Building Bridges to Better Infrastructure

This week is National Infrastructure Week. The origins of the week date back to 2013, when the American Society of Civil Engineers (ASCE) famously graded America’s infrastructure at a D+. Following that disappointing report card, a nonpartisan coalition of businesses, labor organizations, and policymakers started Infrastructure Week to raise awareness of the dangerous conditions and economic damage created by the disrepair of our roads, bridges, dams, utilities, and other infrastructure.

Led by a steering committee that includes the AFL-CIO, ASCE, Building America’s Future, the Brookings Institution’s Metropolitan Policy Program, the National Association of Manufacturers, the U.S. Chamber of Commerce, and the Value of Water Coalition, the week includes events and education to create conversation and bring about action to rebuild America’s infrastructure.

When people think of crumbling infrastructure, bridges are one of the first things that come to mind. Along with simple age, an area’s weather, deicing chemicals, poor initial construction or materials, and frequent heavy loads are the main reasons bridges need repair or replacement. Bridge collapses, though extremely rare, can be deadly, and we’ve all felt the quick relief once we’ve passed safely over a bridge that looks like it’s on its last legs (or girders). In fact, in recognizing National Transportation Week in 2014, President Obama noted that the United States has more than 100,000 bridges that are old enough to qualify for Medicare. While the typical lifespan for a bridge is 50 to 100 years, that is a lot of bridges approaching the need for replacement.

Regular inspections monitor the safety of bridges, and officials charged with planning for bridge repairs and replacements know the life expectancy of structures in their infrastructure inventory.

As with any infrastructure project, funding is critical. Depending on complexity, location, and length, a typical bridge replacement can cost $250,000 to $500,000. Governments are trying to do more with less, and that means bridges are often not replaced as soon as they should be, although repairs can extend a bridge’s life, as can posted weight limits. Once a bridge qualifies for federal funding, communities receive 80% of the construction cost (and often the design cost as well) and are responsible for the remaining 20% of the cost.

How do bridges qualify for funding? The National Bridge Inventory has a 9-point rating scale describing the major component condition of each bridge, with 0 being bridge closed, 4 being poor condition, and 9 being excellent. These ratings for the major components of each bridge (deck, superstructure, substructure) are then fed in to a formula known as the sufficiency rating, which is a ranking based on a 0 to 100 scale, with 100 being the best possible score.

The overall sufficiency rating formula is subcategorized such that 55% of a bridge’s potential points are based on its structural adequacy (condition ratings), 30% on the obsolescence of its design, and 15% on its importance to the public. Within the overall ranking, a bridge can also be described as structurally deficient (meaning that speed or weight limits must be posted to ensure its safety) or functionally obsolete (meaning that it no longer can handle its current traffic volume, speed, size, or that it lacks safety features like shoulders). Some, but not all, steel bridges may be also categorized as fracture-critical, which means that if one main structural element fails, the bridge could collapse. If a bridge’s sufficiency rating scores 80 or less, it qualifies for federal repair funding, and if it scores 50 or less, it qualifies for federal replacement funding.

Once funding is granted, bridge designers evaluate what materials to use to replace the old bridge. Current designs need to take more into account than ever before: Safety, cost, flooding, maintenance, traffic, pedestrians, bicycles, fishing, navigation, environmental impacts, and aesthetics all play into the final design.

The time frame for a bridge replacement or rehabilitation is generally three to five years, starting with qualifying for funding and continuing through design, regulatory hurdles, and construction. The schedule may be impacted by environmental issues such as nesting swallows or spawning fish or by difficulties with right-of-way or state or federal regulations.

To learn more about the status of infrastructure in your state, check the ASCE website. For more information about bridge replacement and rehabilitation, contact structural engineers Dave Pantzlaff, Hisham Sunna, and Dan Sydow.