It takes only a glance at the news to find evidence of America’s aging—and at times failing—roadway infrastructure, from relatively minor pothole problems to tragic bridge collapses. Couple the advancing age of the nation’s roads and bridges with a trend toward declining revenues for replacement projects, and government agencies find themselves tasked with developing new and creative ways to preserve existing structures and extend their service life.
In one such case, the Tennessee Department of Transportation (TDOT) engaged GS&P in an engineering-design effort to rehabilitate a set of heavily used bridges along Nashville’s Interstate 440—bridges that were originally constructed in the 1970s and ’80s, and were showing their age through increasing deck damage and deteriorating expansion joints.
I-440 is a four-lane divided bypass loop south of downtown Nashville that spans 7.5 miles around Interstate 40, bisects Interstate 65 North and South, and provides exits to several bustling parts of town, including Hillsboro Road/Green Hills, West End Avenue/Vanderbilt University and Nolensville Road. The GS&P design team assigned to this maintenance and preservation project drew inspiration from knowing that these much-needed improvements would help ensure safer roadways for Nashville drivers and travelers passing through Music City for years to come.
“Our team has worked on many repair projects for TDOT and other entities, so we really have a keen understanding of the importance of preserving the existing infrastructure, primarily because of the reduced availability of funding,” says senior structural engineer and project leader Ted Kniazewycz.
“We knew this project had the potential to address issues that would extend the bridges’ service life for many years, prevent damage, and reduce the potential for future deterioration,” he says. “The way things are today, a lot of infrastructure is really getting old, and we’re seeing failures in multiple places. These particular bridges have quite a bit of life on them. So anything we can do to extend that life, especially in this time of tight budgets, is really crucial.”
Senior transportation engineer and project manager Mark Holloran notes that the design team’s well-established rapport with TDOT proved vital to the bridge rehab work.
“This close partnership was the catalyst to a very successful project that will provide motorists with reliable, low-maintenance structures for years to come,” says Holloran. “Our team coordinated closely with TDOT’s Bridge Inspection and Repair Office in both the development of the repair plans for these bridges, and in the fieldwork that was required during construction, including the identification of the specific areas of the bridge structures to be modified for improved inspection access.”
Safety & Savings
The comprehensive project called for making repairs that would lessen the chance of accelerated damage to the bridges and minimize the need for annual maintenance work. As critical as it was to stretch the state’s coffers, cost wasn’t the first consideration when it came to designing the bridge improvements.
“From the engineering side, public safety is always the No. 1 thing we think about when we do any project,” Kniazewycz says. “It’s not that any of these bridges were at risk of failing immediately, but we knew that the work would extend their life even further into the future.”
In today’s recovering but still-fragile economy, savvy taxpayers are watching every dime spent on public projects. In light of budget considerations, the design team employed innovation and standardization to make the bridge repair plans as efficient and cost-effective as possible.
The team’s task became complex early in the project development, when what was initially a single bridge engagement grew to 14 separate structures along I-440—none of which were originally designed or built alike. To meet the challenge, the GS&P team created bridge-specific removal plans and then incorporated standardized repair details for all of the bridges. This pivotal step allowed the contractor to have many of the necessary replacement items identically fabricated, thereby reducing costs and making installation for field crews more seamless.
“We developed the plans so the details and the items used by the team members in the field would all look similar between the bridges,” Kniazewycz says. “The challenge for us was that the original bridges were each designed by a different person. In the bridge world, people like to put their own twist on a design. When you want to improve multiple structures that are all very different, it means the team has to look at those bridges as a whole and see how we can make the repairs similar so the contractor and their crew know the procedures, and have the right equipment and tools regardless of which bridge they’re working on. That way, they don’t have to relearn on every bridge, and they can get more efficient as they move from bridge to bridge.”
For example, many of the I-440 bridges’ original design differences involved their decks’ expansion joints. And some bridges had sidewalks while others did not, a factor that complicated joint installation and called for a unique solution.
As Kniazewycz explains, “The existing aluminum expansion joints experienced several modes of failure, including fatigue fracturing of the metal plates, and tear failure of rubber membrane within the joint system. This membrane was critical in preserving the overall condition of the bridges. The failed joints allowed water and road debris to clog the expansion gaps, leading to cracked concrete sections and deterioration of the substructure concrete.”
The team’s solution hinged on the installation of new, hardened steel joints and expansion membranes that would eliminate the leakage of salt-laden runoff onto substructure concrete.
“The new steel joint system is not as likely to experience fatigue issues, and the system is designed to allow for the replacement of the expansion membrane in case there is a tear in the future,” Kniazewycz says.
The required modifications included removal of some sidewalk portions and bridge railings, installation of a new joint system, and reconstruction of rails and sidewalks. As a safety measure, and to ensure compliance with ADA requirements, a steel slider plate was installed flush with the sidewalk to eliminate any tripping hazard.
Keeping Traffic Moving
As in all large U.S. cities, Nashville’s roadways have become increasingly busy, making it especially difficult to repair 14 bridges across a 7.5-mile stretch of highway without severely disrupting traffic flow.
TDOT is keenly aware of public concerns about traffic during construction projects, and the department routinely schedules maintenance projects at night and on weekends. However, in urban settings such as the I-440 corridor, weekend traffic can be as congested as rush-hour traffic.
To help minimize congestion, the design team worked closely with Nashville Metro Public Works—which controls local roads and signal timing—to develop site-specific plans and lane assignments that would favor peak traffic movements during weekend construction cycles. These plans, along with detailed detour signage and advanced notification of project schedules, eased traffic congestion. In addition, the contractor was able to complete several work tasks during weeknight hours when traffic was the lightest in the area.
“Understanding how Public Works operates was a benefit to us, because we know how they do street closures, when they like to do them, and how long to do them,” Kniazewycz says, “and we prepared detailed plans to provide specific traffic movements on the local roads during the construction projects. In areas of high traffic—like at the Nolensville Road and Hillsboro Road exits—we knew we couldn’t close roads completely. So we developed a plan to shift traffic that allowed the contractor to work while maintaining traffic flow at the same time.”
In addition, the team built in detailed plans for ‘smart’ detours that routed drivers around the work and made sure two adjacent bridges were not closed at the same time.
The design team delivered a cost-effective solution for a complex set of requirements, preserving state dollars, while adding years to the life of the bridges along a vital roadway. The design portion of the project was completed on schedule and under budget, and construction work was completed ahead of schedule and within budget.
In total, crews installed some 200 access portals, 1,800 linear feet of expansion joints, 20,000 square feet of deck seal and 6 miles of permanent roadway striping; replaced 4,000 square feet of sidewalk; and applied 500 gallons of sidewalk sealer.
“I don’t know of any issues that came up during the duration of this project,” Kniazewycz says. “I think it was very well communicated and executed by the contractor. There was another construction project on I-440 at the same time, and we were able to modify our plans to allow the two projects to be carried out simultaneously without impacting either one negatively.
“I think our approach to standardize the details of the design and construction as much as possible, and to ensure traffic control, all helped to keep things moving and ensured a successful result.”