Multiscale Constitutive Model Development for Deteriorating Concrete

大多数民用基础设施都是用混凝土材料建造的。混凝土力学性能劣化是影响公共安全和经济性的重要问题。了解劣化混凝土的当前状态对于评估剩余能力至关重要。另一方面，了解现有结构的剩余容量对于决定改造，拆除或继续运营至关重要。混凝土材料在过度载荷下的老化劣化和/或失效通过裂纹发展而表现出来。在加拿大，冻融循环和潮湿环境中的碱-硅反应（ASR）是混凝土裂缝发展的主要原因。另一方面，由于地震或爆炸也可能发生过度载荷。在混凝土结构的使用寿命期间，可以基于计算机建模进行非破坏性测试和/或分析，以进行状态评估。无损检测，如图像处理，超声波设备和/或弹性波传播可以帮助识别裂纹配置。目前，在行业中存在对用于老化混凝土结构的剩余容量评估工具的显著需求。目前可用的工具提供有限的建模能力，当它涉及到评估现有的退化结构的剩余容量，因为安全系数和简化建议的准则在新结构的设计阶段不能被采用，以掩盖建模错误。根据现有条件预测结构的行为，以确定实际的失效情况是至关重要的。建议的研究旨在开发一个本构模型的混凝土材料考虑现有的裂缝配置，可以采用在结构分析失败。为此目的，拟议的研究旨在开发一个计算框架，它结合了混凝土材料的异质性，使裂缝的发展在细观尺度和不确定性的骨料和裂缝的分布可以考虑。建议的计算框架可用于结构的剩余能力分析，因此，它将提供一个全面和实用的基础上，以决定是否恢复连续运行，改造或拆除现有的混凝土结构。通过开发评估退化混凝土结构剩余能力的能力，拟议的研究解决了一个及时的需求，这是对识别现有裂缝的无损检测能力进步的补充。当对现有混凝土结构的健康和安全提出问题时，对剩余能力的准确评估将有助于在公共安全和经济之间进行明智的决策。

Majority of civil infrastructure is constructed using concrete material. For concrete, deterioration of mechanical properties is an important problem that effects the public safety and economy. Understanding the current state of deteriorated concrete is essential to evaluate the residual capacity. On the other and, understanding the residual capacity of an existing structure is essential when it comes to making decisions about retrofitting, demolishing or continuing with operations. Aging deterioration and/or failure of concrete material under excessive loads manifests itself by crack development. In Canada, freeze-thaw cycles and Alkali-Silica Reaction (ASR) in humid environment are major reasons of crack development in concrete. On the other hand, excessive loading may also occur due to earthquakes or explosions. During the service life of a concrete structures, it is possible to conduct non-destructive testing and/or analysis based on computer modelling for condition assessments purposes. Non-destructive testing such as image processing, ultra-sonic-devices and/or elastic wave propagation can help identify the crack configurations. There is currently a significant need in the industry for residual capacity evaluation tools for aging concrete structures. The currently available tools offer limited modelling capabilities when it comes to evaluating the residual capacity of an existing deteriorated structure because safety factors and simplifications proposed by the guidelines during the design stage of new structures cannot be adopted to cover up modelling errors. It is crucial to predict the structural behaviour based on its existing condition to identify realistic failure scenarios. The proposed research aims to develop a constitutive model for concrete material considering the existing crack configuration that can be adopted in structural analysis up to failure. For this purpose, the proposed research aims to develop a computational framework that incorporates the heterogenous nature of the concrete material such that crack development at the meso-scale and uncertainties in the distributions of the aggregate and cracks can be considered. The proposed computational framework can be used for residual capacity analysis of structures, and as such it will provide engineers a thorough and practical basis on which to decide whether to resume continual operation, retrofit or demolish an existing concrete structure. By developing capabilities to assess the residual capacity of deteriorated concrete structures, the proposed research addresses a timely need that is complementary to advancements in non-destructive testing capabilities that identify existing cracks. Accurate evaluation of the residual capacity will support a well-informed decision-making process between public safety and economy, when questions are raised regarding the health and safety of existing concrete structures.