混凝土材料三维弹塑性本构模型

非线性统一强度准则将材料的强度特性分解为4个相互独立的因素,由4个材料参数分别描述,在主应力空间内的强度面连续光滑,存在连续的偏导数.本文将非线性统一强度准则作为屈服函数,以塑性剪应变的函数作为硬化/软化参数,硬化/软化函数参考单轴压缩条件下的应力应变关系给出,建立了混凝土材料的非线性统一弹塑性本构模型.通过混凝土材料单轴、双轴和三轴试验结果对本构模型的验证,以及偏心受压构件试验结果对数值模拟结果的验证表明,所建立的非线性统一弹塑性本构模型可较好地描述混凝土材料的三维变形与强度特性,并可反映应变软化特性,将模型用于数值计算时易于获得收敛解,且具有较高的精确度和计算效率.

A three-dimensional elastoplastic constitutive model for concrete

Strength of concrete materials can be described by the theory of nonlinear unified strength criterion with four independent parameters. The failure surface of the strength criterion in the principal-stress space is smooth, and therefore it has continuous partial derivatives. The theory of nonlinear unified strength criterion is applied as a yield function, plastic shear strain is used as the hardening and softening parameters, and the hardening and softening laws are given by the stress-strain relationship under uniaxial compression. Then a three-dimensional elastic-plastic constitutive model for concrete is established. A user-defined material mechanical behavior（UMAT） is developed based on the finite element analysis software ABAQUS. The load resistance and the deformation capacity of a reinforced concrete column under eccentric compression are simulated using the present model. The present theoretical results are comparable to the available material-test data, and the numerical results have a good agreement with the experimental observations of the concrete column. This indicates that the developed constitutive model is capable of describing the strength and deformation behaviors, and representing the strain softening behavior of concrete under three-dimensional stress state. Furthermore, the model has high efficiency and accuracy in the numerical analysis.