混凝土宏细观PD状态建模与损伤破坏过程全时域仿真

The accurate description and numerical simulation for the damage and failure mechanism of concrete materials and structures is one of the key issues in structural safety and high-performance concrete studies. In this proposed research, the recently developed non-ordinary state-based peridynamics theory will be employed to describe the heterogeneous long-range and short-range interactive actions between material points of aggregates and mortar based on theoretical analysis and experimental observations, taking the multi-phase nature and cross-phase interfaces at meso-scale as well as the mechanical behavior of concrete at macro-scale into account, and correlating the parameters in the state-based peridynamic constitutive models with the key characterizing meso-scopic material constants. ..An extended multi-scale state-based peridynamic approach will be proposed to simulate the continuous and discontinuous problems with the identical non-local integral-typed model and corresponding numerical algorithms. The proposed numerical system will be validated through analytical solutions and experimental observations, and then it will be used to analyze the quantitative deformation as well as the whole damage accumulation and failure process of concrete materials and structures, including the damage localization, crack emergence and propagation along the interfaces between aggregates and mortar, and macro cracking...The failure mode and failure mechanism of concrete materials and structures in various static, dynamic and complicated loading cases will be investigated and concluded through numerical analysis using the proposed multi-scaled peridynamic approach, and the effect of inner meso-structures of materials on the macroscopic mechanical behavior, damage accumulation and progressive failure mechanism of concrete will be analyzed in depth. It will shed new light on the development of high-performance concrete as well as the safety evaluation of concrete structures, and will potentially provide a promising alternative way for analyzing complicated discontinuous problems and for modeling the mechanical behavior of similar heterogeneous and anisotropic composite materials.

混凝土的损伤破坏机制对结构安全评估与发展高性能混凝土很重要。项目基于新的近场动力学（Peridynamics，PD）状态思想，构建既考虑混凝土细观非均质、多相特征以及同/异相组分间的长、短程作用和界面效应，又能反映其宏观力学特性的宏细观非局部PD状态本构模型，分析PD本构模型参数与非均质材料细观结构特征参数之间的内在联系；开发能以统一的非局部空间积分-时间微分型力学模型和算法分析连续-不连续问题的时空多尺度PD数值体系，实现混凝土材料和结构定量变形计算以及细观分布式缺陷发展、损伤累积与局部化、宏观裂纹萌生/扩展乃至整体失效全过程的连续仿真；结合分组静、动力及复杂加载状态混凝土材料和结构破坏过程多尺度全时域仿真与宏细观实验，分析混凝土宏观力学特性与破坏的内在机制，为混凝土结构安全评估和高性能混凝土研发提供科学依据，并为类似的非均质、多相复合材料的本构建模及复杂不连续力学问题分析提供新思路。

混凝土是建筑工程等领域中最广泛使用的典型的非均质不连续多相复合材料。混凝土材料和结构的损伤破坏是涉及跨尺度的强不连续力学问题，其破坏的物理机制及破坏过程的高效数值模拟一直是多领域关注的热点和难点。本项目主要基于非局部态型近场动力学（Peridynamics，PD）思想，构建了能准确、高效地描述混凝土材料和结构力学行为及其在包括热-力耦合、流-固耦合、冲击侵彻等外部因素作用下损伤破坏全过程的多尺度PD模型和算法体系，并通过典型加载工况模拟，研究了混凝土材料和结构损伤破坏的内在机制。. 项目构建了既考虑混凝土细观结构特征，又能反映其宏观力学行为的非局部宏细观态型PD本构模型，以及适合于分析混凝土类材料和结构热传导、热力耦合变形破坏问题的PD模型与算法。基于态型PD理论框架构建了混凝土水力压裂分析模型，从裂隙岩体流动特性分析入手，建立基于态型PD的裂隙流固耦合模型，对不同模型在处理水力压裂问题上的优势和不足进行了对比验证，并应用所提出的模型对二维、三维水力压裂问题进行研究，对工程中裂缝扩展的关键影响因素进行了系统的分析和讨论。考虑率效应和动力损伤的影响，将传统应变率与PD模型中键的伸长率联系起来，构建新的考虑率效应的态型PD混凝土模型，并应用于混凝土结构的动力破坏模拟。在此基础上，进一步将混凝土HJC模型等在PD理论框架中实现重构，考虑混凝土在大应变、高应变率和高围压条件下的损伤破坏特征，实现复杂条件下混凝土结构的冲击破坏模拟。. 项目研究成果为混凝土构件及混凝土结构的安全评估与寿命预测提供了可望替代部分现场测试的新方法，为混凝土性能的改善以及新型高性能混凝土的研发提供科学依据，对类似的岩石类材料及其他非均质多相复合材料的力学特性与破坏机制研究也具有重要意义，还可为构建新型多尺度非局部本构模型与数值算法、模拟复杂强不连续力学问题以及土木、水利和国防等工程中的结构设计优化与健康监测提供参考。