钢筋混凝土结构改进型分离式数值模型

提出一种考虑粘结滑移效应的钢筋混凝土改进型分离式数值模型。在混合物理论基础上，该模型兼顾混凝土基体和钢筋的力学行为，且基于钢筋混凝土界面粘结滑移模型，获得了钢筋等效模型。改进型分离式数值模型由于对钢筋及其界面无显式离散要求，使得钢筋的运用完全独立于其几何形状，同时对混凝土网格没有约束，并且不增加计算成本，因此该模型可适用于钢筋混凝土宏观结构层面分析。通过钢筋混凝土构件-结构的爆炸实验，对改进型分离式数值模型进行层次化验证。对比结果表明，考虑粘结滑移效应的有限元模型能够更好地预测钢筋混凝土结构的宏观力学行为。

Modified discrete numerical model for reinforced concrete structures

The interaction between rebar and concrete must always be considered to well describe and predict the mechanical behavior of reinforced concrete (RC) structures. A common way to model RC structures is by discrete reinforcements in finite element models where the discrete reinforcements imply that bond conditions between rebar and concrete are perfect. In order to take into account the bond-slip phenomenon, a modified discrete numerical model for RC structures is presented in this paper. The model is formulated within the framework of the mixture theory, considering two phases corresponding to the matrix concrete and the reinforcement bars and incorporating bond-slip effects to the stress-strain relation of the latter by considering the bond-slip model recommended by CEB-FIB. A nonlinear equivalent stress-strain relation for discrete steel bars is generated by incorporating the bond-slip strain to the strain of bars. Based on this model, a comprehensive parametric study is accomplished to obtain the influence of the parameters, including the strengths of the concrete and steel bars as well as the diameter of bars on the modified stress-strain relation of the discrete steel bars. In comparison to the traditional discrete numerical model where interface elements are generated via connecting the degrees of freedom of the bars and concrete meshing, the new model allows for the slipping of the steel bars without explicit discretization of the steel bars and the steel/concrete interfaces. This fact makes it attractive for numerical simulation of concrete structures at the macrostructural level. Using a code JUST-PANDA that is developed in-house, the model is verified by the explosion experiments at the component level and the structural level respectively. The comparisons with experimental results show that the new model can provide a more reliable prediction of the concrete structural behavior due to the consideration of the bond-slip effects in the stress-strain relation of the discrete steel bars by means of a simple procedure.