Serviceability estimation of reinforced concrete beams focusing on crack propagation and deflection

Experimental and parametric studies were conducted to examine the relationship between crack propagation and deflection in reinforced concrete beams with varying reinforcement ratios and concrete covers. Four-point loading tests were performed, and deflection and crack width were measured using both digital image correlation (DIC) and traditional methods. While the DIC method accurately tracked deflection and individual crack propagation, it overestimated total crack width due to the inclusion of elastic strains. A linear correlation between total crack width and flexural deflection was observed in the experimental data. A model was developed to estimate deflection based on crack widths measured by DIC, incorporating elastic strain and assuming idealized curvature-based flexural deflection and shear deformation. The model predicted deflection with a maximum error of 6.90%, simplifying serviceability estimation. A parametric study using finite element analysis (FEA) on 30 beams showed that shear span significantly influences load capacity. As the concrete cover thickness and the distance from the loading point increased, the width of the cracks also increased. The proposed model effectively predicted the crack-deflection relationship, showing a maximum error of 5.50% compared to simulations.