According to a new report released by the American Road & Transportation Builders Association (ARTBA), 58,495 of the 609,539 bridges in America have been found to be ‘structurally deficient”. This key finding is based on the ARBTA analysis of the U.S. Department of Transportation’s recently-released 2015 “National Bridge Inventory” database.
According to the ARBTA Report this number represents over 2,500 less than reported for 2014, However at the current pace of bridge investment—it would take at least 21 years before they were all replaced or upgraded.
The bridges are rated on a scale of 0-9 with the top score of nine meaning ‘in excellent condition’. Bridges receiving a score of four or below are classified structurally deficient. Structurally deficient bridges are often posted with weight limits to restrict the gross weight of vehicles using the bridges to less than the maximum weight typically allowed by statute so they may remain in service.
The fact that a bridge is classified under the federal definition as “structurally deficient” does not imply that it is unsafe. A structurally deficient bridge, when left open to traffic, typically requires significant maintenance and repair to remain in service and eventual rehabilitation or replacement to address deficiencies.
According to NACE International corrosion is a leading factor in the degradation of bridges. NACE corrosion society currently has more than 30,000 members, many who specialize in corrosion control in highway bridges.
Not all bridge collapse or bridge failures incidents are caused by corrosion but corrosion poses a growing threat as bridge infrastructure continues to age and spending on maintenance and repair is put off.
According to the U.S. Department of Transportation, the federal government’s annual investment is less than two thirds of what is needed just to maintain roads and bridges and doesn’t cover improvements. As infrastructure deteriorates the cost of maintenance and repair increases, and the longer it takes, the higher and faster those costs rise.
Most bridges were built for a 50 year design life, which means state highway departments will have to maintain those bridges beyond their original design. This will be challenging because these bridges were then built to lower design standards than those used today.
This white paper, “Corrosion Control Plan for Bridges” by NACE International,
looks at bridges and what makes them corrode. It also discusses how employing relatively low-cost corrosion control measures during initial construction can produce low-maintenance bridges with service lives of 75 to 100 years. Corrosion control protects initial bridge investment and dramatically reduces maintenance expenses in the future.
As a member of NACE, Gamry Instruments supports corrosion research with electrochemical instruments designed specifically for corrosion applications. These instruments provide the highest level of electrical isolation. This means they are ideal for testing of grounded electrodes such as rebar in concrete found in bridges.