Concerns about damaged and deteriorating bridges and the harm that they could cause to the people who cross them and their surrounding communities are top of mind for everyone working in the bridge industry today. Inadequate government funding to maintain the nation’s bridges and roads has left many in dangerous conditions.

This has forced more frequent — and in-depth — inspections of bridges and roads across the United States. Here are the most common tactics and techniques being used by inspectors today, along with the pros and cons — and bottom-line benefits — of each.

Visual inspection.

This is the most common type of inspection. It simply involves looking over the structure with the naked eye or using tools, like bridge lifts or drones with cameras, to safely bring hard-to-access areas within view. People doing visual inspections can detect damage like potholes, cracks, spalling, and certain types of corrosion. Visual inspections make it possible to handle these issues as they happen and to take steps to see if they’re signs of deeper and more serious problems.

Pros: A visual inspection is an easy, straightforward, and cost-effective way to look out for damage on bridge surfaces. It doesn’t require special training and can take place on an ongoing basis.

Cons: While a good starting point for seeking out bridge damage, a visual inspection doesn’t allow for an adequate assessment of what’s happening on the interior of the structure or the sections under the bridge.

The bottom line: A visual inspection is the first line of defense when it comes to protecting bridges against significant damage. It should be at the center of every bridge inspection program. 

Tip: Leveraging the right equipment, like the innovative lifts from BridgeMasters, can make it easier to conduct visual inspections of bridges, making hard-to-access areas easy to reach.

Acoustical inspection.

This relatively simple technique is performed by dragging a chain or tapping a hammer on the surface of a bridge while listening for changes in sound pitch. An experienced professional can use this type of test to detect delamination, coating separation, and whether the structure could be splitting into layers.

Pros: This is a simple and easy tactic that can be leveraged at any time. It can be used as an initial test when certain types of structural damage are suspected.

Cons: This type of relatively simplistic test may not be completely accurate, especially because people hear things in different ways. Also, bridges with asphalt overlays can’t be tested this way.

The bottom line: Much like visual inspections, acoustical ones can provide value when damage is suspected and inspectors want to learn more. However, they should never be used to make final decisions about whether a bridge is compromised.

Infrared or thermal imaging inspection.

This type of testing goes beyond surface- or sound-level inspections by seeking out changes in infrared radiation or temperature levels, which could indicate structural changes and other issues.

Pros: If structural issues are suspected, this kind of testing can be performed quickly and easily by experienced professionals. They are highly likely to produce meaningful and actionable results.

Cons: Infrared or thermal imaging inspections can’t be performed on bridges with asphalt overlays. Also, data is only valid on thermal inspections if there is a significant temperature difference between the bridge and the environment around it.

The bottom line: These types of inspections can provide great value in the right circumstances. They should be a part of every inspector’s tool kit.

Coring and chipping.

At its simplest, this tactic involves drilling holes into the surface of a bridge to learn about the condition of the steel reinforcement, access corrosion damage, and look into the physical and chemical properties of the concrete elements. Any level of deterioration — or unexpected results — could indicate a significant structural problem.

Pros: Much intel about the health of the concrete and the associated steel reinforcement of a structure can be gained using this method.

Cons: This technique can cause damage to a bridge that could impact its overall structural integrity. 

Bottom line: Once data has been collected, the holes must be repaired. Otherwise, more harm could be done to a bridge beyond the original damage that was being inspected.

Ground-penetrating radar (GPR) inspection.

This type of testing uses electromagnetic radiation to look below the concrete surfaces of bridges to detect issues like delamination, voids, and cracks.

Pros: A GRP inspection provides highly reliable and completely objective quantitative data related to the health of concrete structures. The data generated by this type of testing isn’t subject to human perceptions or biases, which is often the case with visual- or sound-related inspections.

Cons: GPR testing requires experienced professionals to conduct the inspections and interpret the data. They’re also notorious for consuming a great deal of energy.

The bottom line: If you suspect that there’s an issue with a bridge, leveraging GPR inspections is a good way to find out for sure if there’s damage below its surface. 

Half-cell potential inspection.

This non-invasive testing method checks the voltage between the steel reinforcement within the concrete and an electrode that is placed on the concrete surface in order to monitor corrosion levels.

Pros: This inspection method can detect corrosion in its early stages, so it can be taken care of before it becomes genuinely destructive. It’s also possible to get a reading on the steel components without being in direct contact with them. This type of test is relatively quick and in many cases, can be completed in under a minute. 

Cons: This method of testing can be more costly than other ones. The results will be better if it’s conducted by experts, even though using the measuring device is relatively easy.

The bottom line: While half-cell inspections can be somewhat costly, conducting them regularly could help you identify small corrosion issues long before they become big problems.