杆单元在锚固点交互作用,对混凝土损伤断裂和钢筋屈服进行模拟,并与试验结果进行了比较研究。表明颗粒元-有限差耦合模型适用于钢筋-混凝土类复合材料的动力特性与破坏机理研究。6.基于颗粒元模型对混凝土进行动力弯曲模拟,解释了初始静载影响的力学机理。对力链、裂纹发展和能量过程进行分析,揭示当初始静载水平处于静力线弹性阶段时,动力强度随初始静载增加,初始静载处于静力线弹性极限时,动力强度最大;而当初始静载处于静力的损伤软化阶段时,初始裂纹的产生使结构产生损伤,动力强度下降。
[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.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU528

【相似文献】