PULLMAN, Wash. – About one third of the 600,000 bridges in the U.S. are in need of repair or replacement due to deterioration and damage, including that caused by vehicle collisions. A Washington State University civil engineer is applying his expertise in aerospace techniques to create an inexpensive solution to this growing problem.
Based on a previous study conducted by him and his colleagues for the Ohio Department of Transportation and Federal Highway Administration, Pizhong Qiao, professor of civil and environmental engineering, sandwiched aluminum and layers of honeycomb material to create impact-laminate (I-Lam) panels. The system protects bridges by absorbing the energy from collisions. In addition, data collected from attached sensors can help prevent future collisions.
If successful, the panels could be a major breakthrough in bridge protection and could be implemented nationwide, Qiao said.
Energy absorption
The panels – filled with layers of honeycombed compartments – cover the underside girders and sides of a bridge, he said. In a collision, the compartments are crushed, destroying the panel but saving the bridge.“This is a sacrificing type of system,” he said. “The I-Lam sacrifices itself to protect the bridge girders underneath.”
After the collision, the panel can easily be replaced, which saves the hassle and expense of repairing the bridge, Qiao said.
“Here at WSU, we are the first to apply an I-Lam system like this,” he said. The honeycomb is used in aerospace technology as an energy-absorption system, but it hasn’t been applied much like this, he said.
Detection system too
The panels also help detect and monitor collisions, Qiao said. Attached smart piezoelectric sensors trigger remote data collection when panels are hit. Damage is reported early and data is collected to make improvements.
“The proposed detection system is capable of triggering a camera to catch the collision,” he said. “Knowing what types of vehicles collide with bridges may help develop future collision prevention strategies.”
Collaboration in field trial
Late last year, Qiao – in collaboration with Prof. J. Leroy Hulsey of the University of Alaska Fairbanks – received a $200,941 grant from the Alaska University Transportation Center to begin testing and implementing the I-Lam system in cold-weather regions. With analytical modeling and lab testing under way at the WSU Composite Materials and Engineering Center through May, Qiao plans to begin field tests in Alaska, Montana, Idaho, Oregon and or Washington after that.
The Washington State Department of Transportation has shown interest in the proposed system, as many bridges in the state have been hit by overheight trucks. In collaboration with WSU, the state agency is helping identify a bridge site at high risk for truck collisions where a trial of the I-Lam system could be conducted. The field implementation is anticipated as early as this summer.
The challenges of cold weather
Although the panels can be used in other climates, cold-weather regions pose particular challenges to monitoring and repairing bridges after collisions, Qiao said. Bridges often are in remote areas and the weather makes detection and repair difficult. Without repair, bridges can deteriorate.
“After a collision, the concrete girder will peel off, exposing the steel reinforcement inside,” Qiao said. “Exposing these reinforcements to the moist climate of these regions can cause permanent damage to the bridge.”
By preventing damage and alerting local authorities that repairs are needed, the I-Lam system will help extend the life of these structures.