考虑温度影响的混凝土弹塑性本构模型及其应用

The elasto-plastic constitutive model of concrete including effects of temperature and its application

基于弹塑性理论的框架,引入热力学中的自由能概念,建立了考虑温度影响的混凝土弹塑性本构模型。假设混凝土为弹塑性解耦材料,通过采用包含温度的自由能函数建立了弹性应力-应变关系的表达式;基于Drucker-Prager强度准则构造屈服函数,以塑性剪应变作为硬化参量,通过在硬化规律中引入温度变量来反映温度对混凝土塑性性质的影响,得到了塑性应力-应变关系的表达式。基于ABAQUS有限元软件平台,应用半隐式回映算法编制了上述弹塑性本构模型的UMAT子程序,完成了该模型的程序实现。通过对C20及C40混凝土单元在不同温度条件下单轴压缩与双轴压缩的数值模拟,并将模拟结果与已有文献试验结果进行了对比,二者符合较好,验证了该模型的正确性。应用该模型模拟混凝土材料的力学特性,开展了不同温度下集中荷载作用的混凝土简支梁及混凝土轴心受压柱力学响应的数值模拟。计算结果表明,随着温度的升高,相同荷载作用下混凝土构件的力学响应逐渐增大,反映了混凝土材料的力学性能随着温度的升高逐渐退化,这符合不同温度条件下混凝土构件力学响应的基本规律。

Based on the elasto-plastic theory and the concept of free energy in the thermodynamics,an elasto-plastic constitutive model of concrete including effects of temperature is presented.The concrete is assumed as elasto-plastic decoupling material.The elastic stress-strain relation is derived from the free energy function including temperature.The yielding function is derived based on the Drucker-Prager strength criterion,and the plastic shear strain serves as hardening parameter.The temperature variable is included in the hardening law to reflect the effects of temperature on the plastic properties of concrete,and the plastic stress-strain relation is derived.The constitutive model is embedded into the finite element software ABAQUS.The semi-implicit return mapping algorithm is employed to compile the UMAT subroutine of the model.The numerical simulation of the uniaxial and biaxial compression of the C20 and C40 concrete elements are carried out with the developed constitutive model.The numerical results agree well with the corresponding test data.The developed constitutive model is applied to the numerical simulation of the mechanical response of concrete members at different temperatures,including the simply supported beam under the action of concentrated load and the axial compressive column.The numerical results show that the mechanical responses of concrete members to same loads increase with the raise of temperature.This indicates the degradation of mechanical properties of concrete with the raise of temperature and accords with the basic characteristics of the mechanical response of concrete members at different temperatures.