Preserving Our Bridges

Today’s modern bridges, like the University Drive crossing of I-75 in Auburn Hills, are a critical part of today’s infrastructure. Photo by Mario J Quagliata
Today’s modern bridges, like the University Drive crossing of I-75 in Auburn Hills, are a critical part of today’s infrastructure. Photo by Mario J Quagliata
Today’s modern bridges, like the University Drive crossing of I-75 in Auburn Hills, MI, are a critical part of today’s infrastructure. Photo by Mario J Quagliata

When it comes to discussions about infrastructure, the underlying “stuff” that society often takes for granted, possibly the result of its ubiquitous role in facilitating just about everything we do on a daily basis, it’s not long before bridges become part of the conversation.

Nationwide, every state has hundreds if not thousands of these structures, many of them built decades ago and to standards that were seen as “state of the industry” at the time, but now, not so much.

Even with the pressure that comes from a perennial funding gap, the issue isn’t necessarily something that should greatly alarm the public.

“We have safe bridges in America,” says Adam Mateo, a bridge engineer with the Virginia Department of Transportation whose job includes dealing with an aging inventory of structures, many of them approaching or past their 50-year design life expectancy.

Mateo says that structures designed for 50 years may need to be kept functional for 100 years or more, perhaps even as long as 150 years.

Mateo stresses that his optimism is not without foundation.

“We know the bridges are safe, primarily because we have a national bridge inspection standard that is rigorous and we don’t let them get unsafe,” he says.

What is required, and jurisdictions like Virginia and elsewhere have largely adopted this approach, is a change of tactics that has shifted to more preservation work, extending the life of a bridge, while at the same time implementing new design changes that will make tomorrow’s bridges last even longer than they do today.

“We’re lucky in that we understand what makes bridges deteriorate,” says Mateo. “It’s salt, water and heavy trucks, with the dominant factors being salt and water. What happens is the steel members of the bridge corrode, concrete pops off and girders rust.”

Even better than knowing what makes a bridge deteriorate is the fact that Mateo and his colleagues nationwide know what to do about it.Added to the wealth of data that engineers tasked with the job of keeping bridges in a safe condition for use by the motoring public… is one stark fact: A good many of the bridges that were designed and built to last a half century have either passed that mark or are getting close to doing so.

In Michigan the bridge infrastructure issue may be typical of the rest of the country in that there is never enough money to complete all the maintenance work that “should” be done.

That said, officials like Kirk Steudle, director of the Michigan Department of Transportation (MDOT), say the situation is not nearly as ominous as one might begin to think, especially in light of perennial funding challenges that are likely to persist.

One justification for a positive frame of mind is that Steudle and his staff at MDOT, the people who are ultimately responsible for bridge inspections and maintenance, have and continue to prioritize their work in favor of bridges, even over roadways.

And for good reason.

Priority shifts to bridges

“Bridges have to stay open,” says Steudle, a construction engineer by training who joined MDOT in 1987 and became its director in 2006. “And in the last round of funding, we made those a priority, putting one of every four cents into bridge maintenance.”

That doesn’t mean life for a bridge engineer in the state is a perfect one. “Some are pretty bad,” Steudle admits. “But we have a five-year plan to get to a better place.”

In Michigan and elsewhere, the focus when it comes to bridge maintenance is taking an asset management approach to the problem, identifying bridges that require strategic fixes that would extend the life of the structure, especially before a bridge gets to the point where it has to be replaced.

Indeed, Steudle says preserving and prolonging the life of a bridge is nearly always a preferred choice, especially in the early life of a structure.

But even then, common sense comes into play. “If we have a bridge where the piers have about 25 years of life left, we’re not going to want to put on a 100-year bridge deck. What we want to do is match strategic investments, doing the right repair at the right time, which is what our definition of strategic investments means.”

Fix damage done by salt and water
Their strategy starts by spending money to fix damage that has been done over time by salt and water, creating a patch with materials and techniques that are intrinsically better than what was used in the past.

CoverStoryBut money is also dedicated to work that will stop the leaking in the first place with the use of better expansion joints, which is the source of the water damage.

That shift in thinking is, Mateo says, not necessarily reflexive in a nation that’s traditionally geared to “replacement” rather than fixing something.

“We have this culture that thinks this way,” he says. “As bridge engineers, we like designing and building new things. The preservation and repair and rehabilitation is a more challenging way of looking at things, but that’s where we are right now.”

What is an underlying constant in this new type of thinking is the “now is better” approach to maximizing the impact of a repair strategy.

