Automated Inspection of Rebar Spacing Based on Color Recognition of Painted Tie Wires

The quality of rebar construction is a critical factor that significantly affects the structural stability of reinforced concrete structures. Various automated inspection technologies have been developed to overcome the limitations of conventional labor-intensive inspection methods. However, owing to the complex geometry of rebar arrangements and challenging site conditions, existing approaches still face difficulties in achieving the high accuracy and real-time performance required for practical applications. To address these limitations, this study proposes an automated rebar-spacing inspection technique based on color recognition of painted tie wires with the aim of improving the efficiency and accuracy of data recognition and processing. Field experimental results demonstrated that the use of fluorescent-green tie wires in the HSV color space minimized false detections and achieved a high average recognition rate of 92.6% with the identification of optimal threshold ranges. Furthermore, by utilizing tie-wire intersection coordinates, the stable identification of rebar arrangement conditions and reliable estimation of rebar spacing were achieved, even under conditions with missing data. The proposed automated inspection method can enable more efficient data acquisition and processing under complex construction site conditions while providing accurate and reliable inspection results.