The structural performance of reinforced concrete (RC) members affected by alkali–silica reaction (ASR) is difficult to predict because of the multi-scale phenomena. Recent structural tests reveal that the performance of RC members also depends on ASR-induced crack patterns, including localized cracks and dispersed microcracks. Additionally, microscopic factors, such as crack-filling by gel and presence of microcracks, are relevant. To explore this in detail, a computational system for finite element analysis of ASR-damaged RC members was developed. This study numerically investigated the structural behavior of ASR-affected RC members based on localized/dispersed crack patterns and microscopic factors. The applicability of the developed computational system was verified by comparing the analysis results with experimental data. The analysis results showed that ASR-damaged RC members with dispersed microcracks exhibited highly ductile behavior, while those with localized cracks failed in shear. This is because the dispersed crack pattern prevents the shear crack propagation and enhances the mechanical contribution of gel filling cracks, while the localized ASR cracks facilitate critical crack propagation, leading to failure, and minimize the gel-filling effect. Through the analytical investigations, it was found that the localized ASR cracks can result in significant loss of structural performance; thus, this study recommends the assessment of structural capacity of RC members in the case where the localized cracks were observed.

Tunnels that cross fault crush zones are subject to local deformation along these zones during earthquakes. Because the tunnel axis and the fault plane generally intersect in a three-dimensional manner, evaluating structural performance by using three-dimensional FEM is reasonable, and to this end selection of an appropriate damage indicator is required. To establish a damage evaluation method for the safety of tunnels subjected to local deformation, three-dimensional FEM analysis was carried out on previous loading experiments, the failure modes were analyzed, and the applicability of several damage evaluation indicators was verified. As a result, the damage to the tunnel in the model experiments was broadly classified into in-plane shear in the longitudinal section and out-of-plane shear in the longitudinal or transverse section. Performance evaluation using compressive damage indicators including minimum principal strain when the limit state of a tunnel is defined as the point at which the resistance to slippage in the crush zone is maximum was found to be feasible. Moreover, the results of the sensitivity analysis showed that evaluation based on the minimum principal strain is broadly applicable. Additionally, a limit value considering element size was proposed.

Mechanical stress can promote dissolution of calcium hydroxide in concrete; combined with carbonation, this may accelerate creep, damage, and corrosion. The existing microstructural simulators struggle with stress-induced dissolution processes, because of their strong chemo-mechanical coupling. This article presents results from recent Kinetic Monte Carlo simulations of dissolution and precipitation of solid phases, described as mechanically interacting particles. Chemo-mechanical coupling is embedded in the chemical reaction rates, featuring both chemical potentials of ions in solution and mechanical stress in the solid. The simulations are applied to a calcium hydroxide crystal, at chemical equilibrium in a solution of its ions but compressed between two stiff platens. Depending on the applied stress, the crystal partially dissolves and recrystallizes, producing an apparent viscoplastic deformation process. The simulation results inform mathematical creep laws with a size effect, as the strain rate depends on the crystal size. Upper-bound creep moduli for typical calcium hydroxide crystals in concrete are estimated as 237 to 2370 GPa, and carbonation would likely reduce them. This indicates that stress-induced dissolution of calcium hydroxide may underpin the nonlinear acceleration of concrete creep during carbonation. An experimental strategy to assess this mechanism is finally proposed, leveraging the size effect argument.