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Grimes Bridge Replacement

A concrete bridge replacement overcomes structural and environmental challenges

Innovative design... More than exceeded the client's expectations... Many aspects to showcase.

The intersection of Grimes Bridge Road with Oxbo Road, which included a bridge over Big Creek, needed improvements for numerous safety reasons. Not only did structural challenges exist, but additional complexities also arose due to the duration of the project, changing traffic patterns and restrictions from an adjacent national park. What resulted, however, was a welcome improvement for the community and a solid relationship for GS&P.



This project spanned 14 years with numerous obstacles along the way. Describe your relationship with the client as it developed and what your team did to stay in sync with the client’s needs.

Tom Ziegler: Whether it was traffic signals, lighting, the retaining walls, aesthetic treatments, public involvement or the ground-breaking ceremony, we went above and beyond. We attended meetings on a moment’s notice and were always willing to offer feedback to help the roadway folks improve their design.

From a structural standpoint, the client made several changes, but we were always willing to meet with them to make sure we were all going in the same direction, which is why GS&P is still in good standing with the City and GDOT.

Ted Kniazewycz: We also had an established relationship with the bridge group at GDOT and used our experience with people on their team to talk through issues. Again, we just tried to keep everything moving forward.

Tom: Meeting repeatedly to not only get their buy-in on framing details but also to refresh their memory as time passed.

Even though you were just responsible for the bridge, you had to coordinate data from numerous entities which added to the complexity of the project and overall design. How difficult was it to pull everything together?

Ted: The two intersecting roads definitely added to the complexity. Since we were not doing the actual roadway design, the key was to make sure we were aware of any changes made to the roadway plans throughout the project development. When you have roads coming in from different directions, they bring conflicting slopes together, so we had to study the cross-slope of the roads. As a result, we had to make several changes in our design along the way or make suggestions for changes to the roadway designer.

Most of the complications had to do with how utilities cross through the construction site to build two intersecting roads. The adjoining property is a national park, so working within the park’s restrictions meant we couldn’t impact that property at all. Our choices were severely limited. We were able to shift the alignment slightly to intersect the two roads directly over the creek that runs through the area.

If you had to pinpoint the single most daunting structural challenge on this project, what would it be?

Tom: The most complicating factor was the framing plan for the beams to support the rest of the prestressed concrete bridge. Being able to get the geometry to work and keep the footprint as small as possible was the primary issue. Every single beam in the bridge was a different size.

Ted: The structure was constructed in a way that didn’t extend beyond the roadway width. We kept the design as compact as possible and held the footprint of the structure to stay within the existing right-of-way that was available for the roadway.

Are intersecting roads over a creek a challenge?

Ted: Intersecting two roads over a creek is particularly difficult because of environmental and water quality concerns related to putting a support structure in the middle of it. We used some very unique geometry to allow us to create a uniquely shaped concrete structure that worked for bicyclists, pedestrians and traffic and did not impact the national park property.

How were you able to make adjustments for the traffic volume that increased over the lifetime of the project?

Ted: One of the major changes that occurred in the project was the need to include a traffic signal at the intersection. When the project was first conceived, the traffic volumes were not high enough to require traffic signals.

Tom: As the project progressed, development in the area increased to a point that a traffic signal was needed at the intersection on the bridge. A special bent, or pier, design was required to provide a cantilevered support for the traffic signal poles. We devised a solution to extend the ends of the pier cap out further and mount the lights directly to them.

Since you had to minimize the impact to the surrounding park and residential areas, what design elements made Grimes Bridge different from the typical bridge?

Tom: We placed a number of retaining walls both on and around the bridge that extended up the roadway and minimized the impact on the adjacent property. Way back in the beginning, our graphic artist came up with different ideas about what those could look like, and our structure guys came up with different treatments for the concrete walls going across and underneath the bridge.

Ted: There were several architectural enhancements on the bridge rail on top of the structure where lighting was embedded into the concrete. It also had different form finishes and a decorative rail on top to enhance the overall appearance of the structure so that it tied in better with the surrounding environment.

Tom: The lighting was another really unique idea that our guys came up with. We didn’t just hang a light, we used conduit and provided provisions so that you wouldn’t see the cabling and power sources. This wasn’t necessarily in our original scope, but because the client wanted it, we worked it in.

What part of this project has been the most gratifying?

Roger Bybee: I am most proud of the way GS&P professionals overcame complex design problems to create a functional and aesthetically pleasing structure which enhances the neighborhood and increases the safety of the public.

Ted: With a job that goes on for that long, there are so many details, so many conversations, and so many people. It’s really gratifying when the project is completed and you see that the owner is happy and everyone who was involved in the project and uses the project is happy. Another testimony to our success is that we are continuing to work and do some of the biggest and best projects for the City of Roswell. This experience created a long-standing relationship that has become a very successful one for us on multiple assignments. Since Grimes Bridge, we’ve done a sidewalk project as well as the first phase of the Big Creek project for them. We’ve sort of become the go-to consultant for the City now.

Tom: People were very, very concerned about what it would look like and how it would operate, and they were very pleased with the outcome. They used a substandard bridge for a long time, so some of the subtle features we incorporated made it a better performing bridge for pedestrians, bicyclists and motorists. Not only was the client happy with the end result, but it was also incredibly well received by the entire community.


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Project Info

  • Client: City of Roswell, Georgia Department of Transportation, Pond & Company
  • Location: Roswell, GA, USA
  • Market: Transportation
  • Services: Engineering, Environmental Engineering, Structural Engineering, Traffic Engineering
  • Team:
    • Tom Ziegler, P. E. Principal-in-Charge, Project Manager
    • Roger Bybee, P.E. Project Professional
    • Robin Lovett, P. E. Additional Team Members
    • Ted Kniazewycz, P. E. Additional Team Members
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