St. Stephen’s Physics Instructor Crosses a Spaghetti Bridge From Austin to Boston

One of Danielle Horton’s physics and engineering spaghetti bridges lab received national attention recently at the American Association of Physics Teachers conference in Boston. The conference drew over a thousand educators who were eager to learn innovative curriculum ideas and observe lab demonstrations that they could implement into their own classrooms. Horton was one of a handful of educators along with Harvard and MIT professors who delivered a presentation.

 

“It was a fantastic experience and I plan to incorporate some new labs, demos, and content into my teaching this year,” says Horton, St. Stephen’s physics and engineering teacher. “My presentation about my spaghetti bridge project was really well received. I left the conference inspired and excited to teach.”

Horton says her hands-on engineering labs, using raw spaghetti noodles and hot glue to build a truss bridge, was well received at the conference. The lab, as noted in Horton’s Abstract, is designed to to deepen a student’s understanding of the role of force distribution in truss bridges under static loading. Spaghetti is used due to its behavior under stress and strain as well as ease in multiple iterations. 

“Spaghetti actually experiences stress and strain in a way similar to steel, allowing students to see how trusses distribute tension and compression,” says Horton. “It [spaghetti] is inexpensive, but more importantly, it is superior when students do their mathematical analysis and test it, using the Vernier Structures and Materials Tester, to achieve the greatest static load-to-weight ratio.”

Horton continues, “It's called a truss analysis, and it indicates which member of the truss is most likely to fail first. In contrast, balsa wood always breaks at a joint and is dependent on how well students glued it together,” explained Horton.  

Aided by computer design, some wax paper and a glue gun, the spaghetti bridges are easier to construct.  Horton says that 98% percent of the time, the piece that breaks exactly matches what student calculations predicted. This creates the “aha moment” that applied math matters.

By the time her students tackle the bridge project, they have investigated more than 10 types of trusses. They also have an understanding of the mechanics, and the distinct advantages over other bridge building materials like balsa wood.. 

 

Horton’s spaghetti bridge lab is not only applicable and an important physics and engineering lesson in the Upper School but also the perfect college preparatory as told by one of her former students, Louis Layton ’23, who says he was more than prepared while sitting in his first-year statics class at the University of Wisconsin-Madison. The course, a branch of classical mechanics, focuses on the analysis of force and torque acting on a physical system that does not experience an acceleration, but rather is in equilibrium with its environment. 

“We did the same truss analysis I had previously learned in Ms. Horton's class,” said Layton.

 

Designing and rapid prototyping spaghetti bridges in a high school engineering class allows students to deeply understand the role of force distribution in truss bridges under static loading.  Spaghetti is used due to its behavior under stress and strain as well as ease in multiple iterations.  Students investigate > 10 types of trusses in order to design their own truss bridge. A truss analysis is then conducted on their design and potential weaknesses are identified.  The bridge is tested to failure, using the Vernier Structures and Materials Tester, with the goal of achieving the greatest static load to weight ratio.  After testing, a failure analysis is completed and modifications are made to improve the strength to weight ratio.  The bridge is re-tested.  Students then analyze the results, compare their truss analysis to the location(s) of bridge failure, provide suggestions for a future bridge design, and disseminate their findings through a recorded presentation.  

In this lesson, students learn the basics of the analysis of forces engineers perform at the truss joints to calculate the strength of a truss bridge. This method is known as the “method of joints.” Finding the tensions and compressions using this method will be necessary to solve systems of linear equations where the size depends on the number of elements and nodes in the truss.