混凝土单轴受拉的非局部本构模型

混凝土受拉本构行为存在很强的局部软化现象,使得单轴受拉试验无法给出应力-应变关系,而只能给出应力-位移关系。本文根据内变量理论和等效应变假设建立了基于真实应变的混凝土单轴受力本构方程,并根据Weibull分布可以描述混凝土等脆性材料断裂过程的试验现象,建立了关于弹性应变的损伤演化规律。然后,通过假设平均应变与真实弹性应变的函数关系,在应力-平均应变的本构关系中采用平均弹性应变以描述其非局部行为,而在材料的损伤演化规律中采用真实弹性应变以描述其局部行为,由此建立了单轴受拉荷载条件下的非局部本构模型。最后,对一个单调受拉试验和一个反复受拉试验的仿真结果表明所提出的非局部本构模型可以准确地模拟试验结果。

A Non-Local Constitutive Model for Concrete under Uniaxial Tension

It is not stress-strain relation but the stress-displacement relation ship that can be obtained in an experiment of concrete under uniaxial tension due to its severe local softening behavior.According to intrinsic variable theory and equivalent strain assumption,a damage constitutive equation in terms of real strain was established for concrete under uniaxial tension, while damage evolution rule was set up based upon the fact that the Weibull distribution could be used to describe the fracture process of brittle materials,such as concrete.Furthermore,with an assumed relation between mean strain and real elastic strain,a non-local constitutive model was obtained by employing mean elastic strain to capture the non-local behavior of stress-mean strain constitutive relation as well as adopting real elastic strain to follow the local behavior of damage evolution process.The proposed non-local model was finally shown to simulate successfully the experiment results of a concrete specimen under uniaxial monotonic tension and another one under uniaxial cyclic tension.