Researchers Create Bridge Load Rating Framework


A team of researchers from Iowa State University recently announced that it has been developing a framework to improve the efficiency, accuracy and efficacy of bridge load rating and permitting.

Brent Phares, a research associate professor from the university’s Department of Civil, Construction and Environmental Engineering, has reportedly been working on the project for the last year, with the help of a $335,000 grant from the Federal Highway Administration.

“It’s a very big job when you think about the number of bridges that exist and how things are constantly evolving throughout the many years that a bridge is predicted to last,” Phares said. “We want to make sure our estimate of the safe load carrying capacity is the most accurate and the most up to date without being overly labor intensive.”

Creating a Framework

According to the release, with over 600,000 bridges in the United States, safety and longevity are critical to safe transportation in the country. Each bridge is put through a process called “bridge load rating” every two years by mandate to test endurance and deterioration, among other factors.

However, the process can be labor intensive and costly when each bridge is inspected every two years, as well as instances where a unique vehicle needs to travel across a bridge and the bridges on the route need to be evaluated for that special instance. Consequently, the research team began to look for a process for load rating that is efficient and structure to reduce labor costs and time investments.

ISU reports that Phares has been studying bridge load rating for at least a decade, with two patents currently being licensed. The model framework reportedly provides different conceptual improvements, including the potential to alert truck drivers of a bridge’s load capacity before they reach the bridge.

“One of the things we can do with this is have a process that takes visual inspection results and seamlessly integrates them into a bridge evaluation model – that would be a huge step. Another thing we could do is make bridge models available to truck drivers, so they know what they are driving up to.” Phares said.

Additionally, the model framework covers the start of the bridge load rating, beginning with the inspection of the bridge and identifying anything that is suspect or needs repair, to analyzing that data and making changes by instrumenting select bridges with sensors and data evaluation algorithms.

“We are developing a framework for the next generation of bridge load rating – how you take information from a visual inspection of the bridge or from bridge sensors, to modifying what an analytical model would look like, to making changes and running calculations,” Phares said.

“This project covers every bit of that. We aren’t solving the issues, but we are discovering what you need to do to have an up to date, real-time and accurate system to solve these issues in the future.”

Other ISU Research

In 2019, Iowa State University engineers moved onto a second stage of testing for heated pavement, which was expected to undergo the stress of heavy truck traffic.

The technology featured electrically conductive concrete and also incorporated a concrete mix that meets highway specifications. While research began in 2015, tests started in the fall of 2016, with the installation of two 15-by-13.5-foot test slabs at the Des Moines International Airport.

Halil Ceylan—an Iowa State professor of civil, construction and environmental engineering, the Director of the Institute for Transportation’s Program for Sustainable Pavement Engineering and Research spearheaded the project.

The special concrete contains 1.25% carbon fiber, and the fibers are 1/4-inch long and about 7 millionths of a meter across by volume, conducting electricity supplied by the electrodes. Heat comes from electrical resistance in the fibers.

In 2016, with the help of a $2.2 million grant from Federal Aviation Administration’s Center of Excellence Partnership to Enhance General Aviation Safety, Accessibility and Sustainability, the team installed the aforementioned test slabs next to the airport hangar. The slabs melted snow and ice even during the coldest periods.

This prompted a bigger test inside a busy entrance to the Iowa Department of Transportation campus. This installation featured 10 heated slabs totaling 75 feet long and 24 feet wide, featuring five different configurations of electrodes, which accounts for different diameters and shapes, as well as spacing of the stainless-steel rods and bars.

When the first load of electrically conductive concrete was poured at the Iowa DOT, a crewmember was able to use a wide levelling float across the test section’s width. Ceylan noted that this was an advantage to this kind of technology: The shovels, spreaders and other equipment used were all the same kind of equipment, except for the addition of carbon fiber to the concrete.

The installation required the placement of a seven-inch base layer of standard highway concrete, then the attachment of stainless-steel electrodes to the base layer, as well as the addition of sensors and probes to the same layer. Then, finally, three inches of the electrically conductive concrete were placed on top.

Ceylan noted that the technology would most likely be suitable for small stretches of highway, such as bridge decks that are prone to icing. Funding assistance, a $360,000 grant, came from the Iowa Highway Research Board and the Iowa DOT.


Tagged categories: Asia Pacific; Bridges; Bridges; Colleges and Universities; EMEA (Europe, Middle East and Africa); Engineers; Federal Highway Administration (FHWA); Inspection; Latin America; North America; Program/Project Management; Research; Research and development; Safety; Z-Continents

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