America has an infrastructure problem.
According to the American Society of Civil Engineers, the country’s roads, bridges, wastewater systems and other forms of infrastructure pull a grade of D+. Although the nation’s bridge infrastructure earns a grade of C+, about nine percent of the nation’s bridges are structurally deficient and seven percent of Ohio’s bridges are in need of major repair or replacement.
With a $440,000 research project funded by the Ohio Department of Transportation and Federal Highway Administration, University of Dayton civil engineering researcher Ömer Bilgin is developing a model and design methodology to allow for quicker and less costly bridge construction.
Bilgin, an expert in soil mechanics and foundation engineering, is advancing a model that will predict the temporary loss of load bearing capacity that can occur when piles (bridge foundations) are driven into the ground during construction. The piles, most often made of steel and concrete, transfer the loads of the bridge deep into the ground and are held in place by the frictional resistance of the soil against the pile.
The force of the piles driven into the ground disturbs the soil, which creates a temporary loss of load carrying capacity. Traditionally, contractors have had two choices: add additional length of pile and drive them deeper, or halt the pile driving and wait until the disturbed soil “sets up” and regains its strength. Both choices increase costs and delay construction.
“The associated costs can be hundreds of thousands of dollars on these big projects,” Bilgin said.
Bilgin and his team plan to review and analyze bridge construction data from Ohio and three surrounding states over the past 15 years to look for correlations between the types of pile used, soil conditions and the time needed to reach the pile’s design capacity. The result will be a predictive model that they will then test and refine in the field by monitoring construction sites in Ohio over the next two years.
Over time, having a model to predict pile capacity gain will allow civil engineers to better design bridge foundations. Before proceeding with construction, contractors can eliminate the need to add additional lengths of pile or to halt pile driving to perform capacity testing.