Researchers discover solutions to build stronger bridges

Aging infrastructure is a major issue in the U.S. with nearly 50 percent of bridges considered in poor condition—nearly 12 percent are over 80 years old; 42 percent are over 50. Many have high volumes of traffic.

Investments are often for immediate repairs, but today engineering researchers are exploring how structural changes might improve longevity, safety, and construction costs.

One structural study done by researchers at Rochester Institute of Technology found that reorienting piles, the legs or foundation, of bridge structures, nearer to the main abutments can increase the service life of a bridge. The optimized design can better withstand seismic forces and temperature variations, said Amanda Bao, professor and interim department chair of RIT’s Department of Civil Engineering Technology, Environmental Management and Safety in the College of Engineering Technology.

“We found that reorientation reduces load demands that degrade the materials,” said Bao, who worked with civil engineering technology undergraduate students Albert Petry and James Warren this fall and co-authored the paper, “Optimizing steel pile design in integral abutment bridges.” Results were published in the Proceedings of Geo-Structures 2024 and presented at the recent ASCE Geo-Structures Conference in late November in Pittsburgh.

Conventional bridges consist of a bridge deck (surface), girders (deck supporting components), and abutments with expansion joints at the girder ends. Abutments, the attachments at each end of a bridge, connect the main structure with the ground and bear the structural load. 

Due to the location of the expansion joints, girders have the most deterioration because of gaps where moisture and de-icing chemicals seep in and erode both the girder ends and the abutments.  Newer integral abutment bridges have the girder ends fully encased into the concrete abutment walls at the ends of the bridge and have been found to significantly decrease erosion by eliminating the expansion joints.

“The pile orientation is the main focus of our study because we found that each state has a different practice, and it is very inconsistent across the U.S.,” said Petry, a fourth-year student from Merrimac, Mass. “We wanted to know if there is a preference that should be established? Is there a more economical orientation for different areas?”

To explore those questions, the researchers built a computer model representing a bridge 130 feet in length, 57 feet wide and fully integral abutments with 40-foot-deep piles. Different forces that impact the structure were applied to the digital model. Model results focused on several critical factors in bridge design—displacement, or movement, at the top of the piles, comparisons between the year-long temperature changes, and seismic zones, then overlaying the assessments along the two different bridge pile orientations.

“There are two ways to orient the steel H-piles with the first web of the H-pile being parallel to the flow of traffic, a longitudinal direction. The second orientation is a rotation of 90 degrees, the web perpendicular to traffic flow. That rotates the strong axis of the pile, and it changes the load it can accommodate,” said Warren, a fourth-year student from Montgomery Village, Md. “We then tested which orientation would be best for certain areas where temperature changes and seismic forces control the design.”

They found in zones where temperature changes dominate, the longitudinal direction (parallel to the flow of traffic) reduces displacement and load. This indicates the structure is stronger. For zones where seismic forces are prominent, the opposite orientation, the web of the H-pile perpendicular to the flow of traffic, has the lower displacement and load.

This data can provide guidelines and refine the best practices used by engineers and bridge designers to form consensus across the U.S., said Bao.

The undergraduate research experience that Albert and James gained significantly enhanced their critical thinking skills. They were able to apply what learned in class to investigate something new and contribute to the cutting-edge knowledge in the civil engineering field.” she said.