混凝土材料三维统一硬化/软化弹塑性本构模型

A 3D unified hardening/softening elastoplastic constitutive model for concrete

混凝土材料的弹塑性本构模型通常采用剪切型屈服面,剪切型屈服面包括两种硬化方式,即黏聚力(c)硬化和摩擦角(?)硬化.目前大多数本构模型都采用c硬化模式,无法反映应力诱导各向异性.本文的屈服函数是由混凝土材料非线性统一强度准则发展而来,采用φ硬化模式.基于Sargin提出的单轴压缩应力应变关系,提出一个统一硬化/软化参数,即硬化和软化参数具有相同的表达式.将提出的硬化/软化参数与屈服函数相结合,发展了混凝土材料三维统一硬化/软化弹塑性本构模型.该模型能够统一地描述混凝土的硬化/软化,避免了循环加载中再加载过程中硬化或软化参数的判断,从而增加了计算效率.模型有效地确定了塑性势参数,使得建立的本构模型能够合理地控制混凝土的剪胀.建立了峰值应力对应的等效塑性剪应变与围压的关系,使得建立的模型能够描述混凝土材料的应变软化随围压的变化规律.通过与普通强度和高强混凝土的双轴和真三轴试验结果比较表明,建立的模型能够适用于不同类型的混凝土材料,并且能够合理地描述混凝土材料的变形和强度特性.

The elastoplastic constitutive model for concrete material often employs the shear yield surface which includes two kinds of hardening modes, namely, cohesion （c） hardening and friction （q~） hardening. Most of existing constitutive models employed c hardening mode which is not able to reflect the stress induced anisotropy. The yield surface in this paper is developed by nonlinear unified strength criterion for concrete, and the fo hardening mode is used. A unified hardening/softening parameter is proposed on the bases of the uniaxial compressive stress-strain relation proposed by Sargin. Then a 3D unified hardening/softening elastoplastic constitutive model is established by combing the hardening/softening parameter with the yield surface. The developed model is capable of describing the hardening and softening uniformly. Therefore, the computational efficiency of numerical analysis is increased. The model gives the determination of the plastic potential parameter, which makes the dilatancy can be controlled reasonably. Moreover, the relationship between the equivalent plastic shear strain related to the peak stress and confining pressure is supposed by the test results. Thus the model can reasonably describe the change rules of strain softening of concrete with the confining pressure. Comparisons with the biaxial and triaxial tests of high strength and normal strength concrete indicate that the proposed model is suitable for various kinds of concrete materials, and can reasonably describe the 3D deformation and strength properties of concretes.