Building Bridges: Students in "Solid Mechanics" Test their Designs

Posted on November 26, 2025 by Theresa D'Orsi

"It is incredibly rewarding to see the innovative designs and witness new records in load-to-weight ratios," says Professor Yan Li, whose ENGS 33: Solid Mechanics course combines lectures, labs, and the always-engaging bridge building—and destroying—project. Through the project's four phases, students learn the essentials of stress analysis and load management, use advanced computational tools to predict performance, and build and test protoypes. "This structure aligns well with my teaching philosophy, which emphasizes critical thinking, hands-on learning, and practical application," says Li. "Students apply solid mechanics theory to design, analyze, and construct a wooden bridge that fulfills technical requirements, economic efficiency, and aesthetic appeal."

 

Photos from fall 2024 by Rob Strong '04 

Close up shot of a professor instructing a group of four students at a table in a classroom who are focused and listening.
Professor Yan Li (right) explains to a student team how they might have strengthened their prototype.

 Each of the seven bridge teams in last fall's core engineering course used SolidWorks to analyze the maximum load their design could support as well as how far the bridge roadway will bend—without breaking—at a load of 1 kilanewton (kN). At the end of the term, students—with support from MShop Instructor Joe Poissant and Couch Project Lab Manager Daniel Cullen—laser cut and glued together the various plywood parts for models they calculated would carry pedestrians and small vehicles over a river. Then the big day: Couch Lab's Instron machine put their predictions to the test. Crowding into the lab, team members and fellow students cheered as each prototype passed the 1-kN minimum load requirement and even the 4-kN mark before yielding to the crush of the Instron machine.

"Since I took over the course in 2020, I've seen clear improvements in design quality as we've learned from past challenges," says Li, who provided feedback after each test to encourage students to learn from their models' failures. "At some point, we plan to compile past designs and apply machine learning to explore further optimization possibilities. I'm curious to see if future students can outperform machine learning!"

Left image is a prototype design and right image are two students. One is holding a laser cut design and the other is working on the computer.
(1) Every design far surpassed the 1-kN minimum load requirement before being crushed by the Couch Lab's Instron machine. (2) Victoria Cubina Lopez Th'25 (left) trained in laser cutting in the MShop so she could move her team's design from Solidworks to parts, including the truss held by Victory Kumbula '26.
Three students working at a table on their laser cut design. Two students are applying glue with paint brushes while the third student looks on.
Ly Nguyen '25 Th'25 (from left), Elijah Butler '26, and Lopez painstakingly apply wood glue to parts before curing with clamps.
Group of male students looking at their laser cut design.
The team of (from left) Ben King Th'27, Nathaniel Pierce Th'27, Lawrence Martin Th'27, Jake Crawford '27, and Henry Heilman Th'27 scored a record 16.5 kNs before their design failed.
Group of students pose and smile in a classroom while holding their laser cut design.
This student team—(from left) Nguyen, Kumbula, Butler, Yehalah Fernando '26, Ava Politis '26, and Lopez—passed the 10-kN mark before trusses broke. "We had to balance force and weight," says Lopez of the grading rubric. "It was really good if it's very light and very strong, and we did a good job predicting what it can hold compared to what it really holds."

 

Bridge testing video from fall term 2025.