“On the good bridges, things like washing them to remove the salt that is contributing to the corrosion, recoating the ends and waterproofing the membranes are all things that help extend the life,” says Mateo.

So does applying thin deck overlays, cleaning culverts and removing large debris in bridge deck channels, all designed to extend the life of a structure.

Another factor that comes into play when a bridge gets to the point where it does require a full replacement is to take what Mateo says is a lifecycle approach to the type of materials and techniques that are likely to add significant years to the structure’s life expectancy—perhaps 80 to 100 percent more years—but with a minimal extra cost.

An example might be a new bridge without an expansion joint but with stainless steel reinforcement and the use of concrete that doesn’t absorb water as much as what was used in an earlier design. It’s a little more money but the result is a bridge that will last a lot longer.

In Virginia, experts like Mateo say the rehabilitation and preservation of bridges can be done for about 15-20 percent of typical replacement costs, a significant return on investment, especially for something that has to be done if the wheels of commerce are to continue turning.

There is, however, an important point to make when it comes to bridge repair, one that Mateo says deserves attention.

“It’s important that we don’t pursue a ‘worst first’ approach,” he says. That means emphasizing preventive maintenance and taking a balanced spending approach.

“If we limit what we do to bridges that are in the worst condition, we won’t be able to extend the life of bridges,” he adds. “There has to be a balance here.”

Another stated priority is to tackle projects that have the largest impact to commerce and the public.

Report card shows some improvement
Andrew Herrmann, a now-retired bridge engineer who spent his entire career with Hardesty & Hanover, a Boston-based company that specializes in bridge work, was president of the American Society of Civil Engineers in 2012 and chairman of the committee that wrote the ASCE’s 2009 Report Card on Infrastructure.

Dr. Nizar Lajnef, an assistant professor of civil and environmental engineering at Michigan State University, is part of a team that has designed sensors that will be embedded in the Mackinac Bridge as part of a study.
Dr. Nizar Lajnef, an assistant professor of civil and environmental engineering at Michigan State University, is part of a team that has designed sensors that will be embedded in the Mackinac Bridge as part of a study.

Four years later, the 2013 version of the ASCE’s report had bumped up its 2009 “C” grade to “C+” while urging federal, state, and local governments to increase bridge infrastructure investments by $8 billion annually to address what its authors say is an identified $76 billion in needs for deficient bridges across the U.S.

Herrmann, who clearly has stayed current with an industry he has worked in all his adult life, says one of the problems inherent in funding for keeping an existing bridge functioning beyond its projected life is the lack of attention it delivers.

“There’s no ribbon cutting involved,” he says. “That could be part of it and politicians typically are in too short a cycle to be looking too far into the future.”

At the same time, he agrees with others in that there are better materials, including high performance steel and concrete, with which to build bridges that will last longer than their predecessor structures.

“Building a bridge with better materials and better design will be cheaper in the long run,” says Herrmann.

Bridge engineers are also putting science to work in coming up with better ways of inspecting the thousands of bridges that continue to serve Americans, one of the most iconic being Michigan’s Mackinac Bridge, which connects the state’s lower and upper peninsulas.

Dr. Nizar Laznef, associate professor of civil engineering at Michigan State University, is co-developer (with professor Shantanu Chakrabartty of Washington University in St. Louis), of a sensor that could help bridge operators do an even better job of keeping tabs on the condition of the structures.

Several of the prototype sensors are to be installed on the Mackinac Bridge as part of a demonstration project. The key benefit is the fact that the sensors operate on energy produced by the vibration of vehicles, which means they require little if any maintenance while delivering massive amounts of data that engineers will be able to use to keep the structure in tip-top shape.

In Georgia, the state’s Department of Transportation has partnered with Georgia Tech Research Institute to create robotic technology that will automatically detect and repair damaged roads.

The “Roadbot” device, which is fully automated and requires only a single operator, boasts a detection accuracy of 83 percent, giving states the potential to save significant amounts of money by taking a preemptive approach toward road maintenance. By preventing larger damage, the Roadbot could allow states to focus their resources on other projects.

Another example of technology at work comes in the form of a multifunctional bridge deck assessment tool that’s being developed in cooperation with the Federal Highway Administration’s Long-term Bridge Performance program. The organization is using a robot-assisted, remote controlled device—RABIT—to collect high-quality 360-degree images around a bridge deck. Sensors also use ground penetrating radar to “map” reinforced steel and other metallic objects below the surface and GPS sensors to mark the location of the data collected.

