【作者】 冀晓东；

【导师】 宋玉普；

【作者基本信息】 大连理工大学 ， 结构工程， 2007， 博士

【摘要】 处于寒冷地区的钢筋混凝土结构物常常发生冻融破坏，抗冻性能是钢筋混凝土耐久性能中非常重要的方面。冻融循环作用后，混凝土的抗冻性能和力学性能发生退化，钢筋与混凝土的粘结性能也遭到破坏，研究冻融循环作用后混凝土的力学性能和钢筋混凝土的粘结性能具有十分重要的工程意义。本文通过试验研究和理论分析，主要完成了以下工作：1、试验研究了尺寸为100×100×100mm的混凝土小试件冻融后的单双轴力学性能和抗冻性能，并试验研究了尺寸为150×150×150mm的混凝土标准试件冻融后的单轴力学性能。分别建立了两种混凝土试件的各力学指标与冻融循环作用次数的关系公式，并建立了冻融后混凝土小试件与标准尺寸混凝土试件的强度转换计算公式。通过双轴强度试验数据分析，研究了冻融循环作用对混凝土双轴压作用下强度和变形的影响。采用统一的应力-应变方程形式来表示混凝土遭受冻融循环作用后的本构关系。2、基于各向同性连续损伤力学理论，以损伤条件下的弹性模量和泊松比为变量，基于Ottosen理论模型建立了混凝土冻融损伤破坏准则，并以Ottosen本构理论模型为基础，利用建立的冻融损伤破坏准则构建了混凝土冻融损伤本构模型，并编制了本构模型有限元程序，为有限元计算应用提供参考。3、试验研究了冻融循环作用后两种外形、三种直径、三种粘结长度的钢筋与混凝土的粘结性能，分析了冻融循环对钢筋粘结性能的影响，并分析了设定冻融循环次数作用后钢筋外形、钢筋直径、钢筋粘结长度和混凝土强度对钢筋与混凝土粘结锚固性能的影响。4、把钢筋混凝土粘结滑移曲线分为四个阶段，分别对光圆钢筋和不同直径、不同粘结长度的螺纹钢筋的粘结滑移曲线随着冻融循环作用次数的增加而变化作了较详细的分析，从试验角度分析了冻融后钢筋和混凝土粘结性能的退化机理。基于细观力学模型建立了冻融后钢筋混凝土界面层受冻时的静水压力理论计算公式，从细观力学角度分析了冻融后光圆钢筋粘结性能迅速退化的机理。通过钢筋与混凝土界面层的粘结-摩擦力学模型分析，揭示了光圆钢筋与混凝土粘结试件在冻融循环作用后，粘结强度迅速下降的本质原因，并解释了光圆钢筋粘结滑移曲线的不同阶段随着冻融循环作用次数增加而变化的机理。通过弹塑性厚壁圆筒理论计算模型，建立了钢筋粘结强度理论计算公式，并通过与试验得到的粘结强度相比较，从理论上揭示了在试验中发生的螺纹钢筋粘结试件在遭受一定冻融循环次数作用后，拔出破坏形态发生变化的机理。5、基于三参数weibull分布，在理论分析的基础上建立了混凝土结构冻融损伤可靠度分析模型，认为混凝土结构遭受冻融循环作用的正负峰值温度差是随机变化的，把混凝土结构冻融损伤近似看作不同正负峰值温度差顺序作用损伤累积的结果，利用等效损伤原理，推导了计算混凝土冻融损伤失效概率计算公式。得出了混凝土结构冻融损伤剩余寿命的计算公式，并结合混凝土冻融的定量化分析，得出了在遭受一定的冻融损伤后混凝土结构的剩余工作年限。更多还原

【Abstract】 The concrete structures located in the cold region usually are destroyed because of freezing and thawing, and frost resistance is an important aspect of,durability of concrete structure. The frost resistance and mechanic performance of concrete and the bond behaviour between concrete and steel bar will be destroyed after freezing and thawing. It is very important for concrete structure to research the bond behaviour between concrete and steel bar after freezing and thawing. In this paper, the major contributions are summarized as follows by experimental research and theoretical analysis.1、The uniaxial、biaxial mechanic performance of concrete cubic specimens with a size of 100×100×100mm and uniaxial mechanic .performance of concrete cubic specimens with a size of 150×150×150mm are tested after freezing and thawing. The relationship equations between strength of two kinds of concrete specimens and cycles of freeze-thaw cycling are estimated. And the relationship equation of concrete strength of two kinds of specimens is estimated, too. A standard equation is used to descript the stess-strain curve of concrete after freezing and thawing.2、Based on the damage mechanics and Ottosen failure model, a frost damage failure model is established which elastic modulus and Possion ratio under damage are the damage variable. And based on Ottosen theory, a frost damage constitutive model is established and all these will be useful to the development of finite element programme. The test of the constitutive model by the experimental data shows that it is accurate comparatively.3、The pullout specimens of two different surface configurations, three different diameters and three different bond lengthes of stell bars are tested after freezing and thawing by experiments. The effect of freezing and thawing on the bond behaviour is analyzed through the study of these indexes, such as bond strength, slippage at the peak of bond strength, etc. And the effect of surface configurations, diameter of steel bar, bond length of steel bar and concrete strength on the bond behaviour between concrete and steel bar are analized based on the experimental results.4、Theτ-S curves of all pullout specimens are parted four segments to analyze the development ofτ-S curves with the cycles of freezing and thawing increasing. A formula is established to calculate the hydraulic pressure when the concrete under thawing based on the microcosmic mechanic model. Based on the bond-friction model of interface of concrete and steel bar, the mechanism of decreasing quickly of bond strength of plain steel bar after freezing and thawing. Based on the thick-walled column theory, the theoretic model of bond strength of deformed steel bar is obtained. The mechanism of the conversion of failure modes of pullout specimens after freezing and thawing is explained through analyzing the results of experiments and caculating results.5、Based on the theory of macro-damage mechanics, the damage of concrete structures under the action of freezing and thawing may be approximately regarded as the damage due to sequential cyclic action with various positive-negative peak temperature differences, since the temperature difference is always not a constant. On this basis, the reliability of damaged concrete is analyzed. The failure of concrete can be described by the Weibull distribution model. Thereby, a model with 3 parameters for analyzing the reliability of concrete is proposed and the formula for evaluating the residual life of concrete after the freezing-thawing action is deduced.更多还原