Masonry bridge inspection using point cloud data and 360-degree images: a case study on railway bridges

In the context of the UK's aging infrastructure and reliance on railway masonry bridges, this study addresses the vital challenge of enhancing bridge longevity and safety through effective and accurate inspection methods. Traditional inspection techniques, while established, often disrupt service, pose safety risks, and incur high costs. In contrast, digital inspection techniques, such as 360-degree imagery and point cloud data, offer increased efficiency and minimal disruption. However, these methods have not been extensively tested in real-world settings beyond the experimental conditions. Addressing this gap, our research aims to evaluate the effectiveness of these digital techniques against conventional inspections across four masonry bridges. By replicating existing examination results with digital datasets, this study explores the potential of the integration of a digital examination approach into the UK railway bridge inspection protocols, engaging industry experts to assess the applicability of broader adoption. Employing an exploratory case study methodology, the research collected and analysed data to ascertain digital detection rates for various structural defects. Findings indicate a 46% detection rate using digital methods, with joint defects and spalling achieving over 85% success when excluding repaired and tactile-related defects. However, challenges in detecting cracks, fractures, and bulging were evident, primarily due to image quality issues and physical obstructions. Proposed corrective strategies, such as improved data capture techniques and more precise specifications, suggest potential advancements in detection rates. Nevertheless, the absence of a correlation between defect severity and detection rates underscores the limitations of digital methods, particularly for defects requiring tactile examination. Despite these challenges, discussions with industry experts supported the operational viability of digital examination methods, highlighting anticipated benefits in safety, efficiency, and decision-making, thus suggesting their suitability for widespread application. This study not only advocates for the integration of digital inspection techniques into existing protocols but also underscores the necessity for further research to refine these methods for practical use.