Computational Modelling of Concrete Time-Dependent Mechanics and Its Application to Large-Scale Structure Analysis

The goal of the proposed work is to systematically study the time-dependent mechanics of concrete with a focus on concrete creep and its effect on prestressed concrete bridges, which are creep-sensitive. With increasing demands for sustainable construction, a longer lifespan, i.e., over 100 years, is now generally expected for critical bridges in structural design. To ensure the safety and serviceability of prestressed concrete bridges throughout this prolonged lifespan, there is a call for deeper understanding of the concrete time-dependent mechanics and its effects on the structural performance of prestressed concrete bridges. The primary aim of this study is to build a numerical framework to estimate the time-dependent performance of prestressed concrete bridges based on the development of concrete creep and its coupling with other physical and chemical processes. The established framework will be used to capture the correlation between the long-term asymptotes of deformation curves, early age measurements, and distinctive concrete creep models. Based on the identified correlation and in-situ measurements, a suitable creep model can be identified and calibrated for the bridge under investigation. Then the framework is extended to take into account the effect of scatter in concrete creep on the deformation asymptote. Statistical analyses based on the Latin hypercube sampling scheme are employed to investigate the effectiveness and robustness of the established correlation. For bridges carrying heavy traffic flows, the intertwined effects of concrete static creep, cyclic creep, softening and cracking are recommended to be incorporated to enhance the predictive capacity of the proposed framework. To meet this need, a unified concrete constitutive model is formulated and then is integrated in the 3D rate-type formulation for full-scale creep structural analysis. Finally, to remedy the inadequacy resulting from the phenomenological formulas in concrete creep modeling, a multi-scale methodology residing at the meso-scale of concrete is developed. A representative volume element (RVE) of concrete is numerically generated for the multi-scale analysis and the macros-scale time-dependent behavior of concrete is approximated by a proper computational homogenization scheme.