Menus Subscribe Search

Follow us


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

October 31 • 12:00 PM

In the Picture: SNAP Food Benefits, Birthday Cake, and Walmart

In every issue, we fix our gaze on an everyday photograph and chase down facts about details in the frame.


October 31 • 10:15 AM

Levels of Depression Could Be Evaluated Through Measurements of Acoustic Speech

Engineers find tell-tale signs in speech patterns of the depressed.


October 31 • 8:00 AM

Who Wants a Cute Congressman?

You probably do—even if you won’t admit it. In politics, looks aren’t everything, but they’re definitely something.


October 31 • 7:00 AM

Why Scientists Make Promises They Can’t Keep

A research proposal that is totally upfront about the uncertainty of the scientific process and its potential benefits might never pass governmental muster.


October 31 • 6:12 AM

The Psychology of a Horror Movie Fan

Scientists have tried to figure out the appeal of axe murderers and creepy dolls, but it mostly remains a spooky mystery.


October 31 • 4:00 AM

The Power of Third Person Plural on Support for Public Policies

Researchers find citizens react differently to policy proposals when they’re framed as impacting “people,” as opposed to “you.”


October 30 • 4:00 PM

I Should Have Told My High School Students About My Struggle With Drinking

As a teacher, my students confided in me about many harrowing aspects of their lives. I never crossed the line and shared my biggest problem with them—but now I wish I had.


October 30 • 2:00 PM

How Dark Money Got a Mining Company Everything It Wanted

An accidentally released court filing reveals how one company secretly gave money to a non-profit that helped get favorable mining legislation passed.


October 30 • 12:00 PM

The Halloween Industrial Complex

The scariest thing about Halloween might be just how seriously we take it. For this week’s holiday, Americans of all ages will spend more than $5 billion on disposable costumes and bite-size candy.


October 30 • 10:00 AM

Sky’s the Limit: The Case for Selling Air Rights

Lower taxes and debt, increased revenue for the city, and a much better use of space in already dense environments: Selling air rights and encouraging upward growth seem like no-brainers, but NIMBY resistance and philosophical barriers remain.


October 30 • 9:00 AM

Cycles of Fear and Bias in the Criminal Justice System

Exploring the psychological roots of racial disparity in U.S. prisons.


October 30 • 8:00 AM

How Do You Make a Living, Email Newsletter Writer?

Noah Davis talks to Wait But Why writer Tim Urban about the newsletter concept, the research process, and escaping “money-flushing toilet” status.



October 30 • 6:00 AM

Dreamers of the Carbon-Free Dream

Can California go full-renewable?


October 30 • 5:08 AM

We’re Not So Great at Rejecting Each Other

And it’s probably something we should work on.


October 30 • 4:00 AM

He’s Definitely a Liberal—Just Check Out His Brain Scan

New research finds political ideology can be easily determined by examining how one’s brain reacts to disgusting images.


October 29 • 4:00 PM

Should We Prosecute Climate Change Protesters Who Break the Law?

A conversation with Bristol County, Massachusetts, District Attorney Sam Sutter, who dropped steep charges against two climate change protesters.


October 29 • 2:23 PM

Innovation Geography: The Beginning of the End for Silicon Valley

Will a lack of affordable housing hinder the growth of creative start-ups?


October 29 • 2:00 PM

Trapped in the Tobacco Debt Trap

A refinance of Niagara County, New York’s tobacco bonds was good news—but for investors, not taxpayers.


October 29 • 12:00 PM

Purity and Self-Mutilation in Thailand

During the nine-day Phuket Vegetarian Festival, a group of chosen ones known as the mah song torture themselves in order to redirect bad luck and misfortune away from their communities and ensure a year of prosperity.


October 29 • 10:00 AM

Can Proposition 47 Solve California’s Problem With Mass Incarceration?

Reducing penalties for low-level felonies could be the next step in rolling back draconian sentencing laws and addressing the criminal justice system’s long legacy of racism.


October 29 • 9:00 AM

Chronic Fatigue Syndrome and the Brain

Neuroscientists find less—but potentially stronger—white matter in the brains of patients with CFS.


October 29 • 8:00 AM

America’s Bathrooms Are a Total Failure

No matter which American bathroom is crowned in this year’s America’s Best Restroom contest, it will still have a host of terrible flaws.



October 29 • 6:00 AM

Tell Us What You Really Think

In politics, are we always just looking out for No. 1?


Follow us


Levels of Depression Could Be Evaluated Through Measurements of Acoustic Speech

Engineers find tell-tale signs in speech patterns of the depressed.

We’re Not So Great at Rejecting Each Other

And it's probably something we should work on.

Chronic Fatigue Syndrome and the Brain

Neuroscientists find less—but potentially stronger—white matter in the brains of patients with CFS.

Incumbents, Pray for Rain

Come next Tuesday, rain could push voters toward safer, more predictable candidates.

Could Economics Benefit From Computer Science Thinking?

Computational complexity could offer new insight into old ideas in biology and, yes, even the dismal science.

The Big One

One town, Champlain, New York, was the source of nearly half the scams targeting small businesses in the United States last year. November/December 2014

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