Menus Subscribe Search

If Bridges Could Talk …

• October 29, 2009 • 5:00 AM

New monitoring systems should make smart bridges that let on when they’re feeling fatigued.

As rush hour traffic crawled across Minneapolis’ Interstate 35-west bridge on a sultry August evening back in 2007, the roadway’s central span suddenly gave way, plunging nearly 100 vehicles and 18 construction workers into the Mississippi or onto its banks. Although the emergency response was swift, 13 people died and 145 were injured.

An exhaustive 16-month investigation (PDF here) by the National Transportation Safety Board found that the gusset plates — responsible for holding the bridge’s joints together — were only half the thickness required to carry the structure’s typical loads. Moreover, modifications from previous construction projects plus the weight of construction equipment and materials added a fatal strain on the 30-year-old bridge.

But, says Jerry Lynch, a professor of civil and environmental engineering at the University of Michigan, “As unfortunate as that event is, it has called to attention the importance of infrastructure in the U.S. and the need to maintain it. This is not simply about safety. The economic prosperity of society depends on these systems.”

Just think about the impact the recent Bay Bridge closure could have on the San Francisco economy.

In any case, Lynch believes the tragedy will ultimately inspire both government and the private sector to invest in additional and enhanced technologies to improve how bridges are designed and managed.

Span Plan
He should know. Lynch is the lead investigator of a project exploring new technologies to enhance the field of structural health monitoring. With the exception of a few landmarks like San Francisco’s Golden Gate and St. Louis’ Cape Girardeau bridges, the vast majority of the nation’s spans currently lack any monitoring system.

Funded in part by a nearly $9 million grant from the National Institute of Standards and Technology‘s Technology Innovation Program, what some are calling a “smart bridge” system will make it possible to detect problems before they occur by alerting inspectors to structural deficiencies through a wireless relay system connected to the Internet.

And though the I-35 west bridge has since been rebuilt and now monitors everything from corrosion to temperature-induced structural changes, experts aren’t drawing parallels between the collapse and tracking systems such as the smart bridges project. Catherine French, for example, a University of Minnesota professor and the principal investigator charged with monitoring the new bridge, readily admits there are limits to what health monitoring can do.

Lynch says the I-35 disaster was extremely rare. “The far majority of collapses are caused by triggering events like earthquakes, scouring rivers or vehicular damage. You can’t prevent an earthquake or a barge hitting a bridge.”

But for avoidable problems, Lynch’s project, with its systems approach to structural health monitoring, cutting-edge materials and bridge health assessment tools, will improve both longevity and durability.

High-Performance Concrete
Credit the Romans for first harnessing the compressional power of concrete, making possible the columns we commonly associate with classical architecture. Unfortunately, in strain-prone structures like bridges, concrete’s brittleness can result in failure unless it’s bolstered with steel.

Enter ECC — engineered cementitious composite — a “bendable concrete” invented by one of Lynch’s colleagues, Victor Li, a University of Michigan professor of civil and environmental engineering.

“ECC is rather unique, because even without reinforcement, it can take a high amount of tension load unheard of in regular concrete,” Lynch says. While it deteriorates like most cement-based material, cracks in ECC are just a few microns wide, compared with hundreds of microns for traditional cement.

“When you have rain and de-icing salts on your bridges, you’re allowing a lot of corrosive elements to penetrate into your buried steel. ECC is therefore more resilient against corrosion of any steel that might be buried inside.”

Beyond its mechanical attributes, ECC can even quantify how its electrical properties change in response to how much strain the bridge is experiencing at a given moment.

“Using a standard volt meter you get at Radio Shack, I could tell you how much strain’s in that material just by measuring its resistance,” Lynch says. This “self-sensing” can reduce both cost and complexity of instrumentation.

Similarly, Lynch and his team are working on a spray-on sensing skin that can be painted or glued onto particularly vulnerable surfaces to measure both strain and the existence, location and severity of cracks. Using carbon nanotubes (think slender, spaghetti-like molecular structures), the stuff works like a distributed sensor.

“We can use this material to see how its electrical properties change under both load and chemical changes like the pH environment, which is intrinsically linked to corrosion.”

The “sensing skin” will not only cover a much higher surface area (and thus eliminate the need for dense arrays of physical instruments) than traditional monitoring devices, it’ll provide actual color-coded pictures, making it easier for analysts to address problems.

Up to now, one of the biggest challenges in getting cities and municipalities to incorporate health-monitoring systems has been the expense.

Part of this can be traced to the current methods for communicating data, which typically involves the use of costly cables to transfer sensor readouts to a computer that’s storing the information. By going wireless, communication between the sensors themselves as well as between a sensor and a centralized data repository not only eliminates the need for cables, but allows data processing directly at the sensor.

“We can avoid inundating the bridge owner with truckloads of raw data and just provide information they can act on,” Lynch says.

Complementing site-based monitoring, a fourth kind of sensor would be placed within test vehicles (probably driven by bridge owners) to measure the bridge’s reaction to the strain imposed by the car or truck. According to Lynch, there has yet to be an effective way to monitor how vehicle behavior directly impacts bridges. However, vehicle-equipped sensors will help engineers and analysts predict how long a given structure will last and play a role in improving future sensor systems as well as bridge design.

Coming Soon
Over the next five years, Lynch’s team will be testing out these innovations on a handful of small- to mid-scale bridges in Michigan and possibly a large suspension bridge, the recently built New Carquinez Bridge, an hour north of San Francisco.

When complete, the system will, for the first time, offer engineers and bridge operators a way to see with their own eyes just where the problems are. Commuters, though, won’t be aware of these advances — “unless they looked really hard,” Lynch says. “You don’t want vandals vandalizing your system.”

Sign up for our free e-newsletter.

