College of Engineering News • Iowa State University

Opinion: Improved testing could reopen bridges

This story was originally published as an opinion piece by Woody Green, director of United Soybean Board,  for Transportation Topics News

Imagine pulling up to a bridge that you previously used but now is closed to you because of weight restrictions. What will you have to do to get to your destination? How far out of your way do you think you’ll go to complete a delivery or make it home?

Well, that is exactly the kind of scenario that happened to me just last year.

It was after harvest, and I was taking a shipment of soybeans to the local elevator. I arrived at a small, rural bridge that recently had been given a weight limit that I couldn’t clear. When that happens, it can be a lot more than just an inconvenience.

All it takes is one bridge closure to turn a 5- to 10-mile journey into a 20- to 30-mile one. I had to change my route completely. The last-minute shift ended up costing us extra time and fuel I couldn’t afford. And while a trip like this makes up just one part of what we do, for a truck driver approaching closed bridges daily, a situation like this can become even more serious.

Trucks are vital to a working farm, whether it be for delivering seed to the farmer or hauling the final product to the elevator. The same can be said about livestock such as hogs or cattle. Oversize trucks also can be necessary when bringing essential new equipment directly to the operation. If these trucks can’t cross a bridge, the chain reaction hurts everyone’s bottom line.

As a farmer, I know to prepare for unexpected surprises. But unlike floods, drought or hail, bridges and weight limits aren’t out of our control.

Bridge inspections are typically done visually. The overall condition of a bridge is taken into account, such as if the metal appears to be rusting or the wood rotting, as well as its age and design. Of course, safety is the No. 1 priority when making the final ruling on a bridge’s weight limits. But looks can be deceiving.

To see past the wear and tear on a bridge and get a reading of its true status, more accurate testing methods have been developed.

With funding from the soy checkoff, which is a percentage of product revenue collectively invested by soybean farmers, Iowa State University’s Bridge Engineering Center conducted one of these tests on three rural bridges in Iowa.

The process involves attaching sensors to certain strategic points on a bridge. The researchers then drove a truck across the bridge, and the sensors recorded the data. After processing the data, the researchers were able to definitively know how the bridge responded to the weight of the truck.

As it turns out, knowledge of a bridge’s actual capacity can be extremely powerful. Each of the three bridges had its load limit lifted. Just think of how much time and money could have been saved if those bridges never had weight restrictions. Just think of what this could mean nationwide.

There are 607,380 bridges in the United States. Of all those bridges, nearly three-quarters are located in rural areas. So it’s no surprise that my experience of approaching an unpassable bridge is not an uncommon one for both farmers and truck drivers.

However, when a study proved that three rural bridges were unnecessarily load-limited, should my experience be so common?

Well, yes and no.

There are significant fees associated with testing a bridge’s structural integrity to the degree that ISU’s method is able to do. And just as the added cost of our extra fuel for rerouting a delivery has to come from somewhere, so does the added cost of a more sophisticated test. It’s difficult sometimes for smaller towns to make this a priority.

Still, consider the possible number of bridges whose load limits are too low. Now consider the number of farmers and truck drivers that could be positively affected by raising those limits. Suddenly, it becomes easier to see that the test could potentially pay for itself in saved fuel and time.

The bottom line is the U.S. transportation system is a major contributor to our overall economic success and gives us a significant advantage over our international competitors. Especially in agriculture, our ability to be efficient and reliable when providing customers overseas with product is one of our single best assets.

Achieving this edge wasn’t easy, and maintaining it is no different. It takes time, research, investments and hard work to stay on top. But if we allow part of this system to deteriorate, the effect on our industry would be devastating.

One way to avoid this happening is by getting precise information on actual bridge limitations to keep as many of them open to large trucks as possible.

I am passionate about the agricultural industry and the effects deficient bridges have on my fellow farmers. But that is just a single piece of the big economic picture. For one of us to succeed, we must all succeed. All aspects of our transportation system — highways, bridges, waterways, railroads — need to work together to continue making improvements and keep our infrastructure on top.

The United Soybean Board, based in Chesterfield, Missouri, is made up of 70 volunteer farmer-directors who oversee the investments of all U.S. soybean farmers in research and promotion projects.