混凝土率型内时损伤本构模型

Rate-dependent endochronic damage constitutive model for concrete

混凝土是一种典型的率敏感材料,为了更好地描述混凝土结构在动力、冲击荷载作用下的强度和变形特征,本文结合内时理论和损伤理论建立了一种考虑混凝土率效应的内时损伤本构模型。该模型的特点:将混凝土材料的受力软化效应分解为密实状态的塑性效应和由微裂缝扩展引起的刚度退化效应。前者由内时理论来描述,这使该模型摆脱了一般弹塑性模型中屈服面的概念,从而更符合混凝土的变形特性,并且简化了非线性计算过程;后者由损伤理论来描述,根据混凝土的动力试验结果建立了增量型的损伤演变方程,从而使该模型能够较好地反映混凝土的动力特性。最后,应用本文建议的模型对一钢筋混凝土简支梁进行了非线性分析,结果表明:当结构承受快速荷载作用时,应变率对结构的受力性能影响较大,在进行结构分析时必须予以考虑。

Concrete is a type of rate-dependent material. In order to describe the strength and detormanon characteristics of concrete under impact loads,an endochronic damage constitutive model with the effect of strain rate taken into account is proposed. In this model,the elasto-plasticity of concrete is described by endochronic theory,so that the concept of the yield surface is not needed. And the behavior of stiff- ness degeneration due to microcrack propagation is described by damage theory. Based on the dynamic experiments,incremental evolvement law of damage is introduced. The comparison of numerical and ex- perimental results shows that the model can well represent the uniaxial and biaxial dynamic behavior of concrete. Finally,the proposed model is used to analyze a simply supported beam loaded by an impact dis- placement load at the middle of the span. The analyzing result shows that the strain rate dependence of the material can have a great effect on the strength and stiffness of concrete structures subjected to im- pact loads.