Comparison Analysis of Free Shrinkage Strains of Reinforced Concrete Box Girder Bridges Repaired With Concrete Overlays Academic Article in Scopus uri icon

abstract

  • When damaged bridges are repaired with new concrete overlays, the interface between new and old concrete restraints the high shrinkage of the overlay, leading to the development of tension stresses in the overlay, compression and bending stresses in the substrate, and shear stresses across the interface [1]. These stresses lead to cracks, through which corrosion and unbonding of the steel reinforcement is induced, and consequently cause failure of the repairs and compromise the static and dynamic performance of the repaired infrastructure [2]. In this study a numerical model was developed to predict the development of free shrinkage strains of reinforced concrete box girders repaired with overlays of different thickness and concrete compressive strengths to estimate the magnitude of the involved restrained stresses. The influence of the variability of the environmental humidity is also explored. Results show that for a typical 250 mm- thick overlay with concrete compressive of 30 MPa, and environmental humidity equal to 0.5, the maximum free shrinkage strain in the overlay after three years is estimated to be 529 ¿¿, which corresponds to 78% of the ultimate free shrinkage strain, ¿sh¿. Over the same time frame, increasing the environmental humidity to 0.75 gives maximum shrinkage strains of 68% ¿sh¿. Similarly, decreasing the thickness of the overlay to 150 mm leads to the development of free shrinkage strains of magnitude about 81% ¿sh¿ after three years. Finally, considering an Ultra High Performance Concrete overlay generates slightly smaller maximum strains than regular concrete: the predicted value of the maximum free shrinkage strain for the overlay is around 71% ¿sh¿. Although these findings may be limited by the chosen geometry, they generally show that changes in the environmental factors and material properties affect the maximum free shrinkage strain. Particularly, a more humid external environment, a higher strength concrete and a thicker overlay reduce the susceptibility to cracking of the overlay with respect to the baseline case study. © 2024, World Congress on Civil, Structural, and Environmental Engineering. All rights reserved.

publication date

  • January 1, 2024