Timber, steel, and teamwork: Engineering students build and deconstruct 80-ft truss bridge over water

CEEES bridge builders standing on the completed bridge

Wearing hip-waders and carrying drills, Notre Dame engineering students built an 80-ft wooden truss bridge over a narrow waterway, connecting the main campus to the quarter-acre Duck Island on St. Joseph’s Lake.

Students carry the bridge across the road to the launch site.
Students holding and attaching pieces of the bridge
Students surveying the launch area
Three male students standing on one of the piles.

The bridge project is the centerpiece of the civil engineering class, “Build, Break, Perfect,” for first-year students. Last year, the first year of the new experiential learning course, students built and deconstructed a suspension bridge on campus.

“With the construction of a full-scale bridge, students learn to deal with thousands of pounds of force,” said Luis Fargier-Gabaldón, Massman-Beavers Associate Professor of the Practice of Heavy Civil Engineering.

“Each construction site is unique and requires its own creative approach. Students learn to think like engineers.”

Working in teams throughout the semester, the students surveyed the site and then fabricated bridge modules from two-by-fours and two-by-sixes. Diagonal pieces were bolted together with small steel plates, giving the bridge the interconnected triangular arrangement characteristic of truss bridges.

First-year student Mary Elizabeth Balof, who led the fabrication team, said many challenges were confronted and resolved before construction day. “Some of the wood had split when we tried to screw it into place, and some of it was warped. So we had to address many alignment issues in fabricating the bridge.”

The finished structure, which weighed nearly 3,000 pounds, was transported to the site in three segments and then moved on rollers.

Construction on the site began at 7 a.m. on April 21.  As geese honked and ducks quacked, four students waded into the waterway to attach a lightweight structure, called a “launching nose,” on top of two piles in the waterway.

“In the water, we were responsible for making sure the bridge was aligned, and that the nose would be able to attach to the main structure,” said first-year student Lucas Brenninmeyer. “It took a lot of teamwork and some adjustments to make this work.”

Cheers broke out when the bridge and the launching nose reached the intermediate pier, 55 feet away from the mainland. From this point on, with the students pushing, the bridge could glide on rollers until it eventually reached the wooded island, a span of more than 80 feet.

By 5 p.m., planks had been laid down on the bridge to create a walkway, and students crossed their new truss bridge. By 6 p.m., the bridge had been disassembled, and the ducks and geese reclaimed their island. 

— Karla Cruise, Notre Dame College of Engineering; Photos by Wes Evard

Three students in hip-waders standing in the water attaching the bridge to the pile.
Completed bridge with students standing on the island
The truss bridge took a semester to plan and fabricate, 9 hours to build and launch, and an hour to deconstruct.