Iowa State’s Bridge Engineering Center and the Iowa Department of Transportation are collaborating to bring three ‘smart bridges’ to Des Moines. The bridges contain sensing equipment to measure the amount of pressure exerted on them.

One bridge on Interstate 235 in Des Moines is finished and two more are nearing completion.

“They’re all 90 percent done,” said Ahmad Abu-Hawash, chief structural engineer of the transportation department’s Office of Bridges and Structures. “The pedestrian bridges are done but not open to traffic.”

The three bridges, one for automobiles over 12th Street, and two pedestrian bridges, one over 40th Street and another over 44th Street, have been equipped with fiber-optic monitoring equipment that detects weight and strain when an automobile or a person crosses.

“Different sections of the bridge stretch a little bit. We’re using fiber-optic strain sensors to measure the strain,” said Michael LaViolette, bridge engineer for the engineering center and associate scientist for the Center for Transportation Research and Education.

Brent Phares, associate director for the engineering center and Center for Transportation Research and Education, said the sensors pick up changes in light to take the measurements.

“One of the new sensors is a fiber-optic-based system,” he said. “It uses light waves that are sent down a piece of fiber-optics.”

Phares said the sensors have only recently been put into use.

“They’ve been in development for five years or so,” he said. “We have only really started to use them for practical uses in the last 18 months.”

Abu-Hawash said the bridges are owned by the Department of Transportation but have a connection with the Bridge Engineering Center for Information and Research.

“The Bridge Engineering Center has special expertise in monitoring,” he said. “We have a relationship where they help us with some research, so it’s pretty natural that we would go to them for help with this.”

According to a press release, the monitoring research was funded through a $155,000 grant from the Federal Highway Administration’s Innovative Bridge Research and Construction Program as well as $50,000 from the Iowa Department of Transportation.

LaViolette said the 12th Street bridge was made with high-performance steel which will hopefully make the bridge last longer.

“Its a little higher strength than your typical steel,” he said. “But it’s more of a durability issue than a strength issue.”