In Fall 2021, our student chapter was approached by the UMass Amherst Physical Plant about replacing the decking on a footbridge near McGuirk stadium. At the time, the bridge was out of service and in dire need of repair. The existing wood decking was rotting, and holes were visible to the small stream situated below! The university had decided it was time to replace the decking entirely after a series of intermittent patch work. We (The UMass AGC student chapter) happily accepted this project, seeing it as a great opportunity to volunteer on a campus project and learn about the materials and design involved with pedestrian bridges of this scale.
In November we officially kicked off our bridge project and went onsite to take measurements and pre-construction photos. We confirmed that the decking needed to be replaced and began thinking about new decking. At this time we presented to the body of our student chapter this exciting opportunity to get involved and procure ideas and inspiration from our members.
Planning
After visiting the bridge to take measurements and documentation photos, we sketched out bridge measurements and drafted some drawings with dimensions. We did some research on the bridge and found that it is a Pony Truss bridge, which is a bridge without lateral cross braces that allows traffic through the truss. In New England, truss bridges were fabricated using triangle shaped supports until the early 1900s.
In 2008, Drs. Alan Lutenegger and Sanjay Arwade received a $150,000 National Science Foundation grant for a bridge rehabilitation project where 85 engineering students got hands-on experience in repairing and relocating at least two old iron and steel truss bridges on footpaths. This project was called The Adaptive Use Bridge Project. Repurposing and preserving smaller historic bridges for pedestrian uses is not uncommon in New England, but this project was a unique opportunity as it provided an education opportunity for structural engineering students at UMass Amherst. Often, hands-on experience is minimal for students as projects can be too large and inaccessible. The students measured the bridge, used computer-assisted design software to create accurate plans and drawings, identified parts that needed refurbishing, cut the steel truss, prepared notches and bolt holes, fabricated a new parts, added new decking and side rails, created site plans for a foundation at the new location, and estimated how much the deck would deflect under a heavy load. We read “Material Characterization and Structural Response of Historic Truss Bridges” (Kelton, 2010) which performed load tests on the bridge and analyzed its response under different loading conditions.
There are many benefits to bridge restoration. A primary benefit is the preservation of historical structures; structures from different time periods hold cultural significance, tell stories, and allow present and future generations to connect with the ones before. Humans develop bonds with the places we live in, so there is a sentimental connection that also must be acknowledged. In addition to cultural and historical preservation, bridge repurposing is highly sustainable as it saves costs, reduces waste, and reduces the use of new materials. Repurposing can save over 80% percent of the cost of purchasing new beams, and by simply changing the loads and type of traffic the bridge receives, we can extend its service life.
When repurposing a bridge, it is important to consider its condition and strength. Often, if a bridge is supporting the loads from many vehicles, the strength shouldn’t be an issue if it is being repurposed for foot traffic, unless the bridge was removed due to poor performance or safety issues. In this way, relocating bridges to places where it receives drastically less service loads is a great way to extend its service life, but performance and safety must be considered. Corrosion is one thing to look out for. When relocating bridges, one should also consider the distance and method of transport. If the bridge is too far from its new proposed location, it could be inefficient to move it.
Material Selection and Research
We met with our members in December 2021 to discuss material selection. We considered new wood, fiber-reinforced polymer (FRP), asphalt, and metal grating. In material selection we considered cost, load capacity, lifespan, maintenance, installation method, and product availability. We ultimately decided on FRP decking for its low-maintenance, high strength, and long lifespan. Instead of replacing wood decking every ten years, we wanted to install a product that would be long lasting and cost and time efficient in the long run. FRP is argued to be more sustainable than concrete, iron, and steel, and its lighter weight makes transportation easier, cheaper, and less impactful to the environment. Additionally, the lumber market was scarce during the time we were hoping to purchase a material (post-COVID).
Over the next few months we researched different FRP suppliers and reached out to various companies with our requirements. With the recommended products, we examined material catalogs and refined our options based on load requirements, L/D ratio, and allowable deflection. After setting our technical requirements, getting a P.E. to stamp drawings, and navigating the bid process at our university, we submitted a purchase order for 420 feet of fiber-reinforced polymer (FRP) bridge decking.
Our decking can support a concentrated load up to 5,982 pounds for a width of 36″ and an L/D ratio of 240. The decking can support a distributed load of 1,414 lb/ft2 which is more than capable of an assumed load of 100 lb/ft2 for a pedestrian walkway. We were confident and excited for our decking to arrive in Amherst!
