Everything You Need to Know About America’s Crumbling Bridge Conundrum

February 13, 2012 | Infrastructure

During the early twentieth century, America built one of the greatest infrastructures in history. The bridges were built to last, but America hasn’t kept up with its legacy. Bridges built for 1925 traffic are falling apart, and it seems almost too late to fix them. After the collapse of the I-35W bridge in Minnesota in 2007, citizens, officials, and even civil engineers were shaken — just what will it take and how much money will it cost to correct the damage done by age, time, and impact across the country? The following information provides everything you need to know about America’s crumbling bridge conundrum, including a report card on current conditions, cost to repair, and possibly next-gen solutions.

The Report Card

I-35W Bridge Collapse

How can we not start this inspection with the American Society of Civil Engineers (ASCE)? This organization, founded in 1852, currently represents more than 140,000 members of the civil engineering profession worldwide. Additionally, it is America’s oldest national engineering society. In a mission to serve the public good, this organization issues a report card every four years on the state of America’s infrastructure. The last report in 2009 wasn’t stellar — the overall grade was a “D,” and bridges landed a solid “C.”

In this ASCE report, you can learn that:

  • The average bridge in this county was built to last 50 years, and that most of them are now 43 years old.
  • Of the 600,905 bridges across the nation as of December 2008, 72,868 (12.1 percent) were categorized as structurally deficient and 89,024 (14.8 percent) were categorized as functionally obsolete.
  • To put it bluntly, approximately one in four rural bridges, and one in three urban bridges were deficient.

Just to clear this issue up a bit, the ASCE defines “structurally deficient” as a bridge that may be closed or restricting traffic in accordance with weight limits because of limited structural capacity — but it’s not unsafe. A functionally obsolete bridge has older design features and geometrics, and though not unsafe, cannot accommodate current traffic volumes, vehicle sizes, and weights. These restrictions contribute to traffic congestion, and they force emergency vehicles to take detours. They also force school buses to take longer routes.

Take note that the I-35W bridge was labeled “structurally deficient” for 16 years before it collapsed, killing 13 people and injuring 145 more. But, on the riverbank where everything fell apart in 2007, a model for building the future may be coming together with the use of innovative materials and a new bridge with an expected life span of 100 years. The cost, however, is more than $230 million.

Funding Bridge Needs

Cypress Street Viaduct

States are responsible for infrastructure, including bridges, and they use federal as well as state and local funds for upkeep and improvements. According to the American Association of State Highway and Transportation Officials (AASHTO):

  • A total of $10.5 billion was spent on bridge improvements by all levels of government in 2004.
  • Nearly half, or $5.1 billion, was funded by the Federal Highway Bridge Program
  • $3.9 billion from state and local budgets and an additional $1.5 billion in other federal highway aid.

AASHTO estimated in 2008 that it would cost roughly $140 billion to repair every deficient bridge in the country — about $48 billion to repair structurally deficient bridges and $91 billion to improve functionally obsolete bridges.

Just maintaining the status quo — not allowing the backlog of deficient bridges to grow or accounting for damages from natural or man-made disasters — would require a combined investment from public and private sectors of $650 billion over 50 years for an average annual investment level of $13 billion. The cost of eliminating all existing bridge deficiencies as they arise over the next 50 years is estimated at $850 billion in 2006 dollars, equating to an average annual investment of $17 billion.

You may see the problem defined by this budgetary issue. If bridges were built to last 50 years, then maintaining the current status quo on those bridges would take them to twice their life span. In other words, something’s got to give — and it shouldn’t be the bridge. What is needed is new information technology, fresh engineering, and advanced materials. These next-gen projects can be built smarter and prove more resilient than current bridges; but, do current engineers and construction workers know how to get the job done?

Next-Gen Projects and Materials

Sundial Bridge

Popular Mechanics ran a special section on Rebuilding America in 2010, and an article within that special report showed how Americans could rebuild various components within that infrastructure. According to this article, we can build bridges better by using high-performance concrete, steel, and composites. On top of this mix, add an automated monitoring system to watch for deterioration in these smarter designs. Some of the materials involved include:

  • Super Steel: High-performance steel has been used since 1998. A new version has a minimum of 70-ksi-yield strength significantly outperform previously used bridge steels in strength, weldability and fracture toughness at low temperatures.
  • Fiber-Reinforced Polymer: An alternative, fiber-reinforced polymer (FRP) grids, has been built into dozens of demonstration projects in the United States. The oldest is 11 years and shows no sign of corrosion.
  • More Durable Road Surfaces: A new concrete developed at the Missouri University of Science and Technology may last 100 years and withstand up to 30,000 psi of pressure — nearly eight times as much as ordinary material. They also plan to introduce a “Con-Struct Bridge System” at their conference this year that includes self-healing materials.
  • Sensors: Periodic inspections and report cards can be supplemented by permanent sensors that detect flood possibilities and measure temperature, vibration, humidity, and other conditions. The Smart Brick, a wireless system from the Missouri University of Science and Technology, does all of this.
  • FRP Pilings [PDF]: Workers create traditional pilings by driving steel forms into the ground, filling them with concrete, timber, and rebar. More durable and corrosion-resistant pilings are created by pouring concrete into FRP forms at a factory. The units are then brought to the site and driven into the ground.

The problem with using any new products and plans may be curtailed by lack of funding if the surface transportation bill isn’t sufficient to curtail current damage or doesn’t allow for remodeling bridges.

Politics and Bridges

Gross Weight

There are few bridges in politics these days, it seems, as a bipartisan movement delays bills, reinforces earmarks, and avoids issues that concern the safety of American citizens. Such an issue is represented by the surface transportation bill, introduced in late January. Several disturbing issues are apparent in this bill, including:

  • A proposal to increase maximum truck weight by more than 20 percent. Trucks carry significantly heavier loads than automobiles and exact more wear and tear on bridges.
  • Another claim is that this bill is “loaded with giveaways to road builders, shortchanging transit, anyone who walks or bikes, as well as public health and the environment.”

The American Trucking Associations favor the bill, as well as the Transportation Builders Association, which is about right, considering the complaints. On the other hand, the Association of American Railroads plans to fight some provisions — and that makes sense as well, as they are battling truck transport in the freight business. But, that fight is logical, as it agrees with the issues brought forward by the ASCE regarding truck traffic. Additionally, according to the AASHO Road Test, heavily loaded trucks can do more than 10,000 times the damage done by a normal passenger car.

With that all said, a one-sided bill that favors rebuilding at the cost of losing some semblance of balance isn’t very progressive or visionary. The underlying fear is that the bill will restrict the use of new materials and the use of more modern design in favor of traditional building methods. The resultant loss will belong to the taxpayers, who will have to live with the fear of using insufficient infrastructure.

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