钢筋混凝土构件滑移劈裂破坏机理的数值模拟

NUMERICAL SIMULATION on SLIPPING and SPLITTING PERFORMANCE in REINFORCED CONCRETE

钢筋混凝土是工程中常用的结构构件，其中，混凝土部分为一种组分复杂的非均质复合材料，对其力学特性的研究一直受到广泛关注。针对钢筋混凝土构件模型的混凝土部分，本文建立了三维的混凝土三相细观模型，借助骨料随机生成方法产生骨料的粒径及空间位置参数，并利用过渡区域在体现材料细观特性的前提下尽量减少单元总量，降低计算代价。针对钢筋与混凝土的界面黏结区域，本文建立了一套新型的钢筋混凝土界面粘结接触模型。模型在钢筋与混凝土的接触面间分别设置粘结单元和接触对来模拟钢混相互作用。在钢筋拉拔试验中，粘结单元与接触对协同工作能够有效地模拟变形钢筋与混凝土间的粘结滑移作厢，使得整个拉拔过程中力的传递更贴近实际，令数值模型及模拟结果具有更高的现实参考价值。在数值模拟过程中使用了基于Python语言的一体化脚本程序，极大提高了试验的可最复性和丁作效率。

Reinforced concrete is a kind of structural member widely apllied in engineering. The concrete part of RC is a complex heterogeneous composite material and the research on its mechanical properties has been widely concerned by scholars all over the world. Based on existing 2D three-phase mesoscopic concrete model, a 3D three-phase mesoscopic concrete model with spherical coarse aggregate is established. According to reality, the heterogeneity of the concrete material is considered in this model and the randomness of aggregate position in matrix is successfully simulated by means of the random delivery function. Besides, a transition region of mesh size is established between ITZ and other two phases with the purpose of decreasing the total amount of the unit under the premise that ensuring that the cracking process originating from ITZ can be simulated accurately.A solid model of deformed bar with ribs is established according to the actual experimental parameters, and cohesive elements are inserted between the contact surfaces along the bar＇s longitudinal direction. The interaction between bar ribs and the concrete teeth and the mechanical properties of the cohesive elements can work together to perform the bond-slip mechanism between the deformed bars and concrete.In the course of simulation, an integrated script program under the framework of Python language is introduced to execute the whole process of simulation including the random generation of aggregate, the assembly of matrix part and aggregate part, the definition of material properties, meshing, analysis step setting, finite element analysis and post- processing and has which can greatly improve the reproducibility of the test and work efficiency.