Are you on Facebook? Become our fan.

Follow us on Twitter.

Add our news to your site.

Arnie Cooper
Arnie Cooper, a freelance writer based in Santa Barbara, Calif., covers food, travel and popular culture, as well as architecture and the sustainability movement. He is a frequent contributor to The Wall Street Journal's Leisure and Arts page; his writing has also appeared in Outside, Esquire, Orion and Dwell. He's working on a memoir about his childhood experiences in New York City.

More From Arnie Cooper

A weekly roundup of the best of Pacific Standard and PSmag.com, delivered straight to your inbox.

Recent Posts

September 1 • 1:00 PM

Television and Overeating: What We Watch Matters

New research finds fast-moving programming leads to mindless overeating.



September 1 • 6:00 AM

Why Someone Named Monty Iceman Sold Doogie Howser’s Estate

How unusual names, under certain circumstances, can lead to success.



August 29 • 4:00 PM

The Hidden Costs of Tobacco Debt

Even when taxpayers aren’t explicitly on the hook, tobacco bonds can cost states and local governments money. Here’s how.


August 29 • 2:00 PM

Why Don’t Men and Women Wear the Same Gender-Neutral Bathing Suits?

They used to in the 1920s.


August 29 • 11:48 AM

Your Brain Decides Whether to Trust Someone in Milliseconds

We can determine trustworthiness even when we’re only subliminally aware of the other person.


August 29 • 10:00 AM

True Darwinism Is All About Chance

Though the rich sometimes forget, Darwin knew that nature frequently rolls the dice.


August 29 • 8:00 AM

Why Our Molecular Make-Up Can’t Explain Who We Are

Our genes only tell a portion of the story.


August 29 • 6:00 AM

Strange Situations: Attachment Theory and Sexual Assault on College Campuses

When college women leave home, does attachment behavior make them more vulnerable to campus rape?


August 29 • 4:00 AM

Forgive Your Philandering Partner—and Pay the Price

New research finds people who forgive an unfaithful romantic partner are considered weaker and less competent than those who ended the relationship.


August 28 • 4:00 PM

Some Natural-Looking Zoo Exhibits May Be Even Worse Than the Old Concrete Ones

They’re often designed for you, the paying visitor, and not the animals who have to inhabit them.


August 28 • 2:00 PM

What I Learned From Debating Science With Trolls

“Don’t feed the trolls” is sound advice, but occasionally ignoring it can lead to rewards.


August 28 • 12:00 PM

The Ice Bucket Challenge’s Meme Money

The ALS Association has raised nearly $100 million over the past month, 50 times what it raised in the same period last year. How will that money be spent, and how can non-profit executives make a windfall last?


August 28 • 11:56 AM

Outlawing Water Conflict: California Legislators Confront Risky Groundwater Loophole

California, where ambitious agriculture sucks up 80 percent of the state’s developed water, is no stranger to water wrangles. Now one of the worst droughts in state history is pushing legislators to reckon with its unwieldy water laws, especially one major oversight: California has been the only Western state without groundwater regulation—but now that looks set to change.


August 28 • 11:38 AM

Young, Undocumented, and Invisible

While young migrant workers struggle under poor working conditions, U.S. policy has done little to help.


August 28 • 10:00 AM

The Five Words You Never Want to Hear From Your Doctor

“Sometimes people just get pains.”


August 28 • 8:00 AM

Why I’m Not Sharing My Coke

Andy Warhol, algorithms, and a bunch of popular names printed on soda cans.


August 28 • 6:00 AM

Can Outdoor Art Revitalize Outdoor Advertising?

That art you’ve been seeing at bus stations and billboards—it’s serving a purpose beyond just promoting local museums.


August 28 • 4:00 AM

Linguistic Analysis Reveals Research Fraud

An examination of papers by the discredited Diederik Stapel finds linguistic differences between his legitimate and fraudulent studies.


August 28 • 2:00 AM

Poverty and Geography: The Myth of Racial Segregation

Migration, regardless of race, ethnicity, gender, or sexuality (not to mention class), can be a poverty-buster.


August 27 • 4:00 PM

The ‘Non-Lethal’ Flash-Bang Grenades Used in Ferguson Can Actually Be Quite Lethal

A journalist says he was singed by a flash-bang fired by St. Louis County police trying to disperse a crowd, raising questions about how to use these military-style devices safely and appropriately.


August 27 • 2:00 PM

Do Better Looking People Have Better Personalities Too?

An experiment on users of the dating site OKCupid found that members judge both looks and personality by looks alone.


August 27 • 12:00 PM

Love Can Make You Stronger

A new study links oxytocin, the hormone most commonly associated with social bonding, and the one that your body produces during an orgasm, with muscle regeneration.


August 27 • 11:05 AM

Education, Interrupted

When it comes to educational access, young Syrian refugees are becoming a “lost generation.”


Follow us


Subscribe Now

Your Brain Decides Whether to Trust Someone in Milliseconds

We can determine trustworthiness even when we’re only subliminally aware of the other person.

Young, Undocumented, and Invisible

While young migrant workers struggle under poor working conditions, U.S. policy has done little to help.

Education, Interrupted

When it comes to educational access, young Syrian refugees are becoming a “lost generation.”

No, Smartphone-Loss Anxiety Disorder Isn’t Real

But people are anxious about losing their phones, even if they don’t do much to protect them.

Being a Couch Potato: Not So Bad After All?

For those who feel guilty about watching TV, a new study provides redemption.

The Big One

One in two full-time American fast-food workers' families are enrolled in public assistance programs, at a cost of $7 billion per year. July/August 2014 fast-food-big-one

Copyright © 2014 by Pacific Standard and The Miller-McCune Center for Research, Media, and Public Policy. All Rights Reserved.