In the wake of bridge collapses, it is normal to wonder what could be improved. Questions ranging from the strength of materials to the frequency of inspections are interwoven through conversations that try to understand how it happened and how to prevent it in the future.
Researchers at the Texas A&M Zachry Department of Civil and Environmental Engineering have worked to not only answer many of these questions but also to implement better building and maintenance changes in bridge construction.
The successful partnership between the Texas A&M College of Engineering (COE), the Texas A&M Engineering Experiment Station (TEES), the Texas A&M Transportation Institute (TTI) and the Texas Department of Transportation (TxDOT) has expedited the process of turning cutting-edge research into improved roads and bridges for the public.
Deicing and Drones
Dr. Anand Puppala, professor and director of the Center for Infrastructure Renewal (CIR), has made multiple contributions to bridge safety and inspections.
In the fall of 2023, Dr. Puppala and Dr. Surya S C Congress (former senior research engineer at CIR and current assistant professor at Michigan State University) detailed the feasibility of conducting 360-degree inspections of bridges using uncrewed aerial vehicles (UAVs). His team found multiple instances where the use of UAVs and 3D modeling increased efficiency and reduced the need for specialized crew and equipment.
“Drones are best used under the bridge deck with cameras mounted on top and bottom for full 360-degree imagery,” Puppala said. “They give high-quality data for bridge asset management, and we have demonstrated that work with an Alaska DOT project completed last year.”
Complimenting traditional inspections with these new methods can provide significant savings in time, costs and labor. The use of drones can be particularly beneficial on bridges that span difficult-to-reach areas like over canyons or large bodies of water.
In early 2024, Puppala published the results of a full-scale pilot study of a geothermal bridge de-icing system for in-service bridges in Texas. This project, which started several years ago, explored the full-scale geothermal systems for the deicing of a real bridge site in Ft. Worth during an arctic blast winter freeze, resulting in no ice or snow build-up.
“We’re looking to study a few more items on that project,” Puppala said. “We will be looking at optimizing the system, cost analyses and determining ideal bridges to use it on.”
Scales and Corrosion
Dr. Stefan Hurlebaus, professor and R.P. Gregory ’32 Chair, has performed multiple field studies and full-scale lab studies to improve bridge superstructures over the last few years.
In one study, he developed a bridge weigh-in-motion concept for Texas bridges to better obtain truck information like weight, speed, number of axles and axle spacing as they cross. Experimental testing was followed by field validation on in-service bridges.
Applying these methods to new and in-service bridges could improve management and public safety with more accurate truck traffic and bridge performance data. Lane closures could also be avoided with bridge weigh-in-motion as opposed to pavement weigh-in-motion.
In more recent work, he helped evaluate corrosion prevention and mitigation practices on Texas bridges. Corrosion is affected by environmental conditions, so mitigation strategies must be able to adapt.
“We visited over 100 bridges all over Texas,” Hurlebaus said. “We took a lot of non-destructive measurements like ultrasonic, ground-penetrating radar, and infrared thermography.”
This data, along with samples tested in the lab, were used to create a tool for determining the best prevention and mitigation methods across the state. Texas boasts many different environmental conditions ranging from hot and dry deserts in the west to cool and wet in the northeast and the temperate coastline of the Gulf of Mexico.
Hurlebaus explained that these tools not only inform on the best corrosion mitigation for different areas but also the corrosion risk of different areas. Smartly deploying mitigation efforts where they are most needed can lead to less strain on traffic because of fewer closures for maintenance and reduced bridge degradation.
New Anchors to Build From
Texas A&M has multiple projects currently underway with TxDOT. One project, led by Dr. Kinsey Skillen, assistant professor in civil & environmental engineering, seeks to vet new anchorage details for improved constructability and performance when connecting beams to columns in straddle bent bridge structures.
“Straddle bent structures are commonplace in Texas, supporting elevated roadways by using a large reinforced concrete beam to ‘straddle’ the roadway below. The beam ends are supported by equally large columns, with cross-sectional dimensions easily exceeding 8 feet,” Skillen said. “The problem is the beam needs to be formed and built in the air; tying reinforcement in this condition is time-consuming and inefficient.”
Skillen’s research team will test new beam-column connections utilizing new hooked and headed bar reinforcement details that will permit the reinforcing cage to be prefabricated and then flown into the formwork via crane and meshed with the column reinforcement.
“It’s a way to improve the joint performance as headed and hooked bars can provide a more efficient anchorage mechanism compared to current detailing practice,” Skillen explained. “The improved speed of construction and reduced downtime will now come stock.”
The research team will construct straddle bents and other bridge structures that could benefit from these new details at full scale, and they will be tested at the large-scale structural testing laboratory at the CIR.
“We’re going to build, cast and load the joint just like it would be in practice,” Skillen said. “We are going to put it through its paces by applying 590,000 pounds of downward force with our 590-kip MTS actuators to show that it will work in the field.”
“It is a 42-month project due to the size of the specimens and because proper anchorage details of reinforcement can never be overlooked,” Skillen said. “It’s critical we understand the behavior of this connection at full-scale as it transmits considerable load from the beam to the column.”
Funding for this research is administered by the Texas A&M Engineering Experiment Station (TEES), the official research agency for Texas A&M Engineering.