Bridging the gap: Deterioration models to optimize bridge management

The state of Illinois has 4,154 bridges in need of repair, an increase from 4,083 in 2020, according to the National Bridge Inventory.

How can agencies make the best-informed choices for operating, maintaining and improving those bridges?

That’s what Illinois Center for Transportation and Illinois Department of Transportation seek to answer in a joint project, R27-238: BrM Quantity-Based Bridge Element Deterioration/Improvement Modeling and Software Tools.

Gongkang Fu, Illinois Institute of Technology professor, and William Beisner, IDOT’s statewide NBIS program manager, led the project.

The two developed deterioration curves — models that predict deterioration over time — based on inspection data of individual bridge elements, like abutments or girders, from Illinois’ bridge database.

The developed models will form the basis for IDOT’s bridge management system, which the agency will use to collect, analyze and manage data about Illinois’ bridges and make crucial decisions on their management.

The deterioration curves forecast the condition and life span of various bridge elements and will directly impact the quality of IDOT’s decision-making.

Fu’s team packaged the models into two user-friendly software programs for bridge owners.

They divided the programs into two categories: one involving significant renewal work (termed condition improvement) and the other involving minor or no renewal work (termed do-nothing deterioration), such as placing a deck overlay, painting or cleaning.

“The work marks the first time in the 20-some-year history of bridge management that condition deterioration and improvement are realistically captured based on bridge element ratings from routine inspection,” Fu said.

The tools allow IDOT to update the models as additional data is uploaded to the database.

“One tool will make it possible to monitor bridge element deterioration as it takes place as well as identify possible errors in inspection data when they occur,” Fu said. “Another software tool permits the DOT to optimize the selection of construction work for bridge element condition improvement.”

The research team validated the programs using two common bridge elements: reinforced concrete decks and steel girder beams. The programs confirmed the deterioration rates for the two items, validating their models.

Implementing the programs into IDOT’s bridge management system will help the agency to optimize bridge maintenance, preservation, rehabilitation or replacement.

“The research will aid in the planning/programming of IDOT’s bridge assets and helping IDOT spend the taxpayer’s money in the best way possible,” Beisner said.