Development of Generalized Finite Element Model for Compressive Concrete Based on Micro-Mechanism

本研究分为两个阶段。在第一阶段，提出了一个混凝土本构模型，塑性理论的基础上。在第二阶段中，加载混凝土的行为进行了模拟的有限元程序，将建议的本构模型。主要研究成果如下：1.建立了混凝土广义本构模型。该模型不仅能反映混凝土在应力下降段的多轴受力性能，而且能反映混凝土在应力上升段的多轴受力性能; 2.该模型以混凝土破坏过程中所消耗的塑性功为主要参数，间接地考虑了混凝土的细观破坏机理; 3.该有限元程序能较好地模拟约束混凝土受压柱的受力性能，其中对所提出的广义本构模型进行了详细的说明.在本研究中，通过数值模拟，讨论了该程序对以下问题的预测能力：1）混凝土轴压破坏行为2）约束混凝土轴压破坏行为3）试件尺寸或有限元尺寸的影响4）内部缺陷的影响5）5.计算结果表明，所编制的程序对预测材料的破坏或应变是十分有用的。约束混凝土受压软化行为的研究6.需要进一步研究的问题有：1）缩短计算时间; 2）建立回弹行为模拟的计算方法，这在目前的有限元程序中没有成功地编码。

There are two stages in this study. In the first stage, a constitutive model for concrete was proposed, based on the plasticity theory. In the second stage, the behavior of loaded concrete was simulated in the finite element program, incorporating the proposed constitutive model. Results in the present study are summarized as follows :1.A generalized constitutive model for concrete was successfully proposed. The model can represent the multi-axial behavior of concrete in the stress descending range as well as in the ascending range.2.In the proposed model, the plastic work consumed in concrete during the failure process is incorporated as a main parameter, which means that the micro-mechanism of concrete is indirectly considered.3.The behavior of compressive confined concrete columns can be successfully simulated in the finite element program, in which the proposed generalized constitutive model is incorporated.4. In the present study, simulation was carried out to discuss the capability of the program in the prediction for the following items.1) Failure behavior of concrete under axial compression2) Failure behavior of confined concrete under axial compression3) Effect of size of specimen or finite element4) Effect of inner defect5) Effect of strength distribution due to bleeding5.It is demonstrated that the coded program is quite useful to predict the failure or strain-softening behavior of confined concrete under compression.6.Further research is needed for the following items.1) To shorten the time for calculation.2) To establish the calculation method for the simulation of snapback behavior, which was not successfully coded in the present finite element program.