强动载荷下混凝土新的3D细观力学模型研究

Concrete as construction material has been widely used in both defense and civil engineering. An understanding of the response and failure of concrete subjected to intense dynamic loadings such as high speed penetration and explosion is of great significance for the design and assessment of weapons as well as protective structures. The purpose of this project is to build a new 3D meso-mechanical model for concrete and to formulate a dynamic constitutive model which not only takes into account the effects of various parameters but also is easy to be implemented into computer software.The main contents of the present research proposal are as follows: (1) to propose a 3D two-phase meso-mechanical model with different aggregate shapes by virtue of basic aggregate growing outward randomly; (2) to construct ITZ elements between aggregates and cement mortar to generate a new 3D three-phase meso-mechanical model by elements reconstuction method based on the proposed two-phase model; (3) to formulate a dynamic constitutive model by taking into account various factors; (4) to study the capacity of resistance to penetration and explosion as well as failure morphology by means of the new meso-mechanical model and constitutive relations; (5) to validate the meso-mechanical model and constitutive model against experiments.

混凝土作为一种建筑材料在国防和土木工程中得到了广泛的应用，研究混凝土在强动载荷下（如高速侵彻或爆炸）的响应和破坏问题对武器、防护结构的设计和评估具有重要意义。本项目拟建立混凝土新的3D细观力学模型和构建一个不仅考虑各种因素的影响而且方便计算应用的混凝土动态本构模型来研究混凝土在冲击载荷下的响应和破坏。主要研究内容如下：（1）利用基骨料向外随机延拓的方法生成骨料形状不同的3D两相混凝土细观力学模型；（2）在两相模型的基础上利用单元重构的方法在骨料和基体之间创建ITZ层单元获得3D三相混凝土细观力学模型；（3）建立考虑各种因素的混凝土本构模型；（4）利用新建的细观力学模型和本构关系研究混凝土抗侵彻和抗爆炸能力以及破坏形貌；（5）通过实验验证细观力学模型和本构模型的正确性。

混凝土作为一种建筑材料在国防和土木工程中得到了广泛的应用，研究混凝土在强动载荷下（如冲击或爆炸）的响应和破坏问题对武器、防护结构的设计和评估具有重要意义。本项目建立了混凝土新的3D细观力学模型并构建了考虑各种因素的影响的混凝土动态计算本构模型来研究混凝土在强动载荷下的响应和破坏。主要创新性研究成果如下：.(1) 建立了混凝土新的3D细观力学模型。其中骨料分为球形骨料或不规则(凸多面体)骨料，利用单元重构技术和3D壳单元构建界面过渡区（ITZ层）；.(2) 构建了混凝土动态计算本构模型。该模型主要包括孔隙状态方程和强度面，考虑了压力相关性、剪切和拉伸损伤、Lode角效应、应变率效应和自由水效应等主要因素；.(3) 利用研发的混凝土新的3D细观力学模型和开发的混凝土动态计算本构模型数值模拟了相关混凝土结构冲击实验。结果表明：数值模拟得到的结果和实验观察吻合得较好。.(4) 首次设计并进行了钢筋混凝土结构的尺度效应抗爆实验。试件选择梁、板、柱三种，每种三个尺寸，严格按照1:2:3的尺度比例（包括结构、骨料和钢筋尺寸）进行缩放设计。并利用所开发的混凝土动态计算本构模型数值模拟了对应混凝土爆炸实验。.实验结果表明：在实验参数范围内，钢筋混凝土结构在爆炸载荷作用下的响应和破坏有一定的尺度效应，大尺寸试件破坏较小尺寸严重；数值模拟结果表明：利用所开发的混凝土动态计算本构模型模拟所得的结果与实验观察吻合得很好，且能预测钢筋混凝土结构在爆炸载荷作用下所观察到的尺度效应，从而进一步验证了模型的准确性。