Author: Marissa K Miller

By McCall Macomber, Illinois Center for Transportation

Illinois will receive $1.4 billion to repair its bridges in President Biden’s five-year, $27 billion Bridge Formula Program, which is designed to replace, repair and rehabilitate bridges across the nation.

The program will supplement Gov. JB Pritzker’s $45 billion “Rebuild Illinois,” an ongoing six-year plan to improve the state’s transportation infrastructure.

Key to both programs is a focus on not only rebuilding transportation infrastructure, but also constructing it to last longer.

Illinois Center for Transportation and Illinois Department of Transportation focus on just that in the joint project, “R27-197: Bond Characteristics and Experimental Behavior of Textured Epoxy-coated Rebars Used in Concrete Bridge Decks.”

Bassem Andrawes, University of Illinois Urbana-Champaign CEE professor and Excellence Faculty Fellow, leads the effort to build longer-lasting bridges with Daniel Tobias, IDOT engineer of concrete, soils and metals, and Jayme Schiff, IDOT engineer of bridges and structures.

Their focus is on the coating of steel reinforcing bars (“rebars”), which are placed in concrete to strengthen bridges. If unprotected, rebars can experience excessive corrosion because of the infiltration of water and deicing salts through cracks in bridge decks.

Adding a smooth epoxy coating to rebars, a popular technique since the 1970s, significantly increases their resistance to corrosive materials, but also may generally lead to increased crack width in bridge decks.

Here the researchers investigate adding a roughened texture to the smooth epoxy coating, which increases friction as well as the bond between the concrete and bars.

“One of the issues with bridge decks is that they crack,” Schiff said, “and the expectation with this textured reinforcement is it will have less cracking and also hold the cracks tighter, so that’ll allow less chlorides to get into the bridge deck.”

Their goal? Find the optimal level of texture or roughness to add to the coated rebars.

“It’s like looking for just the right grit of sandpaper to sand your wood,” Tobias said. “We wanted to know if a smoother 220 (grit) or a rougher 40 (grit) was the best, or somewhere in between.”

To figure out the optimum texture, Andrawes isolated conditions bridge decks would experience in the field and re-created them in UIUC’s Newmark Structural Engineering Laboratory.

Andrawes started with taking microscopic images of various textured rebars and examining their surface profiles.

He and his team then embedded the rebars in concrete cylinders to test the bond between the bar and concrete.

Key to the research were several large-scale tests, where the researchers tested the cracking produced from shrinkage after the concrete was cast as well as thermal movement and flexural behavior.

Andrawes’ methods showed that cracks in the bridge were not as wide as those when using nontextured, coated rebars and the bridge deck was stiffer and had smaller deflections.

Ultimately, Andrawes’ team verified the textured rebars improve bridge deck performance by about 33 percent.

“This is the first time that these bars are applied anywhere in the world,” Andrawes said, “so IDOT is pushing the envelope of the application of epoxy-coated rebars.”

The innovative technology is expected to have a nationwide impact, as many state agencies are searching for a way to reduce the number and severity of cracks in bridge decks.

“Several state DOTs are aware of Illinois’ research on this topic and are eagerly awaiting results for their potential implementation,” said Dan Brydl, Federal Highway Administration’s Illinois Division bridge engineer and a member of the project’s technical review panel.

“FHWA is very pleased with the results of this research,” he added, “and this marketable innovation could very possibly lead to a new standard in bridge deck reinforcing steel coatings both regionally and nationally.”

Drivers in Illinois can also expect to see an additional benefit: fewer traffic delays because of less time spent on closing roadway lanes for bridge maintenance and repair.

“Our goal here is to reduce future maintenance of bridge decks and hopefully reduce costs over the life of a bridge,” Schiff said. “That’s the long-term goal: to help save tax dollars.”

 

Article from CEE website.

