【作者】 曹伟；

【导师】 宋玉普；

【作者基本信息】 大连理工大学 ， 结构工程， 2004， 博士

【摘要】 混凝土结构的疲劳是一个广为关注的问题，本文针对这一问题结合国家自然科学基金项目——混凝土多轴变幅疲劳破坏准则(50078010)的研究，利用自制的试验加载装置完成了两向定侧压约束下混凝土三轴受压、三轴拉-压等幅和变幅疲劳试验，对试验结果进行了分析。并在此基础上确定了疲劳变形定量化规律和疲劳强度计算方法；比较全面深入地描述了混凝土多轴疲劳损伤机理和劣化规律，建立了疲劳剩余寿命预测方法和疲劳本构模型，为混凝土结构的疲劳设计和分析提供了基础。本文共分如下七章： 第一章是绪论，阐述了本课题的选题背景和意义；系统地综述了混凝土疲劳试验和理论研究的当前国内外发展现状，在此基础上提出了本文的工作和内容。 第二章简要地介绍了本文三轴疲劳试验装置，进行了两向等侧压约束下混凝土立方体试件三轴受压等幅和变幅疲劳试验，分析了三轴受压疲劳破坏机理，给出了相应的疲劳破坏试验判断标准；得到了混凝土在两向侧压约束下单级和多级受压疲劳的变形发展规律，包括最大(最小)纵向应变、残余应变、最大纵向应变率和疲劳变形模量等随循环次数的发展规律以及疲劳损伤的演变规律，并给出了相应的经验公式。 第三章根据本文定侧压下三轴受压疲劳试验数据，并结合已有的单轴受压和双轴受压疲劳试验结果，建立了综合考虑侧压应力水平和疲劳应力比的统一S-N曲线方程，得到了混凝土多轴受压疲劳强度；分析了从混凝土初始极限强度概率分布出发和疲劳寿命概率分布出发来计算混凝土条件疲劳极限强度的一致性原理，从而为应用小样本常规疲劳试验结果计算条件疲劳极限强度提供了理论和方法。 第四章进行了两向等侧压约束下变截面混凝土棱柱体试件的三轴拉-压等幅和变幅疲劳试验，分析了三轴拉．压疲劳破坏机理和破坏形态；建立了综合考虑侧压应力水平和疲劳荷载的统一S-N曲线方程；得到了混凝土在两向定侧压约束下三轴拉．压疲劳变形发展规律，包括循环应力．应变特性、纵向应变、第二阶段应变率、疲劳变形模量和损伤等演变规律，并给出了相应的经验公式。 第五章综合评价了已有的各类混凝土非线性累积损伤模型的特点和适用性，并应用非线性动力学观点论证了经典Miner线性累积损伤准则在预测疲劳剩余寿命方面的固有缺陷；在考虑加载历史对疲劳寿命的影响下，建立了描述混凝土累积损伤的非线性模型；并根据损伤等效原理给出了混凝土疲劳剩余寿命的预测方法和步骤。 第六章讨论了混凝土材料静力加载和疲劳加载下的特性；在综合考虑塑性和脆性相结合的复杂性质基础上，运用损伤理论和塑性理论在应变空间分别建立了一个能描述混凝土应变和刚度变化的损伤面和塑性面，应用有效应力和弹塑性耦合的概念来描述混凝土的多轴疲劳本构特征。 第七章为结论和展望，总结了本文完成的主要成果和相应结论，指出了在本文研究基础上需要进一步开展的几个问题。更多还原

【Abstract】 It is widely concerned in fatigue of concrete structures. In this paper, concrete triaxial compression fatigue experiments and tension-compression fatigue experiments with constant confinements in two lateral directions have been carried out using a self-modified loading apparatus. Based on the analysis of the test data, the quantitative principles of concrete fatigue deformation and the calculation method of fatigue strength are determined. Moreover, the multi-axial fatigue damage mechanics and process are discussed more extensively, and a nonlinear cumulative damage model to predict the remaining fatigue life and a constitutive model to describe concrete fatigue characteristics are established. The thesis is an important part of the project of National Natural Science Foundation-Fatigue failure criterion of concrete under multi-axial variable-amplitude fatigue loading (No. 50078010), the contents of which include seven chapters as follows.The first chapter is preface. It expounds the significance of this study and the relevant literatures. Meanwhile the historical and present background of the research on experiment and theory of plain concrete is introduced systematically. Based on the information, the objectives of this paper are put forward.The second chapter introduces the test system simply at first. Then an experiment is carried out on concrete cube specimens to investigate the deformation characteristics of plain concrete under triaxial constant-amplitude and variable-amplitude compression fatigue loading with constant confinement in two lateral directions. The damage mechanics under multi-axial compressive fatigue loading is analyzed and the damage criterion is determined. The deformation characteristics including the development of the maximum/minimum longitudinal strains, the residual strain, the maximum longitudinal strain creep rate, the deformation modulus and the damage cumulation of concrete in terms of cyclic number are gained. In addition, some experience formulas for them are regressed.The third chapter establishes a unified S-N curve equation to calculate multi-axial fatigue ultimate strength of concrete considering both the effect of confinement and minimum/maximum stress ratio, based on the triaxial fatigue test data in this paper and the test results under uniaxial and biaxial fatigue loading in previous literatures. Moreover, the consistency of calculating condition fatigue ultimate strength with fatigue life distribution and initial ultimate strength distribution is analyzed. Thus the calculation of condition fatigue ultimate strength using common fatigue experiment with small samples is available.The fourth chapter carries out the triaxial tension-compression fatigue experiments on tapered prism specimens subjected to constant-amplitude and variable-amplitude fatigue loading with constant confinement in two lateral directions. The damage mechanics and failure mode are analyzed. A unified S-N curve equation to calculate tension-compression fatigue ultimate strength of concrete is established. In addition, the deformation characteristics including the development of the cyclic stress-strain curve, the longitudinal strains, the secondary stage strain rate, the deformation modulus and the damage cumulation of concrete in terms of cyclic number are obtained.The fifth chapter reviews the applicability and characteristics of previous nonlinear cumulative damage models synthetically, and the inherent limitation of Miner’s rule onpredicting remaining fatigue life is also proofed from the point of view of the nonlinear dynamic. Taking into account of the effect of loading history, a new nonlinear cumulative damage model is established and the steps to predict remaining fatigue life with the model is given.The sixth chapter discusses the characteristics of concrete under static and fatigue loading in detail. Considering the complicated characteristics of plasticity and brittleness, a two-surface model is established. The so-called two surfaces are a damage surface established by the co更多还原