Bridge to the future
Spanning the Columbia River, the Lewis and Clark Bridge links Washington State and Oregon, carrying more than 18,000 vehicles a day during the busy vacation season. But, when the bridge deck needed renovation several years ago, state highway authorities encountered several issues. Replacing the pavement lane by lane could take four years. By closing the bridge completely, construction would take only months but would affect commerce. Or, the bridge could be closed every weekend for six months. None of those options was acceptable.
Instead, project engineers tried a new construction technique that allowed them to keep the bridge open every weekday and only close it for 120 nights between 9:30 p.m. and 5:30 a.m. plus four weekends. And, rather than costing the states the originally estimated $27 million, the massive undertaking cost $17 million. “This was a showcase project,” says Jugesh Kapur, the state bridge engineer for Washington. “This is how bridges will be done in the future.” Given the age and condition of the nation’s 600,000 bridges, federal, state and local officials responsible for keeping traffic moving across the nation will need every new technology available to carry the load that is facing the transportation system.
Cheaper and faster repairs
Representatives from the Washington-based National Association of County Engineers (NACE) testified before Congress in September 2007 that 25 percent of bridges are structurally deficient or functionally obsolete. The cost to repair or modernize the country’s bridges is $140 billion, assuming all bridges are fixed immediately, according to a July 2008 report issued by the Washington-based American Association of State Highway and Transportation Officials (AASHTO). The report cites several factors that affect the cost to fix the bridge system, including age, deterioration, congestion, and soaring construction costs — including the price of steel, asphalt, concrete and earthwork, which, over the past four years, has risen 50 percent and is especially aggravated by the high cost of oil. In addition, as a result of the 2007 collapse of the I-35W bridge in Minneapolis, engineers are increasingly concerned with the need for preventive maintenance. Increasing traffic and loads are pushing officials to consider costly new bridges that force difficult resource allocation decisions.
While acknowledging the huge financial requirements to bring the bridge system up to standard, highway engineers also are pointing to new equipment, materials and techniques that can support the American bridge system. The Federal Highway Administration’s “Highways for LIFE” initiative helps disseminate information about techniques and materials that state and local highway programs are testing through experimental programs. “In the next five years, there is a tremendous need to restore America’s bridges,” says Byron Lord, LIFE’s program coordinator. “We have to look for ways to use our resources as effectively as we can. We try to look at the big picture and accelerate innovation.”
During the Lewis and Clark Bridge project, whole sections of the bridge deck were constructed alongside the existing structure. When the new section was ready for installation, crews cut out and removed a corresponding piece of the old bridge. Then, a machine hoisted the new section and put it in place. “It was like pulling an old chip out of a circuit board and putting in a new chip,” Kapur says. Except that the pieces weighed 200,000 pounds.
As a result, motorists who drove over the bridge in the afternoon and then drove back over the bridge the next morning would not have noticed any delays or felt any inconvenience, he says. Under normal construction conditions, the bridge might have been closed for days as the concrete cured. “It worked wonderfully,” he says, noting that the deck will not need to be replaced for another 30 years.
Information about the Lewis and Clark Bridge project has been included in the Highways for LIFE program to show how new technology reduced inconvenience to motorists, reduced construction time and substantially cut construction costs. “It was faster and safer for the motorist and the worker,” Lord says. “It saved time, money and lives.”
Simple but effective methods
Engineers for the nation’s counties, who are responsible for the majority of the nation’s bridges, often have to find creative ways to keep their bridges in working condition. For example, Brian Keierleber, county engineer in Buchanan County, Iowa, uses railroad flat cars to replace bridge decks on small rural roads and boxcars to replace culverts. “There’s a solution for every problem,” he says. “This might not be the right solution for everyone, but it’s an excellent answer for us.”
So far, Keierleber has replaced 14 bridges with railroad flat cars and is working on number 15. By laying the cars on top of concrete abutments, he meets all the federal guidelines for carrying loads and meets stress tests. The technique was developed in cooperation with the Iowa State University engineering department.
Today, he says, the biggest problem is finding enough of the flat cars that have been removed from service by the railroads because of age or obsolescence. “I admit that I’ve been guilty of spreading the word,” he says, about the growing demand from other counties.
Of course, Keierleber also has relied on a number of other techniques to repair bridges — particularly those that are essential to bringing county farmers’ produce to market — some of which were built when locals were riding in horse-drawn buggies in 1876 or driving Model T Fords in 1913. “Some of these are awfully old bridges,” he says.
For instance, he has used super-strong concrete to build bridge sections that are longer and lighter, and allows for faster replacement. He also has begun using pre-cast concrete beams. “The biggest problem is that the fabricators are extremely busy,” he says.
Material advancements help
In nearby Delaware County, Iowa, Mark Nahra, the county engineer, has been taking advantage of new techniques in timber construction, which costs less than concrete and steel and uses a renewable resource. In particular, he finds that pre-drilling holes in the timber allows for easier field assembly. New techniques in treating the wood also prevent problems with insects and rot that usually shorten the life of timber bridges. He also has been delving into pre-cast concrete to accelerate construction and reduce labor and material costs. “If we can cut two weeks off construction time, it is worth the extra cost,” he says.
In addition, Nahra uses more low-tech practices, such as overlaying timber bridges with asphalt to protect the planks underneath. “In our rural area, it’s sometimes hard to justify the cost of concrete,” he says. “Timber is less costly for us.”
By trying new materials and methods, Nahra is spending less than he might otherwise, but he still is spending as much money to complete 3.5 miles of construction as the county did to complete a 7-mile job in 2006 because material and fuel costs have risen so dramatically. For example, he says asphalt, a critical component in any transportation project, has risen from $200 per liquid ton in 2005 to $800 per liquid ton today. Fuel costs also have doubled, he says. “It’s not even close,” he says, “revenue is not staying with expenses. We have to give raises to our staff, but we’re not even keeping up with the cost of living. Fuel, health insurance. We’re not matching costs by any means.”
NACE President Susan Miller is concerned not only with the rising costs, but what she says are misplaced priorities in Congress and the media. “Our biggest concern is that people are too caught up about tweaking the inspections and the structural engineering and not considering our failing infrastructure,” says Miller, who also is the engineer for Freeborn County, Minn.
Since the collapse of the I-35W bridge in Minneapolis, a lot of attention has been focused on inspections, which she says is not really the issue. “We don’t need to spend more money to watch bridges fail,” she says. “We need funding to build new bridges and replace deficient ones.”
The nation is in danger of allowing roads and bridges to deteriorate, which could have consequences for the entire economy, Miller says. “Our transportation system is only as good as the weakest link,” she says. “If our bridges fail, they become the weakest link in the entire system.”
While acknowledging the need to restore the nation’s bridges in the next five years, Lord emphasizes the need for finding the technologies and practices that best use the dollars that are available. “A lot of this is asset management,” he says. “We need to make decisions to optimize the investment strategies.”
Lord argues that as more states use the advanced construction techniques that the Highways for LIFE program is advocating, the overall cost will decline, because of competition among contractors. “They will respond to demand,” he says.
His 3-year-old program helps evaluate the benefits of the new technology and benchmark the actual construction costs, so that other governments can evaluate whether the techniques work for them. “We think that communication is key, and then we add market analysis,” he says. “We are trying to capture innovation and accelerate its frequency of application.”
Robert Barkin is a Bethesda, Md.-based freelance writer.