Hidden Damage in US Bridges Could Place Public at Risk
More than 55,000 bridges in the United States need repair - roughly 9 percent of the country's 600,000 bridges. The top five states with the most structurally deficient bridges are Iowa with 4,968, Pennsylvania with 4,506, Oklahoma with 3,460, Missouri with 3,195, and Nebraska with 2,361. Americans cross these endangered structures 185 million times a day.
And for good reason. In 1980, the freighter MV Summit Venture had its radar fail in the midst of a thunderstorm. As a result, the ship collided with one of the Sunshine Skyway Bridge's support columns, causing the structure to collapse. Six cars, a truck and a Greyhound bus dropped 150 feet into Tampa Bay, and 35 people died as a result. The bridge was eventually demolished and a safer one erected in its place. The replacement opened in 1987.
Looking back over the last 50 years, such loss of life is unfortunately not all that uncommon. In 1967, just over a week before Christmas, 32 vehicles plunged into the freezing Ohio river when the Silver Bridge between Point Pleasant, West Virginia, and Gallipolis, Ohio, collapsed. It cost the lives of 46 people.
The Silver Bridge disaster is of particular interest simply because it points out a common problem for U.S. bridges: at fault was a 0.1-inch defect in a metal bar. This defect was missed in any inspection that was done of the bridge prior to this catastrophic disaster resulting in loss of life.
Hidden damage can cause unexpected, devastating and costly results. In another example, on August 1, 2007, 13 people lost their lives and 145 more were injured when a bridge supporting one of Minnesota's busiest freeways unexpectedly collapsed. The state and two contractors ultimately paid out more than $100 million to survivors and families of the victims. At fault was found to be an unseen design defect.
Departments of Transportations throughout the U.S., as well as the USDOT itself, have a responsibility to ensure that these bridges are safe, for all vehicles public and private that cross them. Part of the reason that bridges still pose a danger is that inspection technology, 50 years old and considerably outdated, is still utilized. These methods are manual in nature and often deliver subjective results. Structural defects are often missed.
When deterioration affects bridge structures, traditionally they are visually inspected for damage and cracks. Record is made of the damage, it is photographed, and then the bridge is given a health rating. The problem is that visual inspection methods can only take into account damage that is visible to the naked eye, which of course does not include a bridge's internal integrity. By the time deterioration is visibly apparent for inspection, structural damage has often reached severe levels.
This can be likened to a medical patient who waits until they feel sick in the chest with obvious symptoms, at which point they go and get a chest x-ray. The x-ray reveals a mass, and the diagnosis is stage 4 cancer. Had the patient had the x-ray earlier on, the cancer would have been discovered at a point where it was possibly curable. Bridge deterioration is similar to a progressive disease. If deterioration is caught early enough, cost can be saved in repairs and life of the structure can be extended - not to mention the fact that lives can be saved as the bridge is repaired before it becomes truly dangerous.
DOTs should seek out more modern and efficient bridge inspection technology, and it is certainly there to be found. There is newer technology, such as that available from Infrastructure Preservation Corporation (IPC), which can be employed in saving countless lives as well as billions in repairs by isolating structural faults before they become serious issues. For example there now exist robotic systems that utilize Geophysical Non-Destructive Technology (NDT) protocols that can peer through concrete and other infrastructures.
These methods can identify early stage deterioration and allow recommendation of repairs before the deterioration spreads, compromising the structure's ability to carry its design loads. Timely diagnosis allows planning and repair of early stage deterioration that is financially preferable in that it prolongs infrastructure service life expectancy.
An example of the application of new technologies is IPC's concrete and bridge crack inspection system. This service maps length, width and position of cracks on concrete structures. By mapping out cracks, the progression of deterioration in concrete can be easily seen, allowing repairs to be made early. The life of the structure is prolonged, substantial cost is saved and public safety is protected. Repairs can be managed by utilizing year-over-year comparisons of bridge crack progression.
Another example is their BridgeScan technology that replaces the manual inspection of a bridge deck and approach way by peering through the road surface up to 15 feet. Utilizing this technology affords that department of transportation quantitative data of not just the bridge deck but below the surface locating voids, water intrusion, rebar placement, delamination and deterioration. What's more these inspections are conducted for the same price that the DOT is paying for the manual inspections and with fewer lane closures or the need for heavy equipment.
Putting It Into Perspective
Utilizing more modern technology that could detect bridge structural problems before they become catastrophic issues, how many billions of dollars could be saved in having to rebuild whole structures? How many hundreds of lives could be saved because hidden damage is caught early before it endangers drivers?
Again, it is up to the local and federal DOTs to utilize methods that ensure the safety of travelers that use these bridges daily. In fact, if one looks at the stated purpose of the U.S. Department of Transportation, it reads:
"The mission of the Department is to: Serve the United States by ensuring a fast, safe, efficient, accessible and convenient transportation system that meets our vital national interests and enhances the quality of life of the American people, today and into the future."
The words "safe" and "efficient" leap to mind when reading this statement, especially when comparing them to the statistics stated at the beginning of this article. And lastly, the phrase "quality of life of the American people" certainly says it all.
In the future, I would love to be able drive across any bridge in the U.S. without a second thought.