An Analysis of Modern Bridge Inspection Technologies
It's no secret that America's bridges aren't the most durable. According to the American Society of Civil Engineers (ASCE), a shocking 25% of bridges across the United States are structurally deficient or functionally obsolete. Shockingly, many of them are still in use.
In addition, the average age of the nation's bridges is 42 years; meanwhile some are as old as 80 years! In order to ensure the safety of Americans using these infrastructures every day, we need to not only increase the frequency of bridge inspections but also to use the best tools and technology available today.
An Overview of Destructive and Non-Destructive Methods of Inspecting Bridges
Below is a list of key bridge inspection techniques, from destructive methods such as coring and chipping to non-destructive testing.
Used to detect delamination, the separation of coating or the splitting of a structure into layers. This test is non-destructive and is performed using a chain drag or hammer to identify the changes in sound pitch. The advantage to this method is the lack of training needed to perform the tests and the low costs of equipment. On the other hand, not all tests may be accurate due to hearing biases and cannot be tested on bridges with asphalt overlays.
Infrared/Thermal Imaging Inspection
This method looks into changes in infrared radiation to indicate delamination from the surface of concrete. Once again, this method cannot be performed on bridges with asphalt overlays, however, it can be performed quickly in a moving vehicle, thus minimizing bridge downtime. On the other hand, the data must be obtained when there is a large thermal gradient between the bridge and ambient temperatures.
The straightforward approach that only requires the naked eye to inspect for potholes, cracks, spalling etc. This is a good starting point, however, this approach does not provide a proper assessment of what is happening on the interior, and only analyzes issues in need of immediate repair. Damages are easy to take note of, but the most costly at this stage.
Coring and Chipping
Even using non-destructive tests, coring and chipping may be needed to some extent to connect to the rebar or justify findings. Cores can also be used to analyze the mechanical and chemical properties of the concrete, as well as, its strength. All this information goes beyond the possibilities when using non-destructive testing. Although more can be learned through coring and chipping with added reassurance, there is a higher cost when taking apart the infrastructures one is attempting to maintain and repair.
Ground-Penetrating Radar (GPR)
This non-destructive test uses electromagnetic radiation to detect the reflected signals from subsurface structures. GPR assesses the quality and uniformity of concrete surfaces and deterioration on bridge decks using the reflective signals to detect changes in material, voids and cracks. This technology is well-suited for strict budgets and provides quantitative data as opposed to subjective.
Half-Cell Potential Test
This method assesses the voltage between the rebar in the concrete and an electrode placed on the concrete's surface. This method can detect corrosion before it progresses to the point of delamination, allowing the problem to be solved before ever arising. This test method is being innovated by many civil engineering firms, with Giatec at the forefront.
The company's XCell™ tablet is used to test the half-cell potential in concrete, and with its wireless communication capabilities, all the data is stored and shared to other connected devices, in particular, laboratories for a full analysis. The company has also released iCOR®, which for the first time ever, will not need direct connection to the rebar when measuring the corrosion rate. These two products would be of great help to the hypothetical bridge inspection initiative America should consider pushing forward.
With so many ways of inspecting current bridges, it is time to push for an initiative that ensures that these techniques are being used to their full potential. GPR technology is becoming more popular as it enhances inspection results; however, half-cell potential technologies are becoming more and more innovative each year. With companies like Giatec continuing to innovate, bridge inspection techniques should be advanced enough to make America's infrastructures safer and more durable.