基于修正混凝土塑性损伤模型的大应变FRP约束混凝土有限元分析

精确的有限元分析(FEA)依赖于材料的准确定义。通过编写用户子程序UMAT实现了大断裂应变纤维增强聚合物(LRS FRP)在纤维方向上拉伸特性的定义。基于Abaqus中混凝土塑性损伤模型的理论框架，提出了一种改进的混凝土塑性损伤模型用于定义LRS FRP约束混凝土的材料特性。这些改进包括：通过LRS FRP约束混凝土的实验数据校准了与屈服准则相关的参数K；硬化/软化准则与约束刚度相关；流动法则与轴向塑性应变相关。采用修改后的材料模型进行FEA，结果表明：FEA预测的应力-应变曲线与实验结果吻合。基于FEA的结果，讨论了矩形柱截面上应力分布的不均匀性，根据约束效果可分为有效约束区域和弱约束区域，且在约束有效区域上应力分布不均匀性随着截面比(长边/短边)的增加而增加。

FINITE ELEMENT ANALYSIS ON LARGE-RUPTURE-STRAIN (LRS) FRP-CONFINED CONCRETE BASED ON MODIFIED CONCRETE DAMAGED PLASTICITY MODEL

Accurate finite element analysis (FEA) depends on the accurate definition of materials. The definition of material properties of large-rupture-strain fiber reinforced polymer (LRS FRP) in the fiber direction is realized by writing the user subroutine UMAT. Based on the theoretical framework of the concrete damaged plasticity model in Abaqus, a modified concrete damaged plasticity model is proposed to define the material properties of LRS FRP-confined concrete. These modifications include: the parameter K related to the yield criterion is calibrated by the test data of LRS FRP-confined concrete; the hardening/softening criterion is related to the confinement stiffness; the flow rule is related to axial plastic strain. The modified material model is used for FEA. The results show that the stress-strain curve predicted by FEA is consistent with the test results. Based on the FEA results, the non-uniform of stress distribution on the rectangular column section is discussed, which can be divided into effective confinement area and weak confinement area according to the confinement effect, and the non-uniform stress distribution in the effective confinement area increases with the increase of section ratio (the ratio of long side to short side).