基于统计损伤理论的混凝土应力-应变行为

Stress-Strain Behavior of Concrete Based on Statistical Damage Theory

基于统计损伤理论,从有效应力的角度阐述了混凝土损伤演化累积诱致灾变的整个过程,分析了细观损伤机制与宏观力学行为之间的内在联系;建立了考虑强度等级影响的混凝土单轴拉伸、压缩统计损伤模型,该模型考虑断裂和屈服2种细观损伤模式,分别与微结构的“劣化”和“强化”机制相对应;同时区分峰值名义应力状态和临界状态,并将临界状态作为损伤局部化的前兆.结果表明:所建立的模型能够预测不同强度等级(C20~C80)混凝土的单轴拉伸、压缩宏观应力应变行为,并能够反映强度等级对混凝土细观损伤演化过程的影响规律;随着强度等级的提高,表征细观断裂和屈服损伤演化过程的特征参数展现出明显规律性的变化趋势;细观损伤机制最终决定了混凝土宏观非线性的应力应变行为,屈服损伤模式在整个过程中起决定性作用.

Based on statistical damage theory,the whole process of concrete damage evolution cumulative induced catastrophe was elaborated in detail from the perspective of effective stress,the internal relation between mesoscopic damage mechanism and macro-mechanical behavior was analyzed.A statistical damage model of concrete under uniaxial tension and compression considering the influence of strength grade was established.Two mesoscopic damage models for fracture and yield were considered in the model,which was corresponded to the“deterioration”and“strengthening”mechanisms of microstructure respectively.The peak nominal stress state was distinguished from the critical state,and the critical state was used as the precursor of damage localization.The analysis results show that the model can predict the macroscopic stress-strain behavior of concrete with different strength grades(C20-C80)under uniaxial tension and compression,and can reflect the influence law of strength grade on the mesoscopic damage evolution process of concrete.With the increase of strength grade,the characteristic parameters of the evolution process of mesoscopic fracture and yield damage show significantly regular change trend.The mesoscopic damage mechanism ultimately determines the macro-nonlinear stress-strain behavior of concrete,and the yield damage mode plays a decisive role in the whole process.