Associate professor Washer proposes new bridge inspection standards
Since 1967, the standard schedule for bridge inspections has been once every two years according to the requirements of the National Bridge Inspection Standards. Glenn Washer is out to change that.
Washer, an associate professor in MU’s Civil and Environmental Engineering Department, recently completed a paper following five years of research with the goal of creating a more risk-based set of standards for how frequently bridges require inspections.
The rationale was to better allocate precious resources. Bridges with a lower likelihood of serious deficiencies can be inspected less, allowing more manpower, time and money to go toward bridges more in need of inspection and immediate repair.
Washer has a simple analogy to explain how this works, comparing bridges to people.
“When you’re a baby, you go to the doctor a lot, like a bridge that’s just been built,” he said. “But through most of your service life, you go to the doctor maybe every year or maybe every five years. But as you start to wear out and you’re older, you go to the doctor more often.
“The thing about bridges is there’re 600 thousand of them in the U.S., and every one of them is unique.”
The project moved in two phases. The first phase was coming up with the guidelines of how to determine the frequency of inspection. The formula Washer and his team came up with was risk being a combination of occurrence and consequence.
Occurrence in this case meant the rate at which a certain event will occur within a specific time interval. Consequence measures the impact of the event occurring in terms of a number of factors, including safety, economic impact, how repair time may affect drivers and environmental impact.
The two factors are each ranked on a scale of one through four, and the higher the combination of the two factors, the more frequent inspections need to be. The inspection schedules fell into one of four groups along the matrix, mapped out on a four-by-four scale, based on those numbers.
The second phase was testing the guidelines, which Washer and his colleagues did on bridges in Texas and Oregon. During that time, Washer also heard from and discussed the project with several officials, gaining necessary feedback.
“In some cases, there’s some hesitation to change what’s happened for 40-plus years. But in a lot more cases, this is just recognized as something that’s needed — the next step in the evolution,” Washer said. “That this is just bringing contemporary technology to the inspection process in order to do it better.”
There’s still work to be done before the proposed standard becomes the official standard, and nearly 50 years of accepted practice — known federally as 23 CFR 650 — doesn’t go by the wayside quickly. But the federal government is taking a look, with the Moving Ahead for Progress in the 21st Century Act directing the Federal Highway Administration to consider risk-based methods for inspection. That legislation, signed in 2012, dovetailed nicely with the work of Washer and his colleagues.
For now, Washer is hopeful the standards will be considered by the American Association of State Highway and Transportation Officials (AASHTO) and move forward from there.
“It’s been a very anticipated project,” Washer said. “People are looking forward to the results and hoping to be able to implement them going forward.”