The Role of Special Inspections in the Safety Assessment of Bridges

Special inspection activities, as defined by the Guidelines for the classification and management of risk, safety assessment, and monitoring of existing bridges, play a strategic role in ensuring the safety of infrastructure assets. These inspections, carried out at variable intervals depending on the severity of deterioration and the attention class assigned to the structure fallowing routine surveillance activities, allow for a more in-depth and targeted evaluation of the condition of structural elements. In particular, the high level of detail required during the execution of these activities, combined with the use of specific diagnostic investigations on the most deteriorated portions, significantly contributes to improving the level of knowledge of the structures. This aspect is particularly relevant for bridges built using post-tensioned prestressing techniques, where degradation phenomena or hidden defects may not be detectable through simple visual inspections. This paper presents the results of inspection and diagnostic campaigns conducted on a set of motorway viaducts and overpasses, with the aim of highlighting operational characteristics, critical issues encountered, and the methodologies adopted. Furthermore, the impact of these activities on the assignment of the attention class and on the overall risk assessment of the examined structures is analyzed, offering reflections on the effectiveness of current regulatory and procedural tools in managing existing infrastructure assets.