Work and Installation
Awaiting the decking, we had a crane lift the bridge from its foundation and set on jersey barriers nearby. This way we could further evaluate the bridge’s conditions comfortably and inspect points that were otherwise inaccessible when mounted over the stream. During this period, the existing, rotting, decking was removed and disposed of. The steel was blasted to remove traces of lead that were discovered, and then the steel was primed and painted to be ready for the installation of our decking!
Before:
After:
When working on the purchase order for the FRP decking, the supplier informed us that the FRP planks are manufactured in lengths of 20′. The existing width of the decking was 12′, meaning 8′ planks would be leftover and unused. We devised a plan to modify the bridge stringers to reduce the span of the planks to 10′. This way, the FRP planks could be cut in half, thereby cutting the cost in half (saving over $20,000). Additionally, this gave us experience breaking the welds with angle grinders and rewelding the stringers to the bridge. The Physical Plant rewelded the stringers afterwards.
This process was simple and precise. We employed two angle grinders to tear the welds from the larger structural steel attaching the I-beams to the truss. We spent a few hours grinding away a relatively clean cut that didn’t disturb the old steel. Our advisors and CEE lab technician were of great assistance in this process as we had no metal work experience prior.
We created and hung a banner to inform the public what was happening. Public engagement and inclusion is key on construction projects! We inspected the concrete bridge foundation and concluded that it was in very good condition.
Decking installation!
After touching up some paint spots and inspecting the decking installation, we installed a wood buffer to fill the gaps between the new decking and the handrail.
We contracted a crane operator to return the bridge to its foundation and handed custody of this campus bridge back to the Physical Plant for them to complete some finishing touches to the walkway approach before reopening to the public.
Celebration and Reflection
Looking back on the campus bridge rehabilitation project, it’s incredible to see how much we have accomplished as a team and as individuals. From the early days of fall 2021 when we were approached with this opportunity, to now, as the bridge stands rehabilitated and ready for use, we have learned invaluable lessons that will stay with us for a lifetime and had many laughs and cries along the way ?
First and foremost, the planning phase was crucial to the success of the project. Taking measurements, researching the bridge’s history, and understanding its significance in New England’s cultural heritage provided us with a deeper appreciation for the task at hand. Learning about The Adaptive Use Bridge Project, where other students had gained hands-on experience in preserving historic bridges, inspired us to take on this challenge with enthusiasm and determination as hungry undergraduates in an engineering program like ours at UMass.
One of the most significant aspects of the project was the material selection and research phase. It taught us the importance of sustainability and the impact of our choices on the environment and how it is all governed by cost. Opting for fiber-reinforced polymer (FRP) decking not only ensured a longer lifespan and low-maintenance but also showcased our commitment to eco-friendly solutions. Navigating the bidding and purchase process at the university was an eye-opener, revealing the complexities of managing even a relatively small-scale project. The process of optimizing the decking dimensions was a turning point in our journey. Making modifications to the bridge and coming up with a cost-effective solution not only saved a substantial amount of money but also gave us hands-on experience in metalwork. It was a moment of pride and satisfaction, seeing our efforts come to fruition.
As we reflect on the entire journey, we can’t help but feel an overwhelming sense of accomplishment and hope that future members of the UMass AGC student chapter are able to be given an equal or larger project opportunity to learn and grow. We have learned not only about bridge rehabilitation but also about the importance of sustainability, historical preservation, and teamwork. The skills and experiences gained during this project will undoubtedly shape our futures as engineering & construction professionals and as responsible members of society. As we celebrate the completion of this project, we carry with us the knowledge that every little effort counts, and we can make a difference in our community for years to come!
Finished Bridge
Special Thanks To…
Dr. Scott A. Civjan, Dr. Zachary Westgate, Mark Gauthier, Pamela Monn, the Physical Plant, and the AGC officers and members involved:
Sam Esquivel – CEE ’23
Nate Wright – CEE ’23
Noah Green – CEE ’23
Sean McDonough – CEE ’25
Evelyna Legkodukh – CEE ’22
Varuna Desai – CEE ’25
Oskar O’Hara – CEE ’22
Max Harkness – CEE ’24
Tom Toscano – CEE ’25
Oliver Pullin – BCT ’24
Kitty Lovell – CEE ’23
Brigham Stevenson – CEE ’25
Kai Grocki – CEE ’24
Ethan French – CHEM ’23
Reference: Kelton, Sean L, “Material Characterization and Structural Repurpose of Historic Truss Bridges” (2010). University of Massachusetts Amherst, Masters Theses 1911 – February 2014. 448.
Fun Bridge Content
The work you have completed on the Bridge is absolultely amazing. I have really enjoyed reviewing all of the stages of your project as well as the video, really inspiring. Thank you so much for sharing this, I think its time my community in Wales did things like this :)
Keep up the great work
Thank you Helen for your comment, it means a lot to our chapter!