Inspection of engineering structures: nearly 30% of municipal bridges reveal alarming structural problems

Delaying the work results in a direct cost multiplied by three**, as well as socio-economic impacts up to six times higher**, particularly due to traffic disruptions.

In this context, the inspection of engineering structures appears as an essential lever to anticipate risks, ensure the safety of users and guarantee true asset optimization.

To address these challenges, engineering firms specializing in the inspection and maintenance of engineering structures, such as BOAS, support local authorities and managers throughout the territory.

What are the objectives of the inspection of engineering structures?

Engineering structures are essential components for the operation of transportation networks, whether they are road bridges, railway structures, or pedestrian bridges. The primary objective of their inspection is to prevent major human and economic risks associated with structural failure. Beyond this safety imperative, the inspection also aims to:

• Preserve existing heritage by limiting the progressive deterioration of materials (concrete, steel, masonry);
• Optimize budget management through rational and multi-year planning of interventions;
• Ensure compliance with applicable technical and regulatory standards.

Monitoring thus constitutes the first link in the safeguarding chain, transforming a technical constraint into a real decision-making tool for infrastructure managers.

How often should engineering structures be inspected?

The frequency of inspections is a key factor in asset management. Generally, a detailed periodic inspection should take place every six years, supplemented by shorter annual visits. This schedule allows for monitoring the progression of deterioration and planning a coherent long-term maintenance program.

Proactive management helps to avoid tonnage restrictions or road closures that heavily impact the local economy.

What are the common pathologies of engineering structures?

Engineering structures are exposed to the “natural” aging of materials, but also to multiple forms of aggression: pollution, de-icing salts, humidity, and heavy loads. Among the most frequent structural problems are:

• Concrete cracks: whether due to shrinkage, bending or shear stress.
• Corrosion of reinforcement: an often invisible phenomenon that can compromise the load-bearing capacity of reinforced or prestressed concrete.
• Damage related to freeze/thaw cycles: causing concrete to spall.
• Disorders affecting supports: such as the aging of elastomer support devices.

Identifying these signs at an early stage allows for a removal of doubt quick on the stability of the structure and avoids heavy and costly repairs.

How is an inspection of engineering structures carried out?

To ensure reliable and consistent monitoring, engineering missions rely on the methodological framework defined by the Technical Instruction for the Monitoring and Maintenance of Engineering Structures (ITSEOA).

The interventions are also structured based on the Maintenance Engineering Reference Framework, developed by IMGC, a leading association dedicated to the maintenance of civil engineering structures.

Periodic detailed inspection

The periodic detailed inspection consists of a comprehensive visit to all parts of the structure (deck, supports, equipment), with the implementation, if necessary, of appropriate access methods. It includes:

• a comprehensive inventory of the damage, accompanied by a detailed photographic report;
• the creation of a map of the disorders on a scale;
• the drafting of a detailed report including an opinion on the structural condition and recommendations for work.

The evaluation visit

The evaluation visit allows for monitoring the structure's condition between two major inspections. It is based on a rigorous visual examination and results in a summary report, essential for defining any necessary changes and routine maintenance measures.

Legal liability in case of failure to inspect

Beyond the technical aspects, the inspection of engineering structures provides protection for the manager. In the event of an incident, the owner may be held liable for failure to properly maintain the public structure if a deficiency in oversight is demonstrated. Having up-to-date inspection reports thus provides evidence of diligence and sound management of public or private assets.

To guarantee reliable and actionable analyses, it is essential to entrust these tasks to an experienced professional. BOAS's teams offer comprehensive expertise in the inspection of engineering structures, from initial assessment to support in defining and monitoring work programs, thus contributing to the sustainability and safety of infrastructure.

Sources: *Cerema – National Bridges Programme (2025); **STRRES – Bridge Repair Contractors × CITIZING Consulting (2025)