基于环境与荷载因素的混凝土率效应及破坏机理试验研究

发布时间：2018-06-28 22:37

本文选题：混凝土 + 率效应　；参考：《武汉理工大学》2013年博士论文

【摘要】：混凝土结构的强度、刚度和延性会受到加载速率的变化而产生显著影响,因而混凝土率效应特性和破坏机理也成为抗震安全评价中的关键性因素之一。本文在大量试验基础上对混凝土材料的率效应及其发生机理进行了系统的研究。利用三轴仪对混凝土在水饱和状态、有加载历史和双向受压状态下进行了动态抗压试验,对CT图像进行了破坏机理分析,累计完成247个试件的加载试验,共获取168组有效数据。主要研究内容如下：第一,研究了水环境对混凝土率效应特性的影响。对大气自然湿度状态下的混凝土和水饱和混凝土在10-5/S、5×10-5/s、10-4/S、5×10-4/S应变速率下进行单轴抗压试验与4MPa、8MPa两种围压下的常三轴抗压试验,分析了在不同应变速率、不同围压下大气自然湿度状态和水饱和状态下的混凝土强度、变形特性及弹性模量等物理力学参数及性能的变化特性,并就水介质对混凝土率效应特性的影响程度与规律给出了明确结论,建立了三轴强度率效应经验公式。第二,研究了不同荷载类型与加载历史对混凝土率效应特性的影响。对预静载历史和预循环加载历史的混凝土试件在同应变速率下进行单轴抗压试验,对比分析在不同预静载加载历史、预循环加载历史和应变速率下混凝土的峰值应力、峰值应变以及弹性模量等的变化规律。在高应变速率(10-3/s)作用下,加载历史对混凝土强度的影响作用减弱,当预静态加载历史幅值为60%的极限抗压强度时弹性模量达到最大值。在低应变速率(10-5/S)作用下,循环加载历史对混凝土强度的劣化更加明显。第三,研究了单双向应力状态下混凝土的率效应特性。对大尺度混凝土试件进行了10-5/S、10-4/S和10-3/s应变速率下单轴压缩试验和在一向侧应力为0MPa、8.3MPa、5.6MPa、8.3MPa下的双轴压缩试验,对比并分析了混凝土的单轴受压和混凝土在不同侧应力下强度、变形特性以及弹性模量等力学性能,对其变化规律给出明确结论。第四,基于CT图像分析了混凝土的破坏机理。通过CT实时对混凝土试件横断面在不同加载阶段进行了11次扫描和第9、10、11次加载进行了从外向里的切面扫描,分析了混凝土的破坏机理。对水饱和混凝土动态损伤与破坏形态从细观层面给出了清晰的描述,对其损伤与破坏机理给出了明确的解释。
[Abstract]:The strength, stiffness and ductility of concrete structures will be significantly affected by the change of loading rate. Therefore, the concrete rate effect characteristics and failure mechanism have become one of the key factors in seismic safety evaluation. Based on a large number of experiments, this paper systematically studies the rate effect of concrete material and its occurrence mechanism. The dynamic compression tests of concrete under water saturation, loading history and biaxial compression were carried out by using a triaxial apparatus. The failure mechanism of CT images was analyzed. The loading tests of 247 specimens were completed, and 168 effective data were obtained. The main contents are as follows: first, the effect of water environment on concrete rate effect is studied. Uniaxial compression tests and constant triaxial compression tests of concrete and water-saturated concrete under natural atmospheric humidity at 10 ~ (-5) / S ~ (-5) 脳 10 ~ (-5) / s ~ (-5) 脳 10 ~ (-4) S strain rate and 4 MPA ~ (8 MPA) confining pressure were carried out, and different strain rates were analyzed. Physical and mechanical parameters such as strength, deformation and elastic modulus of concrete under different confining pressures under natural humidity and water saturation, The influence degree and law of water medium on concrete rate effect characteristics are given, and the empirical formula of triaxial strength rate effect is established. Secondly, the influence of different load types and loading history on concrete rate effect is studied. Uniaxial compression tests of concrete specimens with prestatic loading history and precyclic loading history were carried out at the same strain rate. The peak stresses of concrete under different prestatic loading histories, precyclic loading histories and strain rates were compared and analyzed. The variation of peak strain and elastic modulus. Under the action of high strain rate (10 ~ (-3) / s), the effect of loading history on the strength of concrete is weakened, and the modulus of elasticity reaches the maximum when the historical amplitude of prestatic loading is 60% of the ultimate compressive strength. Under the action of low strain rate (10 ~ (-5) / S), the degradation of concrete strength by cyclic loading history is more obvious. Thirdly, the rate effect characteristics of concrete under single and two-way stress are studied. The axial compression tests of 10 ~ 5 / S 10 ~ (-4) / S and 10 ~ (-3) / s strain rate for large scale concrete specimens were carried out, and the uniaxial compression tests of concrete under uniaxial compression and the strength of concrete under different lateral stresses were compared and analyzed. The deformation characteristics and elastic modulus of mechanical properties are discussed. Fourthly, the failure mechanism of concrete is analyzed based on CT images. The concrete cross-section was scanned by CT in real time at different loading stages, and the concrete failure mechanism was analyzed. The dynamic damage and failure form of water-saturated concrete is described clearly from the meso level, and its damage and failure mechanism is explained clearly.
【学位授予单位】：武汉理工大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TU528

【引证文献】