Multiscale Constitutive Model Development for Deteriorating Concrete

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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.