双轴压应力作用下混凝土徐变特性研究

Research on Creep Characteristics of Concrete Under Biaxial Compressive Stresses

核电安全壳结构承受双向预压应力作用,已有的单轴应力状态徐变计算方法无法计算双向应力下的混凝土徐变变形。考虑双轴应力状态对徐变泊松效应及徐变函数的影响,首先构建了以应力比为参数的双轴徐变泊松比矩阵,基于B4单轴徐变理论模型发展了以Dirichlet级数为表达的双轴受压徐变函数。综合考虑泊松效应及材料黏弹性特性,提出了双轴受压应力下混凝土徐变非线性理论模型。通过计算与试验结果的对比,验证了模型的准确性。最后将该模型应用于预应力损失分析,为服役核电安全壳预应力时变性损失分析及结构延寿性态评估提供了参考。

The structures of nuclear containment vessel usually work under biaxial pre-compressive stresses.The existed uniaxial creep theory cannot be used to calculate the creep deformation of concrete under biaxial compressive stresses.Considering the effect of biaxial compressive stresses,the matrix of creep Poisson’s ratio was established by introducing the parameter of stress ratio.Meanwhile,based on the B4 creep model of uniaxial stress,the creep function under biaxial stresses was developed using Dirichlet series.Combining the Poisson effect with material viscoelastic property,the nonlinear creep model under biaxial compressive stresses was proposed.The proposed model was verified by taking the comparison between numerical and experimental results.Finally,the proposed model was also employed to numerically analyze the pre-stress loss for a containment vessel.It is expected that the proposed model could be useful for the containment vessel structures on assessment of time-dependent prestress loss and prediction of further working life.