Texas has hundreds of bridges, most of which are concrete. After some time, bridges deteriorate or may get damaged, and a University of Texas at Arlington researcher is working with the Texas Department of Transportation to inspect, evaluate and monitor bridges to ensure their safety for years to come.
Nur Yazdani, a professor in UTA's Department of Civil Engineering, recently was awarded a three-year, $735,133 contract to inspect and evaluate new and existing concrete bridge components using non-destructive methods. He will also determine the true load capacity of bridges to ensure that the posted capacities represent what the bridges are capable of supporting.
According to Yazdani, most bridges are designed to last 50 years or longer, but many factors, such as cracking or spalling concrete, deterioration of the steel reinforcement inside or design or construction issues, may reduce their capacities and useful lives.
Yazdani will use non-destructive techniques, or NDT, including ground-penetrating radar, thermal imaging and ultrasound tomography, either alone or in combination, to test 30 bridges in the Dallas-Fort Worth metroplex. These methods will detect cracks, corrosion, damage or other issues without harming the bridge, and allow Yazdani and TxDOT experts to quickly and accurately determine the best course of action to remedy any deficiencies through repair, strengthening or replacement.
To determine load capacity, Yazdani and his team will use a computer model to conduct a multi-parameter study by manipulating materials, span length and other key measurements. They will then conduct a real-life test where they measure a bridge, close the highway for short periods of time and park a loaded truck on the bridge. They will measure the bridge again to see how much it flexed due to the weight of the truck and compare those results to the model's prediction. If the numbers don't match, it indicates a problem that TxDOT can then address.
"This is really a cost issue. Our research will help the state save money and ensure that Texas bridges are safe. Any time you can save money without compromising safety, it's desirable," Yazdani said.
"Making safer structures makes transportation safer and benefits the community as well. If a bridge suffers a catastrophic failure, there's a huge cost in terms of financial, time and social losses, so anything we can do to make it easier to inspect bridges and quickly address issues beforehand is important."
Yazdani and his team have been testing the performance of a carbon-fiber-reinforced polymer wrapping for future bridge repairs through another $598,953 existing contract from TxDOT. Already in use in about 25 state highway departments including TxDOT, the laminate is less than one-half millimeter thick and stronger than steel. If concrete deterioration or damage is detected, workers prepare the concrete surface, spread epoxy glue over the surface and the CFRP laminate, then place the wrap on the glued surface. The performance of the CFRP wrapping is being investigated through NDT methods in the laboratory and also on full-scale highway bridges.
"The CFRP laminate doesn't corrode, has a high durability, and whatever member strength was lost due to damage/deterioration is more than regained by the laminate application. It is also easily installed and doesn't affect the bridge height or clearance for any vehicles passing below. If it performs as expected, this could make repair and maintenance of bridges much easier, less costly and durable," Yazdani said.
Yazdani's research is one example of the research in the area of sustainable urban communities, one of the themes of UTA's Strategic Plan 2020 Bold Solutions |Global Impact, said Ali Abolmaali, professor and Tseng Huang Chair of the Department of Civil Engineering.
"Bridges and overpasses are key elements of the highway system in the Dallas-Fort Worth area. Structural issues that force closures cause massive disruptions to transportation and commerce. Dr. Yazdani's work will help TxDOT identify and correct problems before they get to that point, keeping our highways open and flowing smoothly," Abolmaali said.