Bridge Inspection and Investigation

We offer consultation and in-depth post-tensioned concrete bridge special inspections (PTSI). During our condition investigations, we’ll examine every detail while always avoiding needlessly intrusive examinations.

Post-tensioning for concrete structures can range from clearly threaded bars to intricate multi-strand arrangements in beams, crossheads, decks and piers. Particularly difficult features include segmental constructions or tensioning at unreachable locations. Infamous failures at Ynys-y-Gwas (1985) and more recently in Genoa (2018) have showcased how vulnerable post-tensioned bridges are to hidden defects. Ongoing investigations and monitoring schemes are vital to avoid any repeat incidents. However, DMRB DB54/15 requires all post-tensioned concrete structures to be managed on a risk basis, with investigations carried out where necessary.

We offer specialised condition investigation services for bridges with reinforced concrete half-joints. From the first consultation through to risk review and testing, we can find out the risk of serious defects, and offer advice on the structure’s performance.

Half-joints in reinforced concrete bridge decks and sub-structures can be found in all sorts of forms, which are typically found in areas that are difficult to access, as well as pose the risk of hidden defects. Water leakage through the movement join is typically the cause of common defects, as any corrosion causes could go undetected. While visual inspections can find any external issues, they’re typically insufficient to confirm the internal condition.

With bridge collapses in Canada and Italy taking place in the last few years, and both involved hidden defects in reinforced concrete half joins – where visual inspection alone wasn’t enough to see the severity of the condition prior to collapse.

Our complete and comprehensive service are relevant to each situation. Our non-destructive techniques are used to investigate internal corrosion and cracking. We’re also able to keep track of any movements and create a warning system to keep you aware of further deterioration. We can also provide:

• Review of available drawings, inspections and past investigations
• Special visual inspections
• Risk scoring and prioritisation
• Radar and eddy current scanning to determine internal reinforcement details, checking bar positioning and anchorage lengths
• Concrete condition investigations for external faces, including carbonation, chlorination and half-cell potential
• Ultrasonic screening through concrete for detection of internal cracking at mid-depth
• Structural monitoring for future condition changes and damage detection
• Interpretive review and recommendations for bridge management

Our inspection and monitoring techniques are ideal for spotting fatigue in metallic structures. As well as this, we can monitor any strains to predict future fatigue.

By measuring crack development, stress cycles and counting fatigue damage accumulation, we can remotely monitor any progression, and suggest appropriate times for intervention.

Localised stress and heat affected zones of welded components are often the cause of fatigue related cracks developing in steel bridges. Visual inspection isn’t enough to find the minute cracking, which often begins in areas not easily accessed, like steel decks or box girders. This can make early detection almost impossible.

Magnetic Particle Inspection (MPI) is usually used in traditional testing programmes, where they are applied to a section of weld details suspected at higher risk. We can provide alternative techniques for defect detection that are safer, quicker and better for the environment by working to avoid surface preparation and related hazards. What’s more, some techniques can even be carried out remotely.

As part of our fatigue detection in metallic structures services, we can provide:

• Review of available drawings, to comment on stress concentration prone details and fatigue risk
• Strain monitoring
• Fatigue damage calculation and graphical display on SAMS™
• Weld visual inspections for construction quality
• Eddy current testing verified locally by MPI or dye penetration
• ACFM for comprehensive investigation and crack depth measurement, without paint removal
• Robotic corrosion mapping
• Phased array ultrasonic weld inspection

Vehicle collisions to bridges can cause extended disruptions and a risk to public safety. In these situations, swift responses are needed to make sure safety is maintained, and there is minimal disruption to the road. Floating debris in floods can be just as damaging and need similar attention.

For concrete bridges, just some of the services that can be used include hammer tap surveys or ultrasonic investigation to map cracks. When it comes to steel or iron structures, we suggest ACFM (alternating current field measurement). This is where eddy currents are used to measure the extent and depth of cracks without removing paint. Many other techniques are also available, which can be catered to each specific condition.

We also have a suite of monitoring solutions, known as BridgeStrike. This service is used to check the bridge deck in real time for any sudden impacts. Our cameras can even capture images of the vehicle before, during and after impact, which not only helps with bridge management but can also lead to perpetrator prosecution.

Just some of the other monitoring solutions we provide include can detect over-height, over-width and/or over-weight vehicles. This then activates warning signs, which can pre-empt action and avoid impact. What’s more, we can even detect flying over-height aerials which could come into contact with electrified railway overhead line equipment (OLE).

Other services available:

• Review of previous impact damage and testing conducted
• Emergency visual inspections
• Dimension surveys for assessment
• Broad range of non-destructive testing including ultrasonic and ACFM
• Review of impact severity and recommendations
• BridgeStrike monitoring for impact records and imagery
• Impact magnitude recording for future enhanced response
• Over-height, over-width and over-weight vehicle detection to activate warning signs

Over-height, over-width, and over-weight vehicle detection to activate warning signs

Due to recent high profile failures, new guidance has been released that calls for a review of fixings that are relied upon. As part of our service, we can offer a complete review of the condition of critical fixings within assets.

Ciria guidance, ‘Management of Safety Critical Fixings C778’, states that bolts used for safety or that pose a risk to operation must be reviewed. Such fixings include claddings, parapet bolts, structural connections, suspended ceilings, lighting and signs. With our team’s experience and suite of non-destructive testing services, we can find out and categorise risk features.

Often features are installed on a ‘fix and forget’ basis, leaving behind no record of installation details. Rest assured; we have this covered. Our experts will investigate the available information, and combine measurements, testing, and inspection to suggest the details most likely to evaluate risks.

Other services include:

• Review of structural details and known information
• Load testing and certification
• Detailed visual inspection
• Bolt scanning by phased array ultrasonic testing to find corrosion and necking even when hidden inside concrete
• Listing and categorisation of all known safety critical fixings
• Risk rating and recommendations for management programme

The hollow sections and fastening bolts of bridge parapets are the usual places where deterioration can occur. This is because after installation, they typically receive little to no maintenance. In these circumstances, visual inspection is insufficient to find out the integrity of these hidden features.

We combine our services to provide a complete, end to end service for investigation into the condition of bridge parapets and highway safety fences.

We recommend cursory checks using non-destructive tests at a sample of locations at regular intervals. If deterioration is found, more thorough investigative programmes can be provided. What’s more, we can also advise on the most suitable testing services.

In the past, vehicles have often collided with parapets while attempting to access bridges that have height or width restrictions. Any undetected defects caused by these collisions can lead to bridge parapets not meeting the rated resistance they should. You can find out more about the proper management of parapets, which includes risk ranking and prioritising upgrades, from Highways England.

With our specialist team, we can provide:

• Collating and review of record information
• Visual inspection
• Ultrasonic thickness measurements for posts and rails – for which we suggest B-scans to establish both minimum and average thickness
• Bolt scanning by phased array ultrasonic testing
• Weld inspection and testing
• Bolt load testing and certification
• Paint inspection and testing
• Inspection and measurements at zones of impact and use of ACFM technique for damage measurements
• Physical load testing of barrier system (static or dynamic)
• Monitoring for changes in condition or safety fence tension
• Since parapet resistance is reliant on the supporting structural plinth, we can extend investigations into the steel or concrete components around
• Risk rating and recommendations for management programme