ANKENY, Iowa — A pilot study on rural bridge weight limits funded by the U.S. soybean checkoff has resulted in some bridges having their load limits lifted, allowing farmers to re-access throughways they had relied on for the transportation of farm commodities, inputs and equipment.
The pilot project in Iowa, Michigan and Indiana, conducted by the Iowa-based Soy Transportation Coalition (STC), uses specially developed sensors to record data on how a bridge responds when trucks move across.
By acquiring a more detailed account of the weight and stress placed on a bridge, the guesswork is removed from the hands of transportation officials and provides potential to remove unnecessary weight restrictions that affect farmers and rural dwellers.
"The knowledge and methodologies gained from checkoff-funded studies, such as the accurate testing of bridges conducted by the STC, can improve safety and efficiency for farmers, processors and communities by providing more accurate testing methods of weight limits on existing bridges," said Tom Hammer, National Oilseed Processors Assoc. president.
Three rural Iowa bridges have had their load limits lifted by county departments of transportation following a recent study period. With nearly three-quarters of the nation’s 607,380 bridges in rural areas, STC Executive Director Mike Steenhoek sees the study’s expansion as critical to increasing transportation options for farmers.
"If a bridge is closed or load-limited, what would often be a five- or 10-mile journey can easily increase to 20 or 30 miles or longer," Steenhoek said. "Our goal is to see this more accurate way of testing bridges widely adopted in communities where the problem is more pronounced."
The STC is attempting to expand the program to other states by working closely with soybean boards in other states, he added. "We’ve reached out to the Illinois and Ohio departments of transportation to propose doing a project, but nothing has been agreed to. We’re still trying to move forward on this in the 13 states that comprise the STC."
He estimates each closed bridge can cost the average crop reporting district as much as $1.8 million.
The testing method for the study was developed by Iowa State University’s Bridge Engineering Center. A pilot project kicked off in June 2014 with the Michigan Soybean Promotion Committee (MSPC), the Michigan Department of Transportation, Saginaw County Road Commission and the governor’s office.
A pilot project was also launched in partnership with the Indiana Soybean Alliance (ISA) and the S-BRITE Center. The S-BRITE Center’s Field Research Team investigated three bridges, performing comparative load ratings using analytical and diagnostic field testing methodologies. Each system performed well and delivered consistent and accurate data, according to the ISA.
Employing a simple data acquisition system to capture actual strain values for loads could also prove helpful in maintaining a bridge safely open to all legal load traffic, the ISA noted.
"This is important to the ISA in representing the farmers’ interest, as well as to the states and counties who strive to maintain safe infrastructure networks for the traveling public," the organization stated in a news release posted on Purdue University’s website.
A checkoff leader and soybean farmer from South Carolina told the MSPC he has experienced firsthand the inconvenience of an impassable bridge because of a questionable weight limit posting.
"We’ve had to change our route completely because of a bridge. The last-minute shift cost us extra time and fuel we hadn’t accounted for," said Woody Green. "Especially around harvest season, or during a period when we’re shipping a crop, that makes a huge difference."
