Last week, the University of Maine Advanced Structures and Composites Center unveiled a rapidly deployable bridge system that utilizes composite material girders and precast concrete deck panels to reduce the time and logistics to build a bridge. According to the university, with this new patent-pending system, a lightweight highway bridge superstructure can be built in just 72 hours.
The system is composed of precast concrete panels over an FRP girder. The girder is reinforced with a hybrid composite containing thermoset resin, glass fiber and carbon fiber. The composite materials themselves were vacuum infused in a 3-D printed mold. According to Anthony Diba, a graduate research assistant working on the project as part of his master’s thesis, the system incorporates a unique shear connection that allows the precast panels to be connected onsite.
“We wanted to introduce something innovative but at the same time contractors are comfortable building with,” said Diba.
During a July 12 event at the center, UMaine staff, along with engineers, Maine Department of Transportation officials, business leaders, investors, researchers and members from Advanced Infrastructure Technologies (UMaine’s licensee for the now-famous “Bridge-in-a-Backpack” technology) watched as a bridge span was strength-tested in the laboratory using computer-controlled hydraulic equipment that simulates the heaviest highway truck loads.
The strength-test was conducted for the first time to prove the design modeling predictions and to demonstrate the bridge system can withstand the truck loading specified in the American Association of State Highway and Transportation Officials (AASHTO) Bridge Design Specifications.
In addition to significantly reducing construction time and logistics, the new bridge girders are designed to last 100 years, and the precast concrete deck is designed to be easily removed and replaced. The bridge system can be used for highway bridges, pedestrian bridges and military applications. The design is targeted for short- to medium-span bridge applications, up to 80-foot unsupported spans.
“[The] bridge test exceeded our expectations. The composite bridge withstood forces equivalent to more than 80 cars stacked on top of each other, and more than 5 times the HL 93 design load specified by AASHTO. The composite bridge girder exceeded twice the collapse strength of steel and concrete girders. Today was truly a remarkable engineering achievement made possible by research sponsored by the U.S. Army Corps of Engineers and the dedication and hard work of University researchers,” said Dr. Habib Dagher, executive director of the UMaine Advanced Structures and Composites Center.
As Dagher explains, the system takes advantage of the unique properties of both composite materials and precast concrete, and is designed with construction logistics in mind. The bridge girders weigh just 1-2 tons for 40- to 80-foot spans and can be erected with locally-sourced common rental cranes, making them easy to deploy in most locations.