Experiment-based characterization of spatiotemporal random fields for steel corrosion in RC structures

This is the authors' abstract. We don't add key points for this paper.

The spatial and temporal variability of corrosion affects the time-dependent performance of aging reinforced concrete (RC) members because the correlation structure influences the extent to which deterioration develops simultaneously across multiple reinforcing bars. Previous studies have simulated steel weight loss by incorporating anisotropic spatial correlation in the longitudinal and transverse directions. However, the evolution of spatial corrosion patterns over time, referred to here as spatiotemporal correlation, has received limited attention in simulations and experiments. This paper develops a three-dimensional univariate random field for time-dependent steel corrosion that accounts for correlation along and among multiple tensile rebars and over the investigated exposure period. The model combines the spectral representation method with a frequency-wavenumber spectrum to generate realizations with prescribed anisotropic spatiotemporal correlation. A procedure is proposed to estimate the model parameters through Fourier-transform analysis of time-sequenced steel weight loss data. The procedure is applied to data obtained from two RC slab specimens subjected to controlled wetting-drying cycles and measured at multiple times using X-ray imaging and digital image processing. As an illustrative example, the developed random field is applied to corroded RC slabs. The calibrated parameters are interpreted primarily within the experimental observation period, while results beyond the final inspection are treated only as a short illustrative extrapolation. The results show that the calibrated spatial and temporal correlations affect the persistence of localized corrosion patterns and the distribution of the minimum total residual cross-sectional area of multiple tensile rebars.