Graduate students boost bridge efficiency

Behind the green barriers around the University Center pedestrian bridge construction site, University of Miami graduate students are in hard hats getting real-world experience with architecture and civil engineering by assisting with the bridge’s construction.

Antonio Nanni is a professor and chair of the department of civil engineering, as well as a researcher of construction materials and their structural performance. He and his team of graduate students are working together with Moss construction company to increase the efficiency of the bridge’s construction.

“As a student, for me, it’s really interesting to work on a real application of these materials… so we were really lucky that this year we had a construction of this bridge on the campus,” said Omid Gooranorimi, a civil engineering Ph.D student.

They are working with a structural engineer to use bars made of fiber reinforced polymer (FRP), a material researched in the Structures and Materials Laboratory in the College of Engineering, in place of standard steel reinforcements.

“I went to the civil engineering department and had the opportunity to meet and talk with Dr. Nanni… and he encouraged me to work with two Ph.D students in this project on the bridge,” said Carlos Morales, an architecture masters student.

“Deploying the technology we have been working on in our laboratory during the last decade gives credibility to the efforts and accomplishments of our students and faculty and, as importantly, shows the relevance of UM in addressing the sustainability challenges we face as a society,” Nanni said.

According to construction manager Kyle Conroy, reinforcements are needed because concrete lacks tensile strength, and steel is the material normally used for the reinforcement of concrete.

“Concrete is very strong in compression, meaning that if you push it together, it will push back,” Conroy said. “So it can hold a lot of weight if you stack something on top of it. It’s not very strong in tensile, which means that if you had something pulling it apart, it pulls apart relatively easily. That’s the reason you put steel into the concrete: to beef up the tensile strength. So when you pull it apart, the steel holds it all together.”

However, the team is substituting steel with FRP to decrease corrosion of bridge materials. Gooranorimi explained that the FRP material holds an advantage over steel because it doesn’t corrode, meaning it doesn’t lose its properties in corrosive environments.

Additionally, FRP is advantageous because it is much lighter than steel. This makes the physical labor of construction easier.

“[One guy] can pick up a one-inch thick bar,” Conroy said. “Normally, it takes like three guys to pick up a bar if it’s steel.”

“It really decreases the amount of… energy… and people for handling the same amount of the material,” Gooranorimi said. “So that’s why this material is special.”

While the FRP materials will experience some tensile stresses, they are not intended to be the bridge’s structural support system. Instead, they act as reinforcements for the concrete material itself.

“What’s holding up the bridge for the most part are those giant steel beams that go through the center of it,” Conroy said. “What the FRP is doing is holding the concrete together.”

Moss began plans for the bridge after the completion of the Shalala Student Center in spring 2012. Pre-construction for the bridge began in January this year, and workers mobilized on site in late May. The goal to complete the bridge is the end of September.

When it is finished, the bridge will be 13-feet-10-inches wide and 211-feet-7-inches long.

“We are most grateful to the UM Department of Facilities Design and Construction as well as the bridge designer and contractor for allowing us to contribute to the project and look forward to future collaborations on our own campus,” Nanni said.