考虑冻融劣化效应的混凝土单轴压缩统计损伤模型

THE STATISTICAL DAMAGE MODEL OF CONCRETE UNDER UNIAXIAL COMPRESSION CONSIDERING FREEZE-THAW DETERIORATION EFFECT

  • 摘要: 该文建立了考虑冻融劣化效应的混凝土单轴压缩统计损伤本构模型,将整个压缩过程分为均匀损伤和局部破坏两个阶段,考虑细观屈服和断裂两种损伤模式。在冻融环境下,混凝土内部孔隙结构形态和微结构的力学特征会产生显著的变化,可由初始弹性模量E反映;在进一步承受压缩荷载过程中,微结构内部微裂纹萌生/扩展的形态、路径和数量也会由于初始冻融劣化的影响发生相应的改变,可由损伤参数εaεhεbH表征。假设不同冻融循环次数情况下,混凝土微结构力学性能和细观损伤过程的演变趋势服从某种规律性,将上述5个特征参数定义为冻融循环次数N的函数。为验证模型的合理性,该文开展了混凝土单轴压缩试验,获得冻融循环次数N为0次~150次时对应的单轴压缩应力-应变全曲线,同时分析了文献中的5组试验数据。结果表明:预测曲线与试验曲线吻合较好,模型中的特征参数随着冻融循环次数的增加表现出明显的规律性。该模型为冻融环境下混凝土损伤机制分析和预测提供了有效工具。

     

    Abstract: A statistical damage constitutive model of concrete under uniaxial compression is proposed to consider the impact of freeze-thaw. The entire compression process is divided into two stages: uniform damage and local failure, considering two mesoscopic damage modes of yield and fracture. Under the freeze-thaw environment, the internal pore structure and the mechanical characteristics of the microstructure will change significantly, which can be reflected by the initial elastic modulus E. In the process of further bearing the compressive load, the shape, path and quantity of microcracks initiation and propagation in the microstructure will also change due to the influence of the initial freeze-thaw degradation, which could be characterized by damage parameters εa, εh, εb and H. Assuming that under different number of freeze-thaw cycles, the evolution trend of the mechanical properties of the microstructure and the meso-damage process obey a certain regularity, thusly define the above 5 characteristic parameters as functions of the number of freeze-thaw cyclesN. To verify the rationality of the model, the uniaxial compression test was carried out, and the stress-strain full curves of concrete were obtained when the number of freeze-thaw cycles N changed from 0 to 150. Meanwhile, five groups of experimental data in the literature were also analyzed. The results show that: prediction curves are in a good agreement with the test curves, and the characteristic parameters in the model show obvious regularity as the number of freeze-thaw cycles increases. This model provides an effective tool for both the analysis and predicting damage mechanism of concrete in the freeze-thaw environment.

     

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