【作者】 尚世明；

【导师】 宋玉普；

【作者基本信息】 大连理工大学 ， 结构工程， 2013， 博士

【摘要】 混凝土是现代建筑中被广泛应用的建筑材料。动态荷载(如地震、冲击、爆炸、车辆荷载、海浪荷载、风荷载等)能够造成建筑物和构筑物的破坏甚至倒塌,造成财产和生命的损失。混凝土结构的动力复杂受力分析是结构设计中的难点,例如框架结构的节点、核安全壳、混凝土拱坝等处于复杂应力状态的结构。我国处于环太平洋与欧亚地震带之间,是地震多发国家。现有的混凝土多轴动态性能研究成果中,单轴动态性能研究比较多,多轴动态性能研究比较少；爆炸、冲击荷载作用下混凝土性能研究比较多,地震荷载作用下(应变率范围10-5s-1-10-2s-1)混凝土性能研究比较少。因此,地震荷载作用下,多轴应力状态下混凝土的动态性能研究具有非常重要的意义。本文采用大连理工大学研制的三轴静、动液压伺服试验机,开展了一系列的混凝土单轴和多轴动态试验。应力组合方式包括：单轴压、单轴拉、定侧压双轴抗压、双轴比例抗压、双轴拉压和三轴抗压；应变率分别为：10-5s-1、10-4s-1、10-3s-1和10-2s-1。利用ABAQUS提供的用户自定义材料模块,编写了混凝土内时损伤动态破坏模型程序,建立了与本文部分试验相应的数值模型,进行了数值计算。主要研究内容如下：1开展了混凝土单轴抗压、单轴抗拉动态性能试验,获得了试件的破坏形态,单轴压、拉动态强度,峰值荷载处的应变,单轴抗压峰值荷载处的割线模量,得到了单轴抗压、单轴抗拉强度与应变率的关系,获得了不同应变率下的单轴抗压、单轴抗拉应力-应变曲线。2开展了定侧压双轴抗压和双轴比例抗压动态性能试验,获得了试件的破坏形态、双轴抗压动态强度和竖向峰值应变；获得了竖向荷载引起的侧向峰值应变、由竖向荷载引起的泊松比；讨论了比例加载与非比例加载两种加载方式对混凝土双轴抗压强度的影响；探讨了混凝土双轴受压强度提高的机理；从侧向变形的角度解释了双轴抗压强度随中间主应力变化的原因；建立了考虑应变率影响的混凝土双轴抗压动态破坏准则。3开展了定围压三轴抗压动态性能试验,获得了试件的破坏形态、三轴抗压动态强度和竖向峰值应变;得到了三轴抗压动态强度的计算公式；比较了竖向单调加载和竖向循环加载时混凝土的三轴抗压强度；研究了定围压三轴抗压动态荷载下混凝土的能量耗散和混凝土的损伤。4开展了定侧拉双轴拉压动态性能试验,获得了试件的破坏形态、双轴拉压动态强度和拉、压方向上的峰值应变。得到了双轴拉压强度及峰值应变随侧拉应力和应变率的变化规律。建立了考虑应变率影响的双轴拉压动态破坏准则。5建立了在单轴、二轴及三轴应力状态下,应变率范围为10-5s-1-10-2s-1的八面体应力空间的混凝土动态破坏准则。为了工程上的实用性,给出了拉、压子午线的上限值、下限值和平均值。6在本文建立的多轴动态强度破坏准则和内时损伤动态本构模型的基础上,利用ABAQUS中的用户自定义材料模块(UMAT),建立了与本文试验相应的数值模型并进行了数值计算,验证了自定义混凝土材料模型与本文试验结果是吻合的。更多还原

【Abstract】 Concrete is a widely used construction material in modern architectures. Dynamic load (such as earthquake load, impact load, explosion load, vehicle load, waves load, wind load, etc.) can cause the damage and collapse of buildings, which can lead to casualties and property losses. In structure design, it is a difficult point to the analyses of complex dynamic force, such as the force analyses of beam-column connections, nuclear containments and concrete arch dams. Since China lies in the earthquake belt along the west of the Pacific Ocean, She is a multi-earthquake-happening country. In existing research results, the works of uniaxial dynamic behavior are much more than these of multi-axial dynamic behavior, the works of concrete dynamic behavior under explosion load and impact load are much more than these of earthquake load. Therefore, it is very important to study the dynamic behavior of concrete under multi-axial stress.A series of concrete multi-axial dynamic tests are carried out by the triaxial static and dynamic testing machine. The tests include several stress states:uniaxial compression, uniaxial tension, biaxial compression with constant lateral pressure, biaxial proportional compression, triaxial compression, biaxial tension-compression. The strain rates were10-5s-1,10-4s-1,10-3s-1and10-2s-1. In the UMAT of ABAQUS, the program of concrete endochronic damage constitutive model is written. The corresponding numerical models are established, and the numerical calculations are carried out.The main research contents are as follows:1Uniaxial compression and uniaxial tension dynamic tests are carried out. Specimen failure modes, dynamic strength, peak strain and the secant modulus at peak load are obtained. The relationships between the uniaxial strength and strain rates are obtained. Stress-strain curves are obtained.2The tests of biaxial compression with constant lateral pressure and biaxial proportional compression are carried out. Specimen failure modes, biaxial compressive dynamic strength, vertical peak strain are obtained. Lateral peak strain and the poisson ratio are obtained, which are caused by vertical load. The influence of loading paths on biaxial compressive strength is discussed, and the loading paths include biaxial proportional compression and biaxial compression with constant lateral pressure. Under biaxial compression, the mechanism of strength increase is discussed. From lateral deformation, the reason of biaxial compressive strength changing with middle principal stress is explained. The dynamic failure criteria are respectively established.3The tests of triaxial comprssion are carried out. The specimen failure modes, the triaxial compressive dynamic strength, the vertical and lateral peak strain are obtained. The formulas of triaxial dynamic strength are obtained. The strengths of monotonic loading and cyclic loading in vertical direction are compared. Under triaxial compressive dynamic loading, energy dissipation of concrete and damage of concrete are researched.4The tests of concrete biaxial dynamic tension-compression are carried out. Specimen failure mode, the tensile-compressive dynamic strength, the peak tensile strain and the peak compressive strain are obtained. The changing rules of strength or strain with strain rates and lateral tensile stress are obtained. The dynamic criterion under tension-compression is established.5Using the testing data of this paper, in octahedral space, the multi-axial dynamic criterion is established, in which the range of strain rates is10-5s-1-10-2s-1. For the usability of engineering, three groups of parameters of tensile meridian and compressive meridian are given, which respectively are upper limit, average and lower limit.6Based the multi-axial dynamic failure criterion and endochronic damage constitutive model, using UMAT of ABAQUS, the numerical computations are carried out, and the results prove that the material model is agreeing with the testing results of this paper.更多还原