The device also uses impact echo and ultrasonic surface waves to evaluate the condition of concrete and the strength of the bridge’s deck, wirelessly transmitting the data collected to a computer for further analysis.

Drones tested to improve efficiency
In Michigan and elsewhere, officials have embarked on a two-year study that began last spring into the use of drones for inspecting bridges, a follow up to work done in Minnesota.

Investigation on the use of drones is also being conducted in Massachusetts, where a group is looking at the pros and cons, including any potential threats, to their possible use surveying construction projects.

In all, some 33 states have been involved in studies of the technology or helped with policy discussions and research.

In Michigan, a 2014 study was done by transportation officials in partnership with the Michigan Tech Research Institute, with findings suggesting that the use of drones could help in assessment of bridge decks as well as monitoring traffic.

The first study determined that drones are safe, reliable, less expensive and help keep workers out of harm’s way, Steven Cook, a Michigan Department of Transportation engineer, was quoted as saying.

“A traditional bridge inspection, for example, typically involves setting up work zones, detouring traffic and using heavy equipment,” Cook said. “(Drones) can get in and get out quickly.”

With cost estimates of a bridge deck inspection at $4,600 and a drone inspection (two people taking two hours) coming in at about $250, the returns are potentially impressive.

Ron Brenke, executive director of the Michigan chapter of the American Society of Civil Engineers, is familiar with the issues, although that doesn’t mean he has to be happy about what the profession he represents has to deal with on an ongoing basis.

And while he understands the need to keep bridges open, he says the practice of putting temporary supports on bridges is a troubling sight. “All we’re doing is kicking the can down the road,” says Brenke.

Money at the heart of the solution
At the heart of any sustainable solution is a formula for funding that will allow for the replacement, rehabilitation or preservation of bridges in the long-term.

This Alden Nash Avenue bridge as it crosses I-96, shows a “slide in” technique that has the structure assembled next to active lanes. When all is complete, the bridge is (relatively quickly) moved into place.
This Alden Nash Avenue bridge as it crosses I-96, shows a “slide in” technique that has the structure assembled next to active lanes. When all is complete, the bridge is (relatively quickly) moved into place.

“It is the funding,” says Brenke. “I know people are tired of hearing it but there’s really no other culprit. Our state officials are very involved in asset management and they have a good handle on the condition of every bridge. It’s not that we aren’t doing things the right way, it’s that we don’t have the money to do all that’s needed.”

A significant boost in funding that takes effect Jan. 1, 2017, will go some ways toward helping the cause, for roads as well as bridges.

In a document titled “Economic Impact of Transportation Investment,” MDOT says an investment of another $1.3 billion (a number higher than what’s actually been approved) would support 14,000 jobs annually, increasing personal income by $1.9 billion in two years and by $11.6 billion over 10 years.

It would also, according to MDOT figures, increase gross state product by $3.3 billion in two years and by $25 billion over 10 years.

Under the measures, a series of new road funding laws will raise taxes by $600 million a year, with an eventual reprioritization of another $600 million in state spending, a $1.2 billion a year boost in spending for roads and bridges.

The initiative is said to be the state’s largest transportation funding increase in more than 50 years, although it has faced criticism by those concerned with its potential effect on other areas of government investment.

As of Jan. 1 next year, gas taxes shoot up 7.3 cents a gallon, with diesel going up 11.3 cents. Five years later, in 2022, fuel taxes will be indexed to inflation.

Michigan’s current gas tax, 19 cents a gallon, is below the national average but higher than others because the state sales tax is applied to fuel.

That said, Michigan’s gas tax is set to be 13th highest in the nation, based on figures from the American Petroleum Institute.

The funding legislation also includes a 20 percent increase in registration fees for cars and commercial trucks.

On the actual short-term impact on construction, the legislation has included an extra $400 million, but it’s a one-time appropriation not likely to be repeated. What does kick in is an extra $50 million in revenue from higher fuel tax and registration fees, with a fully phased in, dedicated funding level of $600 million in 2018, $760 million in 2019, $944 million in 2020 and $1.23 billion in 2021, according to the House Fiscal Agency, a non-partisan body.

But there’s still a gap, an annual $800 million shortfall that experts say is ultimately needed.

Which may mean that the strategies and innovations engineers and others are doing throughout the U.S. will have to continue, at least for the foreseeable future.

Editor’s note: This is the fourth and final article in a series looking at Michigan’s infrastructure and the individuals and businesses that play a part in it.