The deadly tornado outbreak that struck the central and southern United States in December 2021 killed 93 people and caused an estimated $3.9 billion in damages across eight states. In size and severity, the storms were unusual – but, experts say, getting less so. A new, multi-disciplinary research center announced this month at the University of Illinois Urbana-Champaign will work to mitigate the impact of such extreme wind events and build community resilience to the disasters they cause.

Extreme wind events, including tornadoes, hurricanes and derechos, account for more than 80 percent of all inflation-adjusted losses caused by natural and human-caused hazards in the U.S. Despite significant advances in weather prediction and detection, the number of billion-dollar weather disasters due to windstorms has increased from an average of two events per year in 1991 to more than 12 per year in 2021, according to the co-directors of the new center, Robert Trapp, professor of atmospheric science, and Frank Lombardo, assistant professor of civil and environmental engineering.

“Contrary to popular belief, we are not making a significant impact in reducing losses from the most extreme wind events,” Trapp said. “Losses will escalate due to increased exposure and exacerbations from climate change.”

The newly established Extreme Wind Resilience Center (EWRC) will bring together the necessary expertise to reduce those losses, organizers said. A joint effort between UIUC’s departments of Civil and Environmental Engineering and Atmospheric Sciences, the center will leverage world-class expertise from multiple disciplines.

“Our two departments are well suited to lead this effort,” Lombardo said. “We bring internationally recognized expertise in atmospheric science, wind science and engineering, and structural engineering.”

Activities are already underway in support of the EWRC mission, including a post-disaster reconnaissance mission to evaluate the damage from the December tornado outbreak. A group of graduate and undergraduate students from CEE and ATMS, under Lombardo’s supervision, spent three days in Kentucky investigating tornado damage in multiple areas along a 160-mile tornado track. The assessment provided key observations regarding tornadoes that will spur additional EWRC investigation and research.

One of these insights, Lombardo said, is that the overall risk from tornadoes is not well understood. The scope of the risk depends on prediction and preparedness before the storm, intensity during the storm, and recovery after the storm. The new center will deploy an end-to-end approach that considers this full scope of risk. The risk also spans all spatial scales from individual homes to community and regional levels. Some damage and loss of life is preventable even in the most extreme events through better building practices and proactive approaches to safety, such as storm shelters, Lombardo said.

Researchers from EWRC also will participate in the upcoming PERiLS project, a multi-institution field campaign designed to study tornadoes in the southeastern United States beginning on March 1. The aim of PERiLS (Propagation, Evolution and Rotation in Linear Storms) is to understand how “quasi-linear convective systems,” sometimes called squall lines, generate tornadoes. These systems are common to the U.S. southeast and Midwest, and are known to behave differently and present significantly greater forecasting challenges than “supercell storms.”

The ATMS team in collaboration with other universities and research laboratories will deploy several mobile weather radars, including Doppler On Wheels (DOWs) and the C-Band on Wheels (COW) from the new University of Illinois Flexible Array of Radars and Mesonets (FARM). FARM also includes an array of truck-borne mobile weather stations and arrays of quickly-deployable, targetable, weather stations which will be deployed ahead of, and into, potentially tornadic storms.

The CEE team, in collaboration with NOAA, will utilize the information collected by the ATMS team and others to assess the damage caused to the natural and built environment on the ground and through the air. From this damage, the team will determine tornado occurrence and estimate their near-surface wind speeds and characteristics.

Faculty and students in CEE and ATMS will utilize this information to improve the understanding of multi-faceted tornado risk.

Robert Trapp is Professor and Head of UIUC’s Department of Atmospheric Sciences. Trapp’s research interests include the dynamics and observations of mesoscale convective systems, severe thunderstorms, and tornadoes; mesoscale modeling and predictability.

Frank Lombardo joined the faculty of UIUC’s Department of Civil and Environmental Engineering in 2015. He is also a faculty affiliate in atmospheric sciences. His research interests are wind engineering, extreme wind characterization, bluff body aerodynamics, resilience and structural damage.