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

本研究分为两个阶段。第一阶段以塑性理论为基础，建立了混凝土的本构模型。在第二阶段中，结合所提出的本构模型，在有限元程序中模拟了受载混凝土的行为。本文的研究成果总结如下：1.提出了混凝土的广义本构模型。该模型既能反映混凝土在应力下降范围内的多轴性能，也能反映混凝土在应力上升范围内的多轴性能。2.该模型考虑了混凝土破坏过程中的塑性功消耗，间接考虑了混凝土的细观机理。3.在有限元程序中引入了广义本构模型，成功地模拟了受压约束混凝土柱的受力性能。本文通过数值模拟，讨论了该程序对以下几个方面的预测能力：1)混凝土轴压破坏行为；2)约束混凝土轴压破坏行为；3)试件尺寸或有限元的影响；4)内部缺陷的影响；5)出血对强度分布的影响；5)预测受压约束混凝土的破坏或应变软化行为。6.为了缩短计算时间，需要对以下几个方面进行进一步的研究：1)建立快速回弹行为模拟的计算方法；它在目前的有限元程序中没有被成功地编码。

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.